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Bioavailability and toxicity of pyrene in soils upon biochar and compost addition
Abstract
Compost (10%) and biochar (5%) amendment to soil is not toxic to C. elegans. • EC50 Reproduction for pyrene were 14 and 31 mg/kg (soil dry weight) for two different soils, respectively. • Combined addition of compost and bio-char most effectively reduced porewater concentrations and toxicity of pyrene. • The porewater concentration predicted 52% of pyrene toxicity to nematodes. The study investigates the role of biochar and/or compost in mitigating the toxic effects of pyrene in soils using reproduction of nematodes and porewater concentration as measures of pyrene toxicity and bioavailability, respectively. Two soils were spiked with increasing levels of pyrene to achieve a concentration-response relationship for the reproduction of Caenorhabditis elegans. The observed EC50 values (pyrene concentration causing 50% inhibition of reproduction) were 14 mg/kg and 31 mg/kg (dry mass) for these soils, corresponding to equilibrium porewater concentrations of 37 μg/L and 47 μg/L, respectively. Differences in organic carbon content were not sufficient to explain the variability in toxicity between the different soils. Soils causing a significant inhibition of reproduction were further amended with 10%-compost, 5%-biochar, or both, and the effects on reproduction and porewater concentration determined. Combined addition of compost and biochar was identified as the most effective strategy in reducing pyrene concentration in soil porewater, which was also partly reflected in soil toxicity. However, porewater concentrations predicted only 52% of pyrene toxicity to nematodes, pointing to particle-bound or dietary exposure pathways. Capsule: Amending pyrene-spiked soil with biochar and compost effectively reduced pyrene porewater concentrations and toxicity to nematodes, which were significantly related.
... In particular, two recent studies have suggested that combining biochar and compost amendments to soils contaminated with polycyclic aromatic hydrocarbons may be successful to significantly reduce toxicity to soil organisms e.g. Caenorhabditis elegans (Bielská et al., 2017), while avoiding the full inhibition of the degradation process (Sigmund et al., 2018). Both studies suggested that changes in toxicity and degradation occurred through changes in the contaminant sorption, but details regarding the process were limited to data obtained at relatively high concentrations and/or in the presence of multiple contaminants. ...
... Pyrene was selected as a model organic contaminant representative of polycyclic aromatic hydrocarbons. The study design directly builds on the results of Bielská et al. (2017) and Sigmund et al. (2018), and focuses on aspects identified as requiring further investigations. ...
... Compost is typically very rich in organic matter (>20%, Brinton, 2000), and may produce dissolved organic matter that can facilitate the transport and uptake of sorbed contaminants. For instance, the results of Bielská et al. (2017) indicated a possible contribution of particle-bound pathways to toxicity. Sorption is typically measured using the batch method, which includes a phase separation step often based on centrifugation. ...
Amendment with biochar and/or compost has been proposed as a strategy to remediate soil contaminated with low levels of polycyclic aromatic hydrocarbons. The strong sorption potential of biochar can help sequestering contaminants while the compost may promote their degradation. An improved understanding of how sorption evolves upon soil amendment is an essential step towards the implementation of the approach. The present study reports on the sorption of pyrene to two soils, four biochars and one compost. Detailed isotherm analyzes across a wide range of concentration confirmed that soil amendments can significantly increase the sorption of pyrene. Comparisons of data obtained by a classical batch and a passive sampling method suggest that dissolved organic matter did not play a significant role on the sorption of pyrene. The addition of 10% compost to soil led to a moderate increase in sorption (<2-fold), which could be well predicted based on measurements of sorption to the individual components. Hence, our result suggest that the sorption of pyrene to soil and compost can be relatively well approximated by an additive process. The addition of 5% biochar to soil (with or without compost) led to a major increase in the sorption of pyrene (2.5–4.7-fold), which was, however, much smaller than that suggested based on the sorption measured on the three individual components. Results suggest that the strong sorption to the biochar was attenuated by up to 80% in the presence of soil and compost, much likely due to surface and pore blockage. Results were very similar in the two soils considered, and collectively suggest that combined amendments with compost and biochar may be a useful approach to remediate soils with low levels of contamination. Further studies carried out in more realistic settings and over longer periods of time are the next step to evaluate the long term viability of remediation approaches based on biochar amendments.
... The amendment rates were selected on the basis of results obtained from degradation and sorption pre-experiments (data not included), together with published information on the immobilization of heavy metals with biochar [22,23]. The characteristics of the soil mixtures were determined in a previous study [24]; they are shortly presented in Section 3.1 of this paper and Table S-1 in the Supporting information. Elemental compositions of the soil mixtures were also measured using an elemental analyzer (CHNS Elementar Vario MACRO). ...
... The same soil mixtures were previously used by Bielská et al. [24] and their characterizations are presented in Table S-1 in the Supporting information. The C/N ratio, which is an indicator of N availability, remained largely unchanged following 10% compost addition and was in the lower part of the range reported for similar soils [33], indicating that the (agricultural) soils used in this study had a high N availability. ...
... This is consistent with results obtained by Marchal et al. [21] who found that biochar reduced the degradable phenanthrene fraction in soil. Bielská et al. [24] also found a lower pyrene bioavailability and toxicity following the addition of biochar to the same soil-compost mixtures. ...
Diffusely contaminated soils often remain untreated as classical remediation approaches would be disproportionately expensive. Adding compost can accelerate the biodegradation of organic contaminants and adding biochar can immobilize contaminants through sorption. The combined use of compost and biochar to reduce polycyclic aromatic hydrocarbon (PAH) and NSO-substituted PAH contamination has, however, not previously been systematically investigated. We have therefore investigated the processes involved (i) through sorption batch experiments, (ii) by monitoring changes in bacterial, fungal and archaeal communities using denaturing gradient gel electrophoresis, and (iii) through degradation experiments with fluorene, phenanthrene, pyrene, carbazole, dibenzothiophene, and dibenzofuran. Sorption coefficients for organic contaminants in soils increased tenfold following 10% compost addition and up to a hundredfold with further addition of 5% biochar. The rate of PAH and NSO-PAH degradation increased up to twofold following compost addition despite increased sorption, probably due to the introduction of additional microbial species into the autochthonous soil communities. In contrast, degradation of PAHs and NSO-PAHs in soil-compost-biochar mixtures slowed down up to tenfold due to the additional sorption, although some degradation still occurred. The combined use of biochar and compost may therefore provide a strategy for immobilizing PAHs and NSO-PAHs and facilitating degradation of remaining accessible contaminant fractions.
... Hussain et al. (2018) (Hussain et al., 2018) applied biochar made from green garden waste at 500°C for the degradation of petroleum hydrocarbons. Bielská et al. (2017) (Bielská et al., 2017) studied effective pyrene removal from soil by biochar made at 550°C. ...
... Hussain et al. (2018) (Hussain et al., 2018) applied biochar made from green garden waste at 500°C for the degradation of petroleum hydrocarbons. Bielská et al. (2017) (Bielská et al., 2017) studied effective pyrene removal from soil by biochar made at 550°C. ...
Biochar is the thermal degradation product of biomass generated in an oxygen-limited environment under different pyrolysis conditions. Biochar characteristics are functions of the feedstock material and pyrolysis temperature. Depending on pyrolysis conditions biochar concentrates varying quantities of recalcitrant and labile carbon along with nutrients which in turn affect soil physiochemical properties and microbial processes. Biochar in soil balances carbon content encourages nitrogen fixation and solubilize phosphorus along with enhancing soil enzyme activity. It serves as a microhabitat for microorganisms present in soil thus influences the diversity, composition, and distribution of soil microbial communities by affecting their intra- and interspecific communication. This review provides an overview of the current knowledge about biochar characteristics, its interactions with soil, and associated biota and its role in soil remediation. In addition, this paper also discussed the factors affecting the capacity of biochar to adsorb organic pollutants following different mechanisms. Being an effective adsorbent due its high specific surface area, large porosity, and numerous surface functional groups biochar has been explored extensively in field of environment to remediate contaminated soils.
... In addition, An Agilent Eclipse XDB-C18 column with a Thermo Scientific TSQ Quantum Access Max was used for Fenoxaprop-ethyl and Fenoxaprop HPLC-MS/MS analysis. Smaller particle column separations improve efficiency per unit time;however efficiency cannot be improved at greater mobile phase flow rates or linear velocities [32]. Moreover, the detector on the mass spectrometer was configured to ESI. ...
... Equipped with ion sweep gas pressure along with sheath gas pressure (0,15,35 arb) and auxiliary gas pressure with a spray voltage (2500 V). with a temperature of 200 and 300 celsius by the vaporizer and capillary, along with recoveries for fenoxaprop-ethyl and fenoxaprop 0.1,1, and 10 g was in between of 85%:102% with the control soil and 83%:106% in the biochar amended soil [27]. This equation (Ct = A1 + A2ekt) was utilized [27,32]. ...
Fenoxaprop-ethyl Herbicide is a postemergence herbicide that is used in soil for the control of pests and wheat. Unfortunately, it is also notable to cause alarming risks to humans, animals, and plant life. Nevertheless, the application of biochar additions to soil could promote the decline of chemical contaminants in the soil ecosystem. In this review, fenoxaprop-ethyl toxicity, with the use of soils and biochar, were evaluated. It was concluded that the utilization of the amendment of biochar on heavy metals in soil can be beneficial as a remedy in farming procedures since it can be a useful method for the improvement of the quality of agricultural productivity. It could be a valuable technique for improving soil quality and environmental sustainability.
... Biochar (BC) interacts with pesticides by sorption and sequestration of pesticide residues, but it also can support their degradation indirectly (Liu et al., 2018;Safaei Khorram et al., 2016). This changes pesticide concentrations in soils, their partitioning between soil, pore water, and biota, and consequently their bioavailability/bioaccessibility and bioaccumulation in the soil organisms and plants (Oliveira et al., 2017;Bielská et al., 2017;Marchal et al., 2013;Reid et al., 2013). Furthermore, this alters pesticide input to trophic chains, toxicity and risks, and efficiency to pests (Bielská et al., 2017;Ahmad et al., 2014). ...
... This changes pesticide concentrations in soils, their partitioning between soil, pore water, and biota, and consequently their bioavailability/bioaccessibility and bioaccumulation in the soil organisms and plants (Oliveira et al., 2017;Bielská et al., 2017;Marchal et al., 2013;Reid et al., 2013). Furthermore, this alters pesticide input to trophic chains, toxicity and risks, and efficiency to pests (Bielská et al., 2017;Ahmad et al., 2014). The effects of BC on the bioavailability of pesticides are not straightforward as, on the one hand, BC may diminish a pesticide's degradation due to its increased sorption to BC, while, on the other hand, BC can stimulate microbial activity in the soil and thus promote the same pesticide's degradation (Liu et al. 2018). ...
The study showed novel findings about changes in the fate and bioavailability of conazole fungicides (CFs) after biochar (BC) addition to soil. Two contrasting soils (low- and high-sorbing of CF; L soils, H soils) were amended by three BCs (low-, moderate-, and high-sorbing of CF; L-BC, M-BC, H-BC) at 0.2% and 2% doses. Epoxiconazole (EPC) and tebuconazole (TBC) were then added to the soil–BC mixtures, and their degradation, bioaccumulation in earthworms (Eisenia andrei), and bioconcentration in lettuce (Lactuca sativa) were studied for three months. Also, stir bar sorptive extraction (SBSE) was performed to determine CF (bio)accessibility. The EPC and TBC degradation in the soil–BC mixtures followed usually the first-order decay kinetics. The BC addition prevalently decreased the pesticides degradation in the L soil mixtures but often increased it in the H soil mixtures. In general, EPC degraded less than TBC. BC type and dose roles in the pesticides degradation were unclear. The BC addition significantly reduced pesticide uptake to the earthworms in the L soil mixtures (by 37–96%) and in the H soil mixtures (by 6–89%) with 2% BC. The BC addition reduced pesticide uptake to the lettuce roots and leaves significantly—up to two orders of magnitude, and this reduction was strong in H soil mixtures at 2% of BC. The BC addition reduced the CF (bio)accessibility measured by SBSE in all L soil mixtures and some H soil mixtures with 2% BC. Although not significant, it also seems that the pesticide bioaccumulation, bioconcentration, and (bio)accessibility were decreasing according to the BC type (L-BC > M-BC > H-BC). The pesticide concentrations in the earthworms and lettuce correlated significantly to the SBSE results, which indicates this technique as a possible predictor of biotic uptake. Our results showed that the interactions were hard to predict in the complex soil–BC–pesticide system.
... 16 Another common PAH, pyrene, reduces the reproduction rates in nematods. 17 Benz[a]anthracene and benzo[b]fluoranthene inhibit antioxidant capacity, which causes lipid peroxidation and cell damage. 18,19 Chrysene is another toxic PAH that antagonizes the estrogen receptor and causes cardiac malformations, as well as ocular and circulatory defects in aquatic organisms. ...
... 35 The value of HLB provides information on whether a surfactant produces oil in water or water in oil emulsion. The surfactants with low HLB values (3-6) are lipophilic and form water in oil emulsion, whereas those with high HLB (10)(11)(12)(13)(14)(15)(16)(17)(18) are hydrophilic in oil in water emulsion. 36 Classification of surfactants by HLB values aids in the selection of the best surfactant for various applications. ...
Soil contaminated with hydrophobic organic hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), pose a serious threat to the ecosystem and human health. Moreover, the sorption and desorption of the PAHs, due to the interaction with the soil organic matter (SOM) and other contaminants, greatly affect the fate and mycoremediation efficiency of the contaminated soil. On the other hand, the application of surfactants with or without additives for the mobilization of PAHs from contaminated soil has garnered increasing attention for soil remediation. In this context, several commercial surfactants and biosurfactants were reported either as soil flushing agents or soil additives, followed by either in situ or ex situ mycoremediation of the PAHs from contaminated soil. Hence, for a successful implementation of surfactants for mycoremediation of contaminated soil, a comprehensive introspection on its chemistry and mechanism is necessary. Thus, this review focuses primarily on understanding the effect of surfactants and the mechanism of desorption of PAHs from the soil. This work also emphasizes the effect of surfactants on the efficiency of mycoremediation of contaminated soil. Further, the review summarizes various surfactant‐assisted mycoremediation strategies of contaminated soil. Finally, the limitations of surfactant‐assisted mycoremediation, precipitative, and partitioning loss, along with toxicity of the surfactants, were reviewed. Thus, this review will aid in understanding the underlying mechanism and efficiency of surfactant‐assisted mycoremediation and it also proposes current research trends to improve the efficiency and enhance the bioremediation of PAHs‐contaminated soil. © 2021 Society of Chemical Industry (SCI).
... The results indicate improved bulk density and increases in active car- bon and potential nitrogen mineralisation compared with una- mended soil (Sax et al., 2017). For these reasons, some authors have developed systems that obtain a compost-like biochar ( Agegnehu et al., 2016) or work with mixed mature compost with biochar added to the soil ( Agegnehu et al., 2016;Bielská et al., 2017). Bielská et al. (2017) showed that the joint use of compost and biochar was successful in the sorption of pyrene from contam- inated soils and promoted the development of a model nematode. ...
... For these reasons, some authors have developed systems that obtain a compost-like biochar ( Agegnehu et al., 2016) or work with mixed mature compost with biochar added to the soil ( Agegnehu et al., 2016;Bielská et al., 2017). Bielská et al. (2017) showed that the joint use of compost and biochar was successful in the sorption of pyrene from contam- inated soils and promoted the development of a model nematode. In some cases, biochar has been proposed as a co-substrate for the composting process itself of FW or agricultural residues ( Khan et al., 2016;Vandecasteele et al., 2016). ...
The aim of this study is to investigate the possibility of using cerium oxide (CeO2) nanoparticles (NPs) attached to reduced graphene oxide (rGO) as an alternative adsorbent for cadmium (II), lead (II) and chromium (VI) removal from aqueous solution. The new nanomaterials (CeO2/rGO) were obtained following two different strategies, in-situ growth and self-assembly approach. The adsorption capacities for each heavy metal were investigated at a fixed pH (5.56), a range concentration of heavy metal from 5 to 250 mg/L and a fixed concentration of 0.05 mg of CeO2/rGO nanomaterial. The experimental data were fitted using the Langmuir, Freundlich and Temkin isotherms models. The experimental data of each nanomaterial for the removal of Pb(II) were approximated best by the Langmuir model, while for the removal of Cd(II) Langmuir and Freundlich showed good regression coefficients. The study showed that CeO2 NPs attached to rGO could be used as an efficient adsorbent material for the adsorption of cadmium and lead from aqueous solution. The nanomaterial obtained by in-situ growth registered the highest adsorption capacity for the removal of lead (95.75 mg Pb²⁺/g CeO2/rGO-HMT), while in the case of cadmium the highest adsorption was obtained with the nanomaterial synthesized following the self-assembly approach (31.26 mg Cd²⁺/g CeO2/rGO-AM).
... In addition, less attention has been paid to the effects of biochar on toxicity of pesticides to soil biota [17]. Earthworms, an essential part of the soil fauna, make direct and indirect contributions to soil ecosystems, such as soil structure, fertility, microbial biomass and enzymatic activity [18]. ...
... In the biochar-amended treatment, the dose of biochar was set at 5%, corresponding to 25 g of biochar and 475 g of the soil weighed. The applied dose of biochar corresponds to the doses administered in other studies conducted with biochar [17]. The concentrations of fenoxaprop-ethyl in both treatments were set at 10 µg g −1 by mixing 1 ml of 5000 µg ml −1 of fenoxaprop-ethyl acetone solution. ...
Biochar, as a soil amendment in agriculture, has attracted considerable attention. In the study, the fate and toxicity of the herbicide fenoxaprop-ethyl were evaluated in soils with and without 5% rice husk biochar amendment. Fenoxaprop-ethyl and metabolite fenoxaprop degradation followed first-order kinetics in the two soils. Fenoxaprop-ethyl decreased fast with half-lives less than 2 days. Large amounts of fenoxaprop formed and remained in the control soil. However, fenoxaprop was much lower in the biochar-amended soil with reduction over 85% on the 35th day. The estimated half-lives of fenoxaprop were 56.9 and 1.5 days in the control and biochar-amended soils, respectively. Biochar restrained the formation and promoted the dissipation of fenoxaprop. Biological indicator earthworms (Eisenia fetida) were used in a 14-day acute toxicity test. Fenoxaprop-ethyl showed low toxicity to earthworms with LC50 value of 322.9 μg g⁻¹. Biochar amendment was non-toxic to earthworms and effectively reduced the toxicity. The results suggested that the application of biochar may reduce the risks of fenoxaprop-ethyl in the soil environment.
... The results indicate improved bulk density and increases in active carbon and potential nitrogen mineralisation compared with unamended soil (Sax et al., 2017). For these reasons, some authors have developed systems that obtain a compost-like biochar (Agegnehu et al., 2016) or work with mixed mature compost with biochar added to the soil (Agegnehu et al., 2016;Bielská et al., 2017). Bielská et al. (2017) showed that the joint use of compost and biochar was successful in the sorption of pyrene from contaminated soils and promoted the development of a model nematode. ...
... For these reasons, some authors have developed systems that obtain a compost-like biochar (Agegnehu et al., 2016) or work with mixed mature compost with biochar added to the soil (Agegnehu et al., 2016;Bielská et al., 2017). Bielská et al. (2017) showed that the joint use of compost and biochar was successful in the sorption of pyrene from contaminated soils and promoted the development of a model nematode. In some cases, biochar has been proposed as a co-substrate for the composting process itself of FW or agricultural residues (Khan et al., 2016;Vandecasteele et al., 2016). ...
This review analyses the main challenges of the process of food waste composting and examines the crucial aspects related to the quality of the produced compost. Although recent advances have been made in crucial aspects of the process, such composting microbiology, improvements are needed in process monitoring. Therefore, specific problems related to food waste composting, such as the presence of impurities, are thoroughly analysed in this study. In addition, environmental impacts related to food waste composting, such as emissions of greenhouse gases and odours, are discussed. Finally, the use of food waste compost in soil bioremediation is discussed in detail.
... Several studies have shown that soil DHA can be used as a sensitive indicator of PAH or heavy metal contamination Santos et al. 2011;Manzano et al. 2014;Araujo et al. 2015). Soil pyrene mitigation is influenced by soil microbial activity (Bielská et al. 2017). According to Moreno et al. (2011) and Tan et al. (2017), high Cd concentrations in soil inhibit soil dehydrogenase activity. ...
The environment in India is contaminated with polycyclic aromatic hydrocarbons (PAHs) due to the occurrence of large anthropogenic activities, i.e., fuel combustion, mineral roasting, and biomass burning. Hence, 13 toxic PAHs were detected: phenanthrene, anthracene, fluoranthene, pyrene, and benz(a) anthracene, ben-zo; (b) fluoranthene, benzo(k) fluoranthene, benzo(a) pyrene, benzo(ghi)perylene, dibenz (ah) anthracene, indeno1,2,3-(cd) pyrene, coronene and coronene in the environment (i.e., ambient particulate matter, road dust, sludge, and sewage) of the most industrialized area. Pollutants such as heavy metals and polycyclic aromatic hydrocarbons co-contaminate the soil and pose a significant hazard to the ecosystem because these pollutants are harmful to both humans and the environment. Phytoremediation is an economical plant-based natural approach for soil clean-up that has no negative impact on ecosystems. The aim of this study was to investigate the effects of pyrene (500 mg kg⁻¹), Zn (150 mg kg⁻¹), Pb (150 mg kg⁻¹), and Cd (150 mg kg⁻¹) alone and in combination on the phytoextraction efficiency of Medicago sativa growing in contaminated soil. Plant biomass, biochemical activities, translocation factors, accumulation of heavy metals, and pyrene removal were determined. After 60 days of planting, compared with those of the control plants, the growth parameters, biomass, and chlorophyll content of the M. sativa plants were significantly lower, and the reactive oxygen species activity, such as proline and polyphenol content and metallothionein protein content, was markedly greater in the pyrene and heavy metal-polluted soils. Furthermore, the combined toxicity of pyrene and all three metals on M. sativa growth and biochemical parameters was significantly greater than that of pyrene, Zn, Pb, or Cd alone, indicating the synergistic effect of pyrene and heavy metals on cytotoxicity. Pyrene stress increased Cd accumulation in M. sativa. After pyrene exposure alone or in combination with Zn-pyrene, a greater pyrene removal rate (85.5–81.44%) was observed than that in Pb-pyrene, Cd-pyrene, and Zn-Pb-Cd-pyrene polluted soils (62.78–71.27%), indicating that zinc can enhance the removal of pyrene from contaminated soil. The resulting hypotheses demonstrated that Medicago sativa can be used as a promising phytoremediation agent for co-contaminated soil.
... Toxicity of pollutants, such as Cd and cationic surfactants in freshwater sediments, could be better explained by pore water than by sediment concentrations (Höss et al. 2001b; Thomas et al. 2009). Moreover, pyrene toxicity in soils was well related to pore water concentrations (Bielská et al. 2017). Also in aqueous toxicity testing, chemicals bind to food bacteria, which reduces their freely dissolved concentrations (C free ) and causes a decreasing toxicity with increasing bacterial density . ...
Caenorhabditis elegans is used for assessing the toxicity of chemicals in aqueous medium. However, chemicals can absorb to the bacterial food, which reduces the freely dissolved concentrations of the tested compounds. Thus, based on total or nominal concentrations, toxicity is underestimated, resulting in misleading assumptions on toxicity mechanisms or comparisons to other test organisms. As the verification of freely dissolved exposure concentrations (Cfree) is challenging in small test systems, simple partitioning models might by a good option for estimating Cfree. Therefore, C. elegans was exposed to seven differently acting organic chemicals with varying hydrophobicities, thus also different affinities to bind to the food of C. elegans. Measured concentrations of the dissolved aqueous and the bacterial-bound fraction allowed the calculation of binding constants (Kb). Experimental Kb were comparable to literature data of hydrophobic chemicals and correlated well with their hydrophobicity, expressed as log KOW. The chronic toxicity of the various compounds on C. elegans' reproduction, based on their aqueous concentration, was weakly related to their log KOW. Toxicity expressed based on chemical activity and comparisons with a baseline toxicity model, nevertheless, suggested a narcotic mode of action for most hydrophobic compounds (except methylisothiazolinone and trichlorocarbanilide). Although revealing a similar toxicity ranking than Daphnia magna, C. elegans was less sensitive, probably due to its ability to reduce its internal concentrations by means of its very impermeable cuticle or by efficient detoxification mechanisms. It could be shown that measured aqueous concentrations in the nematode test system corresponded well with freely dissolved concentrations that were modeled using simple mass-balance models from nominal concentrations. This offers the possibility to estimate freely dissolved concentrations of chemicals from nominal concentrations, making routine testing of chemicals and their comparison to other species more accurate.
... These 16 spectra may well become a source of false identification, if tetramethyl pyrene is present in the analysed sample. At the same time, there are studies on the toxicity of pyrene [17], but the toxicity of its homologues was not investigated. If we take the extremely toxic 2,3,7,8-tetrachlorodibenzodioxine [18] as an example, there are no mass spectra of even a monomethyl derivative for it, and there are only two other substances with the same molecular formula. ...
Modern development vector of environmental monitoring leads to elaboration of analytical methods for qualitative and quantitative analysis of different ecotoxicants. Many studies face the lack of information on isomers and homologues of already studied compounds. This problem cannot always be solved experimentally due to the difficulty of separating or synthesizing certain compounds; the use of group theories of solutions will help partly; using them, solubility in water or partition coefficient between two immiscible solvents is calculated for ecotoxicants. These parameters are important for solving the analytical and ecological problems. The partition coefficient in the octanol – water system is associated with a possibility of accumulation of different compounds in living organisms; the partition coefficient in the hexane – acetonitrile system can be used in gas chromatographic analysis. Solubility in water is closely associated with accumulation of ecotoxicants in water bodies, as well as with their ability to be transferred. This paper presents the capabilities of the UNIFAC model for solving physicochemical problems using the example of calculating the properties of real ecotoxicants on the basis of the available thermodynamic data. All the obtained calculated values were compared with those determined experimentally. In the case of pyrene derivatives, solubility data were obtained for the first time using a correlation group model to calculate the heat of fusion and melting temperature.
... The behaviour of a biochar as amendment for contaminant removal depends on its properties and current state of aging/weathering (Semple et al., 2013). Biochar reduces PAHs extractability, bioaccessibility, bioavailability, and toxicity in soils and these effects increase with rise in biochar application rate (Bielska et al., 2017;Jimenez et al., 2018;Ogbonnaya et al., 2016). Biochar reduced water soluble fraction of phenanthrene hence indicating biochar as a suitable amendment to prevent PAHs leaching and bioaccessibility (Ogbonnaya et al., 2014;Jimenez et al., 2018). ...
Heavy metals (HMs) contamination raises the expression of antibiotic resistance (AR) in bacteria through co-selection. Biochar application in composting improves the effectiveness of composting and the quality of compost. This improvement includes the elimination and reduction of antibiotic resistant genes (ARGs). The use of biochar in contaminated soils reduces the bioaccessibility and bioavailability of the contaminants hence reducing the biological and environmental toxicity. This decrease in contaminant bioavailability reduces contaminants induced co-selection pressure. Conditions which favour reduction in HMs bioavailable fraction (BF) appear to favour reduction in ARGs in compost and soil. Biochar can prevent horizontal gene transfer (HGT) and can eliminate ARGs carried by mobile genetic elements (MGEs). This effect reduces maintenance and propagation of ARGs. Firmicutes, Proteobacteria, and Actinobacteria are the major bacteria phyla identified to be responsible for dissipation, maintenance, and propagation of ARGs. Biochar application rate at 2-10% is the best for the elimination of ARGs. This review provides insight into the usefulness of biochar in the prevention of co-selection and reduction of AR, including challenges of biochar application and future research prospects.
... Pyrene toxicity on C. elegans in Lufa 2.2 standard soil (EC50: 112 mg/kg dry soil) was lower than observed for other soil types. Bielská et al. (2017) reported EC50 values of 31 and 14 for C. elegans reproduction in two different soils spiked with pyrene. Although these soils had lower organic carbon contents (1.7 and 1.0% OC, respectively) than Lufa-soil (2.0% ...
Soils are among the most densely inhabited and biodiverse habitats on our planet, and many important soil ecosystem services depend on the health condition of the native soil fauna. Anthropogenic stress such as chemical pollution acting on the native soil fauna might jeopardize these functions. Laboratory microcosm tests are an appropriate tool for assessing the risk of chemicals on the native soil fauna and can be regarded as intermediate tier tests, bridging the gap between single species toxicity tests and field testing. Nematodes are one of the most abundant and divers soil invertebrates, and as such native nematode communities might be suitable for ecotoxicological assessments in laboratory microcosm set ups. In order to test such a small-scale (30 g soil) microcosm system, two different chemicals (zinc and pyrene) were assessed in various soil types for their effects on the respective native nematode communities. Various community parameters such as total nematode density, genus richness and genus composition, as well as trait-related indices (e.g. maturity index) were monitored over a period of 8–10 weeks. The response of the nematode communities strongly varied between soil types, and these differences were more pronounced for Zn than for pyrene. Interestingly, the structure of the respective native nematode communities was shown to play a larger role for explaining the varying toxic effects than soil properties governing the bioavailability of the spiked chemicals. We demonstrated that exposure of natural nematode communities in their original soil matrix to the metal zinc and to pyrene under climatically highly controlled conditions resulted in quantitatively and qualitatively distinct responses. Upon comparison of various community indices, the maturity index was shown to be the most sensitive toxicity endpoint for all tested soils and chemicals.
... Oxygen-containing functional groups are known to increase soil cation exchange capacity and contribute to the retention of heavy metals in weathered acidic soil (Uchimiya et al., 2011a). Aromatic structures can adsorb organic compounds via π-π interactions (Bielska et al., 2017), and determine the carbon sequestration ability of the biochar (McBeath et al., 2015). Mineral compounds released from biochars contribute to the neutralization of acidic soils (Dai et al., 2017), immobilization of heavy metals via surface precipitation and cation exchange (Uchimiya et al., 2011b;Fang et al., 2016), and act as an additional fertilizer to improve soil fertility (Ding et al., 2016). ...
To deeply assess the feasibility of sewage sludge-based biochars for use in soil applications, this review compared sewage sludge-based biochars (SSBBs) with lignocellulose-based biochars (LCBBs) in terms of their pyrolysis processes, various fractions and potential soil applications. Based on the reviewed literature, significant differences between the components of SSBB and LCBB result in different pyrolysis behavior. In terms of the fractions of biochars, obvious differences were confirmed to exist in the carbon content, surface functional groups, types of ash fractions and contents of potential toxic elements (PTEs). However, a clear influence of the feedstock on labile carbon and polycyclic aromatic hydrocarbons (PAHs) was not observed in the current research. These differences determined subsequent discrepancies in the soil application potential and corresponding mechanisms. The major challenges facing biochar application in soils and corresponding recommendations for future research were also addressed. LCBBs promote carbon sequestration, heavy metal retention and organic matter immobilization. The application of SSBBs is a promising approach to improve soil phosphorus fertility, immobilize heavy metals and provide available carbon sources for soil microbes to stimulate microbial biomass. The present review provides guidance information for selecting appropriate types of biochars to address targeted soil issues.
... BCs have also been effective in adsorbing dye Rhodamine B (RB) due to RB-BC electrostatic interactions and RB protonation at low pH (Qiu et al. 2009). Besides that, BC has been found to be effective in reducing the bioavailability of pyrene in soil pore water, hence, reduction of its toxicity in the soil (Bielská et al. 2017). Furthermore, BC is reported to be effective in sorbing methyl violet, oxytetracycline, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs), as well as in degradation of chlorobenzene (Zhang et al. 2018a). ...
Industries continuously emit xenobiotics into the environment, which increases risks of exposing humans and other biota to xenobiotics. Though various conventional and modern environmental remediation technologies are being employed, some of them are ineffective in removing xenobiotics, while others are costly and not feasible for large-scale utilization. Maize stover (MS) and rice husks (RH) are produced in abundance globally, which make them ideal and cost-effective feedstocks for large-scale biochar production for environmental remediation. Since either type of pristine MS and RH biochar may not be effective in removing some xenobiotics, the incorporation of modifiers into MS/RH biochars can help to form composite MS/RH biochar which in turn can better decontaminate water and soil. Thus, this review paper provides a comprehensive overview of the preparation, characterization, and environmental remediation using pristine and composite MS/RH biochar. Possible areas for composite MS/RH biochar applications and future perspectives of the technology in reducing xenobiotics are also proposed in this paper.
... This might be attributed to the increased nutrient supply [37], or the uncharacterised benefits related to the altered microbial community [53]. The increased biomass of carrot roots could possibly be attributed to the reduced toxicity of BDE-47 in soil, as found by [54,55] in response to biochar amendment. ...
... Wang et al., 2018). However, compared to unmodified soils or other blank controls, nematodes might avoid biochars because of toxins such as pyrene (Bielska et al., 2017), free radicals (Lieke et al., 2018), or even changes in water content and temperature. Therefore, the impact of biochar amendment on the behaviour of soil nematodes is unclear as are the phenotypic and/or reproductive changes that might occur along with their associated mechanisms. ...
Biochars have drawn wide attention as adsorbents, carbon sequesters and soil re-mediators. However, these substances are ambiguous regarding their effects on the motility, phenotypic changes and potential adaptative mechanisms of soil organisms. This study investigated how peanut shell biochar (PBC) affects the C. elegans model via a one-choice selection test and RNA-seq analysis. The results showed that C. elegans were able to select either PBC or a water control, and a clear preference for PBC was observed after 48 h of exposure, with the chemotaxis index (CI) reaching approximately 1.0. The nematode preferences for PBC vs sterile PBC/graphite were not significant, which demonstrated that initial microorganisms and appearances were not the reasons for the worms' selection, but the selection behaviour was instead determined by volatile odours. The treatments also showed that biochar amendment significantly decreased the body length, brood size and superoxide dismutase (SOD) activity of C. elegans to 960.20 ± 15.23 μm, 173.22 ± 4.56, 165.81 ± 3.82 U/mL SOD, respectively. Then, a possible molecular mechanism of PBC-induced developmental and reproductive effects on C. elegans was explored. Differential gene expression analysis was performed, and 1625 genes (1425 up- and 225 downregulated genes) were regulated in response to PBC treatment. The top 20 regulated genes were col genes (col-129; col-81; col-139; col-71), bli-6, perm-4 and his-24, which indicated that cuticle collagen synthesis, eggshell formation and/or heterochromatin in postembryonic growth may be disrupted following exposure to PBC. Therefore, our study suggested that quality standards be used to test nematode preferences and responses to biochar amendment, with the aim of safe application in soils, seedling substrates or fertilizers.
... Whatever raw materials were used (e.g., woody, miscanthus), the biochars significantly decreased the extractability of PAHs with three and four rings from soil in absence of ryegrass. Thus, biochars immobilized PAHs in soil, probably via sequestration processes, including sorption phenomena and a physical trap facilitated by the aromatic structure of biochars, their substantial porosity, their specific surface area, and their carbon content (Ogbonnaya et al. 2014(Ogbonnaya et al. , 2016Cao et al. 2016;Bielská et al. 2017;Song et al. 2017b). These results are consistent with those obtained in several studies in which the authors showed a decrease of extractable PAH concentrations after adding biochars made from wood, demolition wood waste, bamboo, corn straw, and wheat straw (Ogbonnaya et al. 2014(Ogbonnaya et al. , 2016Ni et al. 2017;Song et al. 2017b). ...
The present study experimented five biochars, one made from wood (400 °C, 12 h) and four made from miscanthus cultivated on contaminated soils (temperature 400/600 °C, duration 45/90 min). They were used as amendments at a 2% application rate on soil, cultivated or not cultivated with ryegrass, contaminated with (i) metals (Cd, Pb, and Zn), (ii) eight polycyclic aromatic hydrocarbons (PAHs), and (iii) a mix of metals and PAHs. The objectives were (i) to compare the effectiveness of the five biochars on soil parameters and pollutant availability and (ii) to determine the influence of soil multicontamination and ryegrass cultivation on biochar effectiveness. The results showed that biochar application did not necessarily lead to lower pollutant extractability and metal bioaccessibility. However, differences were highlighted between the biochars. The miscanthus biochars produced at 600 °C (BM600) showed higher effectiveness at decreasing metal extractability than the miscanthus biochars produced at 400 °C (BM400) due to its better sorption characteristics. In addition, ryegrass cultivation did not impact pollutant availability but modified metal bioaccessibility, especially for the soil amended with the BM600 and the woody biochar. Moreover, the presence of PAHs also negatively impacted the metal bioaccessibility in the soil amended with the BM600, and, on the contrary, positively impacted it in the soil amended with the BM400. Complementary studies are therefore necessary to understand the mechanisms involved, particularly in a context where soils requiring remediation operations are often multicontaminated and vegetated.
... Further, amendment of biochar improves physicochemical and biological characteristics of soil and makes it fertile by retaining water and water-soluble nutrients helping in the promotion of plant growth and development and reduction in the use of chemical fertilizers for the same processes Houben et al. 2013). Sometimes, it is used in combination with various chemical and organic fertilizers, activated carbon, compost, and manure to enhance the process (Bielská et al. 2017;Liang et al. 2017). Zea maize showed increased phytoremediation of PAHs and potentially toxic elements (PTEs) after amending the soil with maize and pine-derived biochar and commercialgrade activated carbon (Brennan et al. 2014). ...
Anthropogenic pollution caused by excessive use of chemicals, metals, radioactive substances, and organic pollutants has deteriorated quality of environmental assets, i.e., air, water, and soil. To restore the quality of all these essential systems, scientists and researchers are trying to stabilize contaminants in-situ rather than in in-vivo conditions. One of such effort is phytoremediation, which utilizes the application of green plants, herbs, and shrubs at contaminated sites to restrict the movement of pollutants and to decontaminate polluted sites. Application of various kinds of plants for bioremediation of polluted soils is an eco-friendly approach, with negligible effect over environment and also without disturbing the soil physicochemical properties. This technology also offers an opportunity to rejuvenate precious metals and utilize left biomass for the production of bioenergy. The present book chapter deals with different aspects of phytoremediation processes for remediation and recovery of contaminated soil and improving its efficiency with augmentation of different organic and inorganic amendments. Soil amendments can lessen up the bioavailability of contaminants in soils and decrease the risk of food chain contamination. These amendments include the application of biochar, vermicomposting, slow-release fertilizers, and nanoparticles to the soil to enhance the phytoremediation process. Role of these amendments on bioavailability of contaminants, their uptake, translocation, bioaccumulation, and its effect on growth and developments of plants has been thoroughly addressed in the present chapter. Further, different constraints like slow growth rate and effect of seasonal variations on development of plants have also been discussed.
... The previous work found that the appropriate ratio of biochar to compost in remediation of heavy metals ranged from 0.2 to 0.4 . Other researchers found that a ratio of 0.5 still showed good performances in the remediation of organic contaminants such as polycyclic aromatic hydrocarbons (Sigmund et al., 2018;Bielska et al., 2017). ...
Biochar and compost, two common amendments, were rarely conducted to investigate their combined influence on enzymatic activities and microbial communities in organic-polluted wetlands. This article described the effects of biochar/compost on degradation efficiency of sulfamethoxazole (SMX) and ecosystem responses in polluted wetland soil during the whole remediation process. 1% biochar (SB1) increased degradation efficiency of SMX by 0.067% ascribed to the increase of dehydrogenase and urease. 5% biochar (SB5) decreased degradation efficiency by 0.206% due to the decrease of enzymes especially for dehydrogenase. 2% compost (SC2), 1% biochar & 2% compost (SBC3), both 10% compost (SC10) and 5% biochar & 10% compost (SBC15) enhanced degradation efficiency by 0.033%, 0.015% and 0.222%, respectively, due to the increase of enzymes and biomass. The degradation efficiency was positively related to biomass and enzymatic activities. High-throughput sequencing demonstrated that HCGs (SB5, SC10, SBC15) improved the bacterial diversities but reduced richness through introducing more exogenous predominance strains and annihilated several inferior strains, while LCGs (SB1, SC2, SBC3) exhibited lower diversities but higher richness through enhanced the RAs of autochthonal preponderant species and maintained some inferior species. Additionally, HCGs raised the RAs of amino and lipid metabolism gene but lowered those of carbohydrate compared with LCGs.
... And, although waste is mentioned as a possible test item in the scope of the guideline, the test has never been validated for this purpose. However, the nematode toxicity test had already been used for assessing the toxicity of biochar mixed in soil (Bielská et al. 2017). Due to its short test duration (4 days) and miniaturized test design (multi-well plates), thus requiring low amounts of test item, the chronic toxicity test with C. elegans is valuable and cost-effective alternative to other invertebrate tests. ...
The ecotoxicological characterization of waste according to the European Waste List (HP14) is part of its hazard classification, which is based on 15 different hazardous properties and should include toxicity tests representing the aquatic and terrestrial compartment. Besides established soil toxicity tests with bacteria, plants, and earthworms, the standardized test with the nematode Caenorhabditis elegans (ISO 10872:2010) is suitable for testing soils and wastes, however, has never been validated for the purpose of waste toxicity assessment. Therefore, 23 different waste samples were tested for their toxicity on growth and reproduction of C. elegans to validate the suitability of ISO 10872 (ISO 2010) for assessing the ecotoxicological hazard of waste and to compare the results with those of other ecotoxicological test systems. C. elegans showed a comparable response to the waste samples as the earthworm avoidance test, however, with single samples where the nematodes indicated a higher toxicity than the E. fetida, thus, providing non-redundant information to the ecotoxicological hazard assessment of wastes. Also due to the short duration (4 days) and small-scale test set-up, the soil toxicity test with C. elegans turned out to be a valuable addition to already existing test batteries, for assessing the ecotoxicity of wastes in the soil compartment.
... This might be attributed to the increased nutrient supply [37], or the uncharacterised benefits related to the altered microbial community [53]. The increased biomass of carrot roots could possibly be attributed to the reduced toxicity of BDE-47 in soil, as found by [54,55] in response to biochar amendment. ...
Biochar application to soil is recognised for its capacity to immobilise pollutants (through sorption) while composted inputs can accelerate the biodegradation of organic pollutants. However, little is known about the influence of combined incorporation on plant uptake of organic pollutants. Therefore, we investigated the effects of maize straw-derived biochar (MSB), compost derived from maize straw and pig manure (SMC), and their combination (MSB-SMC) as soil amendments on bioavailability of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and carrot (Daucus carota L.) uptake in a horticultural soil. We found that biochar alone performed well in reducing BDE-47 bioavailability, but was less effective at degrading the pollutant. Conversely, addition of compost stimulated BDE-47 biodegradation. MSB-SMC enhanced BDE-47 biodegradation in soil, reduced contamination of carrot roots, and caused significant reductions in soil extractable BDE-47. The combination of contrasting approaches to remediation thus resulted in the most favorable outcome for a contaminated soil: immobilisation of contaminant from vegetable crops (via biochar) with simultaneous bioremediation of the growing medium. These findings point towards an effective strategy for reducing plant uptake of PDBEs through the combined use of biochar and compost as soil amendment – reducing mobility and facilitating degradation of the accessible contaminant fractions.
... In addition, it is reasonable to assume that the interaction among components in bio-organic fertilizer is important for the removal of contaminants in the soil. Bielska et al. (2017) reported that the combination of biochar and compost amended pyrene-spiked soil and reduced pyrene porewater concentrations effectively. Moreover, the interaction of CMOF and biochar may affect the abundance of atrazine-degrading bacteria and its surrounding microorganisms, thus affecting the removal of atrazine in the soil. ...
The accumulation of atrazine in farmland is prone to cause phytotoxicity to kinds of sensitive crops, such as soybean. In addition, some kinds of agricultural solid wastes have long been considered as the important non-point pollution source. The aim of this experiment was to investigate the feasibility of removing atrazine from soil and alleviating the stress of atrazine on the growth of soybean by application a novel bio-organic fertilizer developed by agricultural solid wastes, such as cow manure organic fertilizer, biochar and poly-(γ-glutamic acid), as well as an atrazine-degrading strain Arthrobacter sp. DNS10. Sixteen potential bio-organic fertilizer formulations were designed by D-optimal mixture design of Design Expert software and atrazine-removal ability was selected to single out the optimal formulation. As a result, the optimal formulation of bio-organic fertilizer (named as DNBF10) was produced by the cow manure organic fertilizer 76.20%, biochar 4.46%, poly-(γ-glutamic acid) 8.63% (m/m) and the number of Arthrobacter sp. DNS10 with 0.91 × 10⁸ CFU/g. The atrazine removal percentage of DNBF10 for the atrazine in soil with the initial atrazine concentration 15.26 ± 0.49 mg/kg was 95.05% after 10 days’ application with DNBF10 at the adding dosage of 5 mg/kg (relative to the dry weight of the soil). Furthermore, pot experiment results suggest that the growth of soybean seedlings in the soil (initial atrazine was 8.14 ± 0.16 mg/kg) that adding both of DNBF10 (25%) and chemical fertilizer (75%) were better than those of the treatment only adding chemical fertilizer (100%) under the same nutrient addition level. All the results indicate that the application of DNBF10 was a new alternative to reuse the typical agricultural solid wastes, as well as to reduce the harm caused by residual atrazine to soybean.
... PAH biodegradation by microbes would be influenced due to the decline of microbial activity. However, addition of compost to soil could improve soil structure by adding structural forming materials to enhance emission of PAH degradation product, and decrease the porewater concentration reflecting the bioavailability and toxicity of PAHs (Bielska et al. 2017;Wloka et al. 2017). These benefits of addition compost boost the activity of microorganisms with the results of DHA increment. ...
In this study, greenhouse experiments were conducted under the condition of different amendment ratios and planting tall fescue (Festuca arundinacea). The amendment ratios of sewage sludge or sludge compost to soil were of 0, 10, 25, and 50% (w/w). The removal rates of PAH, catalase, and dehydrogenase activities of amended soil and accumulation of PAHs by vegetation were detected to investigate the differences of PAH dissipation in sludge-amended and compost-amended soils. The initial PAH concentrations in three amended soils increased with the more addition of sludge or compost. After 126-day experiment, maximum PAH removal rates were observed in sludge-amended and compost-amended soils with PAH concentration of about 200 μg kg⁻¹. And the removal of PAHs showed better efficiencies in compost soil rather than in sludge soil. The more catalase activity and dehydrogenase activity of soil were obtained, respectively, in sludge soil and compost soil. The results indicated that the mechanism of PAH dissipation in two types of amended soils were different. The abundant amount of microorganism dominated PAH dissipation in sludge soils, and PAHs dissipated mainly caused of intense activity of microorganism in compost soils. In addition, PAH accumulation in tall fescue suggested that the transference approach of PAHs was from soil to the roots, and then accumulated in the shoots of tall fescue. It was prone to store up more PAHs in vegetation in the condition of high molar weight of PAHs, more biomass of vegetation, and heavy PAH concentration in soil.
... The positive effect of compost addition on the total number of culturable microorganisms has been previously observed in soil contaminated with diesel oil (Gandolfi et al., 2010) and heavy crude oil (Trejo-Hernández et al., 2007). Similar findings showed that bioavailable and readily available concentrations may be reduced when applying compost amendment without hindering biodegradation (Bielská et al., 2017;Marchal et al., 2013). The beneficial effect observed for compost-amended soil can be attributed to (1) the increase in nutrients content, (2) the enrichment of the microbial community, (3) a positive effect of pH adjustment (slightly alkaline pH of compost) towards a more neutral pH value (Kästner and Miltner, 2016). ...
A six-month laboratory scale study was carried out to investigate the effect of biochar and compost amendments on complex chemical mixtures of tar, heavy metals and metalloids in two genuine contaminated soils. An integrated approach, where organic and inorganic contaminants bioavailability and distribution changes, along with a range of microbiological indicators and ecotoxicological bioassays, was used to provide multiple lines of evidence to support the risk characterisation and assess the remediation end-point. Both compost and biochar amendment (p = 0.005) as well as incubation time (p = 0.001) significantly affected the total and bioavailable concentrations of the total petroleum hydrocarbons (TPH) in the two soils. Specifically, TPH concentration decreased by 46% and 30% in Soil 1 and Soil 2 amended with compost. These decreases were accompanied by a reduction of 78% (Soil 1) and 6% (Soil 2) of the bioavailable hydrocarbons and the most significant decrease was observed for the medium to long chain aliphatic compounds (EC16-35) and medium molecular weight aromatic compounds (EC16-21). Compost amendment enhanced the degradation of both the aliphatic and aromatic fractions in the two soils, while biochar contributed to lock the hydrocarbons in the contaminated soils. Neither compost nor biochar affected the distribution and behaviour of the heavy metals (HM) and metalloids in the different soil phases, suggesting that the co-presence of heavy metals and metalloids posed a low risk. Strong negative correlations were observed between the bioavailable hydrocarbon fractions and the ecotoxicological assays suggesting that when bioavailable concentrations decreased, the toxicity also decreased. This study showed that adopting a combined diagnostic approach can significantly help to identify optimal remediation strategies and contribute to change the over-conservative nature of the current risk assessments thus reducing the costs associated with remediation endpoint.
... The spiked soil was amended with biochar (5% v/v) and compost (5% v/v). The concentrations of amendments (biochar and compost) were selected on the basis of already published literature (Bielská et al., 2017, Zhang et al., 2016a. Green garden waste biochar was obtained from AIT Austrian Institute of Technology, Tulln, Austria. ...
Petroleum hydrocarbons are extensively utilized in petrochemical industries and cause soil deterioration during exploration, transportation, refining and making petroleum products. We hypothesized that the combined use of compost, biochar and bacterial consortia as soil amendments may enhance the rhizoremediation potential of ryegrass by strengthening the plant rhizospheric effect for efficient total petroleum hydrocarbon removal. The present study focused on phytoremediation of hydrocarbons in spiked contaminated soil amended with biochar (5% v/v), and compost (5% v/v). Spiked soil was inoculated with consortia of four hydrocarbon degrading bacterial strains (Pseudomonas poae, Actinobacter bouvetii, Stenotrophomonas rhizophila and Pseudomonas rhizosphaerae). The spiked soil was prepared by spiking agricultural soil with 3.4% (w/w) of crude oil. Italian ryegrass (60 seeds pot−1) were sown and plants were harvested after 75 days.
The highest hydrocarbon removal (85%) was observed in spiked soil amended with compost, biochar and consortia. Bacterial inoculation with biochar and compost showed significantly higher hydrocarbon degradation as compared to all other treatments. Highest TPHs degrading bacteria (5.74 × 107 cells g−1 of soil) were observed in rhizosphere of spiked soil amended with compost, biochar and consortia. The organic amendments improved plant growth and bacterial count in rhizosphere which resulted in higher removal of hydrocarbons. We concluded that plant-microbe interactions together with the organic soil amendments offer an emerging trend for remediation of hydrocarbons. Rhizoremediation is a green solution to overcome the quandary of total petroleum hydrocarbon contamination in soil.
... The spiked soil was amended with biochar (5% v/v) and compost (5% v/v). The concentrations of amendments (biochar and compost) were selected on the basis of already published literature (Bielská et al., 2017, Zhang et al., 2016a. Green garden waste biochar was obtained from AIT Austrian Institute of Technology, Tulln, Austria. ...
Petroleum hydrocarbons are extensively utilized in petrochemical industries and cause soil deterioration during exploration, transportation, refining and making petroleum products. We hypothesized that the combined use of compost, biochar and bacterial consortia as soil amendments may enhance the rhizoremediation potential of ryegrass by strengthening the plant rhizospheric effect for efficient TPH removal. The present study focused on phytoremediation of hydrocarbons in spiked contaminated soil amended with biochar (5% v/v), and compost (5% v/v). Spiked soil was inoculated with consortia of four hydrocarbon degrading bacterial strains (Pseudomonas poae, Actinobacter bouvetii, Stenotrophomonas rhizophila and Pseudomonas rhizosphaerae). The spiked soil was prepared by spiking agricultural soil with 3.4% (w/w) of crude oil. Italian ryegrass seeds (60/pot) were sown and plants were harvested after 75 days.
The highest hydrocarbon removal (85%) was observed in spiked soil amended with compost, biochar and consortia. Bacterial inoculation with biochar and compost showed significantly higher hydrocarbon degradation as compared to all other treatments. Highest TPH degrading bacteria (5.74×107 cells g-1 of soil) were observed in rhizosphere of spiked soil amended with compost, biochar and consortia. The organic amendments improved plant growth and bacterial count in rhizosphere which resulted in higher removal of hydrocarbons. We concluded that plant-microbes interactions together with the organic soil amendments offer an emerging trend for remediation of hydrocarbons. Rhizoremediation is a green solution to overcome the quandary of TPH contamination in soil.
... Biochar, the engineered form of char, has recently attracted attention in the agro-environmental community for its promising beneficial effects as a soil amendment (Godlewska et al., 2017) for improving soil quality (Laird, 2008;Basso et al., 2012;Lehmann and Joseph, 2015), increasing crop productivity (Jeffery et al., 2011), suppressing nitrous oxide (an important greenhouse gas) emissions (Lehmann, 2007b;Woolf et al., 2010), and retaining metal (Cao et al., 2009;Uchimiya et al., 2012;Qian et al., 2013) and organic contaminants (Spokas et al., 2009;Graber et al., 2012;Graber and Kookana, 2015;Kupryianchyk et al., 2016;Kah et al., 2017;Stefaniuk et al., 2017;Zhu et al., 2017). Biochar is also believed to be a sustainable means of carbon sequestration (Woolf et al., 2010;Lehmann and Joseph, 2015). ...
In this study, we systematically investigated the effects of thermal air oxidation on the properties of biomass-derived black carbon (BC) made at carbonization temperatures (HTTs) of 300–700 °C. BC produced by including air in the carbonization step was found to have a low surface area and underdeveloped pore structure. Substantial changes of BC were observed after post-pyrolysis thermal air oxidation (PPAO). Well-carbonized BC samples made anoxically at relatively high HTTs (600 and 700 °C) showed, after PPAO, significant increases in N2 BET surface area (SA) (up to 700 times), porosity (< 60 Å) (up to 95 times), and adsorptivity (up to 120 times) of neutral organic species including two triazine herbicides and one natural estrogen. Partially carbonized BC made at a lower HTT (300 or 400 °C) showed moderate increases in these properties after PPAO, but a large increase in the intensity of Fourier transform infrared spectroscopy bands corresponding to various oxygen-containing functional groups. Well-carbonized BC samples, on the other hand, were deficient in surface oxygen functionality even after the PPAO treatment. Adsorption of the test organic compounds on BC generally trended with BET SA when it was less than 300 m2/g, but BET SA was poorly predictive of adsorption when it was greater than 300 m2/g. Overall, our results suggest that thermal reactions between molecular oxygen and BC 1) increase surface oxygen functionality more effectively for low-HTT than for high-HTT BC samples; 2) increase SA and porosity (< 60 Å) especially for high-HTT BC samples; and 3) create new adsorption sites and/or relieve steric restriction of organic molecules to micropores, thereby enhancing the adsorptivity of BC. These results will prove useful not only for understanding the fate of environmental BC but also in devising strategies for improving the practical performance of the engineered form of BC (i.e., biochar).
As a representative variety of diamide insecticides, cyantraniliprole has broad application prospects. In this study, the fate and risk of cyantraniliprole and its main metabolite J9Z38 in a water-sediment system were investigated. The present result showed that more J9Z38 was adsorbed in the sediment at the end of exposure. However, the bioaccumulation capacity of cyantraniliprole in zebrafish was higher than that of J9Z38. Cyantraniliprole had stronger influence on the antioxidant system and detoxification system of zebrafish than J9Z38. Moreover, cyantraniliprole induced more significant oxidative stress effect and more differentially expressed genes (DEGs) in zebrafish. Cyantraniliprole had significantly influence on the expression of RyR-receptor-related genes, which was confirmed by resolving their binding modes with key receptor proteins using AlphaFold2 and molecular docking techniques. In the sediment, both cyantraniliprole and J9Z38 had inhibitory effects on microbial community structure diversity and metabolic function, especially cyantraniliprole. The methane metabolism pathway, mediated by methanogens such as Methanolinea, Methanoregula, and Methanosaeta, may be the main pathway of degradation of cyantraniliprole and J9Z38 in sediments. The present results demonstrated that metabolism can reduce the environmental risk of cyantraniliprole in water-sediment system to a certain extent.
Environmental pollution caused by polycyclic aromatic hydrocarbons (PAHs) jeopardizes nature. PAHs are the most toxic, mutagenic, and carcinogenic pollutants and their cleanup is important for the environment. In the current research, to assess and evaluate three remediation strategies for pyrene removal from the soil, a pot experiment was performed: (a) bioremediation with Pseudomonas aeruginosa and Aspergillus oryzae, (b) phytoremediation with sunflower (Helianthus annuus) and alfalfa (Medicago sativa L.) and (c) microbial-assisted phytoremediation for the treatment of pyrene (700 mg kg−1). Results depict that P. aeruginosa significantly promoted the growth and tolerance of taken plants and reduced pyrene concentration in soil. Compared with those planted in pyrene-contaminated soil without inoculation. The highest percentage of pyrene removal was observed in P. aeruginosa inoculated alfalfa (91%), alfalfa inoculated with A. oryzae (83.96%), and without inoculation (78.20%). Moreover, alfalfa planted in P. aeruginosa augmented soil had the highest dehydrogenase activity (37.83 μg TPF g−1 soil h−1), and fluorescein diacetate hydrolysis (91.67 μg fluorescein g−1 dry soil). DHA and FDA are the indicators of bioaugmentation influence on the indigenous microbial activity of contaminated soil. As a result of the findings, the rhizospheric association of plants and microbes is beneficial for pyrene removal. Therefore, P. aeruginosa-assisted phytodegradation might be a more successful remediation technique for pyrene-contaminated soil than bioremediation and phytodegradation solely.
Interactive climate factors, the industrial revolution, excessive fertilizer use, pesticides, wastewater use in agriculture, landfill leachates, and mine tailings cause land degradation and reduce crop production worldwide. Biochar can mitigate global climate change, reduce soil degradation, drought, and waterlogging effects, and increase crop production. It can also reduce the bioavailability and phytotoxicity of pollutants in contaminated soils via the mobilization of inorganic and/or organic contaminants, commonly through surface complexation, electrostatic attraction, ion exchange, and co-precipitation. When biochar is applied to soil, it typically neutralizes soil acidity and enhances soil aeration, water holding capacity, cation exchange capacity, and microbial activity, and therefore, it was employed to ameliorate crop abiotic/biotic stress. This review discusses the association of biochar with poor soil condition (salinity, drought, flooding and heavy metal stress) and their interactive effect to improve plant physiological performance and biomass production. Biochar applied with other stimulants like compost, humic acid, phytohormones, microbes and nanoparticles can surprisingly enhance plant farming, cultivation practices and plant eco-physiological responses in saline, waterlogged and dried areas with economic sustainability. Overall, biochar can provide an exciting and promising component, especially in nutrient-poor degraded soils for the improvement of plant cultivation and crop production worldwide taking it a step closer to successful commercialization.
Biochar has substantial potential as a globally significant negative emissions technology (NET) provided that it can be deployed economically at a sufficiently large scale without introducing unintended negative impacts. The generation of polyaromatic hydrocarbons (PAHs) during the production of biochars has been identified as a potential risk. A commonly applied risk management and certification mechanism is to set an upper limit on the total PAH loading of the produced biochar. However, this simple metric does not take into account the strong affinity for biochar to bind PAHs, which can significantly reduce their bioavailablity and associated potential risks to health and the environment. Nor does reflect the fact that not all PAHs are the same, and that the distribution of more and less toxic species within the total is influenced by a number of feedstock and production factors.
The capacity for biochar to adsorb potential toxins, not only PAHs, but also heavy metals and other organic pollutants from contaminated soils and aqueous media is an important and affordable mechanism to help reduce the uptake of such pollutants and their associated risks to health. Elevated concentrations of PAHs are often to be found in soils located in the vicinity of roads, heavy industries and crop-burning activities. The addition of suitably prepared biochar in such situations can result in a net reduction in bioavailable PAHs. Whilst the imposition of tight constraints is justifiable for certain applications, such as when used as a ruminant feed supplement, adherence to excessively tight constraints in general may unintentionally inhibit the generation of biochar by more affordable processes that would otherwise be sufficient to deliver net environmentally positive benefits, local and global. By managing overall risk on a more class-by-class basis, the potential for large-scale deployment of biochar as a NET may be realised effectively and safely.
Modified composite biochar offers a cost-effective solution for the remediation of contaminated sediments; however, few studies have evaluated the effects of modified composite biochar amendment on the ecotoxicity of contaminated sediment based on benthic macroinvertebrates. A 21-day sediment toxicity test was conducted using the freshwater snail Bellamya aeruginosa to examine the intrinsic ecotoxicity of a novel KOH-modified composite biochar (KOH-CBC) and its efficacy for reducing the bioavailability, uptake, and ecotoxicity of perfluorooctanoic acid (PFOA). It was found that KOH-CBC is toxic to B. aeruginosa, which may be attributed to its high polycyclic aromatic hydrocarbons (PAHs) content and alkalinity. The addition of KOH-CBC to PFOA-contaminated sediments can markedly reduce the bioavailability and uptake of PFOA by more than 90% and 50%, respectively, and subsequently alleviate the toxicity of PFOA to B. aeruginosa by at least 30%. Increasing the KOH-CBC dosage is not beneficial for further mitigating the toxicity of PFOA-contaminated sediments. Our findings imply that KOH-CBC is a promising sorbent for the in-situ remediation of PFOA-contaminated sediments. Application of acidified KOH-CBC at a dosage of approximately 1–3% will be sufficient to control the ecotoxicity of PFOA; however, its long-term environmental effects should be further validated.
Pyrene, a four-ring PAHs, is a typical pollutant in coking wastewater, which is difficult to biodegrade in the conventional biological wastewater treatment processes. Biodegradation of pyrene coupled with denitrification process is an effective approach for treating coking wastewater due to simultaneous removal of toxic organic pollutants and nitrate. In this study, a novel strain capable of degrading pyrene was isolated from the activated sludge of a local coking wastewater treatment plant and identified to be Casterllaniella sp. based on 16S rRNA gene sequence analysis. It can degrade pyrene under denitrifying condition. The degradation efficiency of pyrene reached 97.2% when pyrene concentration was 100 mg L⁻¹. According to the analysis of electron transformation process, about 50% of pyrene was degraded using nitrate as electron acceptor. During pyrene degradation process, almost no intermediate products were detected by GC-MS with the detection limit of 0.1 ng L⁻¹ perhaps due to the complete degradation of pyrene. The SDS-PAGE analysis showed that the proportion of 6 proteins increased during pyrene degradation, and 4 proteins could be considered as enzymes involved in pyrene degradation. The analysis of intermediate products and proteins suggested that pyrene degradation under anoxic condition by Castellaniella sp. Pyr2 was different from other aerobic pathways. Furthermore, this strain has potential for the practical application of simultaneous removal of pyrene and nitrate from coking wastewater.
Single crystal X-ray structurally characterized azo-uracil derivative (L) is explored for selective detection of pyrene via aggregation induced emission (AIE) with 99-fold fluorescence enhancement. In presence of pyrene, non-fluorescent L...
Isotope dilution techniques (IDT) and sequential extraction procedures (SEPs) were compared to apprehend the differences between two techniques in determining metal exchangeability and vulnerability to pollute the urban groundwater. For this purpose, soil (n = 2), “soakaway” sediment deposited in the artificial infiltration facilities (AIF) (n = 4), and road dust (n = 2) were sampled from Tokyo metropolitan. Sorption coefficients of four metals (Cu, Zn, Cd and Pb) were assessed through isotopic exchangeability (E-value) and potential mobile pool i.e. addition of exchangeable, reducible and oxidizable fraction obtained by Community Bureau of Reference (BCR)-procedures. The E-value for the three samples were found smaller than the potential mobile pool but were higher than BCR-exchangeable fractions. The use of strong extractants are likely to play an active role in the disagreement between SEPs and IDT. IDT accounts for the isotopic exchangeability while BCR provides information of vulnerability of metals associated with different fractions that can leach under different environmental conditions. Sorption coefficients measured in soakaway sediment was found comparable to soil thus likely to retain metals. However, as variability in environmental conditions is likely to affect Kd, the soakaway sediment may become an active metal source in future rather than acting as the permanent sink. The study concludes that there is the possibility of errors while predicting metal vulnerability to groundwater with both techniques and thus a model compliance integrating the virtue of both techniques will be a way forward pertaining to evaluation the environmental safety from AIF.
Pyrene is a fluorescent polycyclic aromatic hydrocarbon that can be volatilised under mild conditions. When fumed, pyrene is rapidly absorbed into the sebaceous residues of fingermarks, enabling their fluorescent visualisation upon excitation with ultraviolet radiation. This new means of fluorescent fingermark detection is more sensitive than the non-fluorescent iodine fuming approach for nonporous surfaces. This is demonstrated here in a phase 1 study using split-print comparisons on metal and glass surfaces. Pyrene-treated fingermarks also retain the volatile fluorophore for comparably long time periods relative to iodine fuming (in the order of hours). The phase 1 study comprised four donors, and 80 natural fingermarks that were grouped into two time periods; aged 24h and 1 week. Iodine fuming was chosen as a reference to showcase the effectiveness of pyrene given it is the most closely-related chemical fuming method in routine use. This study demonstrates that pyrene fuming increases the quantity and quality of fingermark visualisations relative to iodine fuming, and is free of many of the latter method's drawbacks. Preliminary results shown here also show the effectiveness of pyrene fuming on highly patterned surfaces, and its compatibility with the use of gelatine lifters. Pyrene fuming is thus easy to effect, low-cost, and shows great promise as a new means of visualising fingermarks on non-porous surfaces.
Since the introduction of standardized nematode toxicity assays by the American Society for Testing and Materials (ASTM) and International Organization for Standardization (ISO), many studies have reported their use. Given that the currently used standardized nematode toxicity assays have certain limitations, in this study, we examined the use of a novel nematode offspring counting assay for evaluating soil ecotoxicity based on a previous soil-agar isolation method used to recover live adult nematodes. In this new assay, adult Caenorhabditis elegans were exposed to soil using a standardized toxicity assay procedure, and the resulting offspring in test soils attracted by a microbial food source in agar plates were counted. This method differs from previously used assays in terms of its endpoint, namely, the number of nematode offspring. The applicability of the bioassay was demonstrated using metal-spiked soils, which revealed metal concentration-dependent responses, and with 36 field soil samples characterized by different physicochemical properties and containing various metals. Principal component analysis revealed that texture fraction (clay, sand, and silt) and electrical conductivity values were the main factors influencing the nematode offspring counting assay, and these findings warrant further investigation. The nematode offspring counting assay is a rapid and simple process that can provide multi-directional toxicity assessment when used in conjunction with other standard methods.
Recycling the biodegradable waste by composting represents a sustainable solution for developing new ecological compost-type substrates, useful both as biofertilizers and as sorbents for the removal of heavy metals from wastewaters. By this paper we aim to present an overview of our studies related to using composted biomass from biodegradable wastes, as viable solution for biofertilizers or sorbents for heavy metals removal from the environmental. The novelty of our studies consists of the new materials that were prepared by composting together different biomass wastes. Aerobic fermentation was used to obtain sixteen different composts from vegetables waste, sewage sludge, beech sawdust and beech ash, in different mixing ratio, and the composting process was monitored. Based on their composition, three of these mature and stable composts were selected, while their capacity as nutrients and suitability as bio-fertilizers were analyzed in terms of C/N ratio, germination tests. Furthermore, one of these composts was also demonstrated to be suitable as low-costs sorbent, specifically to remove heavy metals from polluted waters. For this application the topography and morphology of compost substrates were determined, before and after sorption of metal cations. The sorption parameters (contact time, ratio of wastewater volume: sorbent compost mass) were optimized. Both, kinetic and thermodynamic sorption mechanisms were discussed and the results were further correlated with the structural properties of the compost substrate. The advantaged of biodegradation wastes by composting different raw biomaterials for preparation of ecological soil fertilizers and sorbents to remove heavy metals from contaminated waters, as low cost and environmental friendly solutions were also discussed.
Compost or composting has been widely investigated under the background of heavy metal pollution of agricultural soils and rapid growth of organic wastes. Compost is rich in nutrients, humic matter, and microorganisms; it may be added to agricultural soil as a fertilizer to improve soil fertility and promote the growth of crops and microorganisms, and as a soil amendment to relieve heavy metal pollution. However, the effectiveness and security of compost application in agricultural soil continue to generate concern. In this review, the efficacy and mechanisms of compost remediation technologies for heavy metal-contaminated agricultural soil are presented. Poor quality, unsuitability for multiple heavy metal-contaminated soils, and potential long-term risks are the main limitations of the effectiveness and security of compost application to soils. Therefore, improving the quality of the compost, adding amendments, or combining with phytoremediation may be considered when adopting compost to remediate polluted agricultural soil. In addition, we propose several approaches to optimize these strategies and render the remediation of heavy metal-contaminated agricultural soil using compost safer and more effective. The findings of this review will help support the large-scale application of compost in agriculture in the future.
In chronic toxicity tests with Caenorhabditis elegans, it is required to feed with bacteria, which reduce the freely dissolved concentration (Cfree) of hydrophobic organic chemicals (HOCs), leading to poorly defined exposure with conventional dosing procedures. We examined the efficacy of passive dosing of polycyclic aromatic hydrocarbons (PAHs) using silicone O-rings to control exposure during C. elegans toxicity testing, and compared the results to those obtained with solvent spiking. Solid-phase microextraction and liquid-liquid extraction were used to measure Cfree and the chemical dose taken up via ingestion. During toxicity testing, Cfree decreased by up to 89% after solvent spiking but remained constant with passive dosing. This led to a higher apparent toxicity on C. elegans exposed by passive dosing than by solvent spiking. With increasing bacterial cell densities, Cfree of solvent spiked PAHs decreased while maintained constant with passive dosing. This resulted in lower apparent toxicity under solvent spiking, but an increased apparent toxicity with passive dosing, probably as a result of the higher chemical uptake rate via food (CUfood). Our results demonstrate the utility of passive dosing to control Cfree in routine chronic toxicity testing of HOCs. Moreover, both chemical uptake from water or via food ingestion can be controlled, thus enabling to discriminate different uptake routes in chronic toxicity studies.
Purpose
Nutrient deficiency and salt stress (sodium, Na+) strongly limited the productivity of the degraded coastal soils in the Yellow River Delta. Biochar-based functional materials have been considered as a promising amendment to solving the problem of global soil security (e.g., erosion, fertility loss, acidification, and salinization). Therefore, this study aimed to explore the potential of using a biochar-compost amendment (BCA) to improve the coastal soil properties and productivity.
Materials and methods
The BCA was produced from composting of biochar and additives including seafood shell powder, peanut shell, commercial humate, and inorganic nutrients. Two halophytes, sesbania (Sesbania canabina (Retz.) Pers) and seashore mallow (Kosteletzkya virginica), were chosen as the tested plants in a 52-day pot experiment. BCA was added as the rates of 0, 1.5, 5, and 10 % (w/w). At the end of the incubation, the shoot height, biomass, and root morphological parameters including length, tips, and surface area were measured, as well as the properties (e.g., soil organic matter (SOM) content and cation exchange capacity (CEC)) of the rhizosphere and non-rhizosphere soils.
Results and discussion
The BCA application at 1.5 % enhanced the growth of sesbania and seashore mallow and increased their total biomass by 309 and 70.8 %, respectively, while significantly inhibited both the halophyte growths at 10 %. Similarly, both the halophyte root morphologies (e.g., length and tips) significantly increased by BCA addition at 1.5 %. The promoting growth of the both halophytes could be resulted from the improvement of soil properties such as the increased SOM and CEC, the decreased amount of the exchangeable sodium (Ex-Na) and exchangeable sodium percentage (ESP), and the rhizosphere effect (e.g., decreased soil pH). The higher rate of BCA addition (e.g., 10 %) sharply increased soil salinity, responsible for the inhibition of both the halophyte growths. Although BCA addition may directly supply much nitrogen (N) for the soils, N bioavailability for both halophytes was not largely improved.
Conclusions
The short-term laboratory pot experiments revealed that producing the biochar-compost with desired properties (e.g., BCA) could be a feasible alternative to remediate the degraded coastal soil in the Yellow River Delta. Moreover, the addition of BCA should be kept at an optimal level, which may produce expected positive results. Our results will be helpful for supporting the strategy of designing right biochar-compost for the right soil.
Biochar (BC) application to soil suppresses emission of nitrous-(N 2 O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indo-nesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N 2 O and N 2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N 2 O and NO and increased N 2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N 2 O and NO suppression was dose-dependent and increased with the alkaliz-ing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N 2 O and NO net production. Just like untreated BCs, NaOH reduced net production of N 2 O and NO while increasing that of N 2. This confirms the importance of altered soil pH for denitrifica-tion product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.
This investigation examines nitrous oxide (N2O) fluxes from soil with simultaneous amendments of anaerobic digestates and biochar. The main source of anthropogenic emissions of N2O is agriculture and in particular, manure and slurry application to fields. Anaerobic digestates are increasingly used as a fertiliser and interest is growing in their potential as sources of N2O via nitrification and denitrification. Biochar is a stable product of pyrolysis and may affect soil properties such as cation exchange capacity and water holding capacity. Whilst work has been conducted on the effects of biochar amendment on N2O emissions in soils fertilised with mineral fertilisers and raw animal manures, little work to date has focused on the effects of biochar on nitrogen transformations within soil amended with anaerobic digestates. The aim of the current investigation was to quantify the effects of biochar application on ammonification, nitrification and N2O fluxes within soil amended with three anaerobic digestates derived from different feedstocks. A factorial experiment was undertaken in which a sandy loam soil (Dunnington Heath series) was either left untreated, or amended with three different anaerobic digestates and one of three biochar treatments; 0%, 1% or 3%. Nitrous oxide emissions were greatest from soil amended with anaerobic digestate originating from a maize feedstock. Biochar amendment reduced N2O emissions from all treatments, with the greatest effect observed in treatments with maximum emissions. The degree of N2O production and efficacy of biochar amelioration of gas emissions is discussed in context of soil microbial biomass and soil available carbon.
The application of pig manure to a tillage soil can result in pollution of surface and groundwater bodies.
Countries in the European Union are required to comply with the Water Framework Directive, which
states that all countries should attain at least “good status” surface and ground water quality by 2015.
Amendment of soil with biochar has previously been shown to reduce nutrient leaching and improve soil
properties. The objectives of this laboratory study were to investigate if the application of two types of biochar at
a rate of 18 t ha−1 (a) reduced leaching of carbon (C), nitrogen (N) and phosphorus (P) from a low P Index
tillage soil amended with pig manure and (b) affected the soil properties before and after pig manure application. Three treatments were examined as follows: (a) non-amended soil (the study control), (b) soil mixed with biochar from the separated solid fraction of anaerobically digested pig manure, and (c) of soil mixed with biochar from Sitka Spruce. Columns, filled with sieved soil (<2 mm) and biochar (<2 mm), were incubated for 30 weeks at 10 °C and 75%relative humidity and leached with 160 mL distilled water per week. Pig manure, equivalent to 170 kg N ha−1 and 36 kg P ha−1, was applied to half of the columns in each treatment after 10 weeks of incubation. Amendment with pig manure biochar increased the Morgan’s P content of the soil, while leaching of P and C also increased, indicating the unsuitability of pig manure biochar as an amendment to soils which may be used as pig manure spreadlands. However, the addition of wood biochar increased soil water, C and organic matter contents, while reducing nitrate and organic C leaching. The addition of wood-derived biochar to tillage soil which will receive pig manure may be justifiable, as it reduces nutrient leaching from the soil, sequesters C and may allow for higher application rates of pig manure.
Biochar is a stabilized, recalcitrant organic carbon compound, created when biomass is heated to temperatures usually between 300 and 1000 ℃, under low (preferably zero) oxygen concentrations. It is produced from a variety of biomass feedstock, such as agricultural residues, wood chips, manure and municipal solid waste, through a variety of thermal treatments, among which slow pyrolysis is the most widely used due to its moderate operating conditions and optimization of biochar yields. Despite the recent introduction of the term ‘biochar’ for this material, there have been several applications of charred materials in the past due to their unique properties (e.g. high specific surface area, microporosity, and sorptive capabilities). These early applications have primarily focused on the use of biochar as a soil amendment in agriculture, though other applications in environmental remediation engineering may be equally important (i.e. for soil and groundwater treatment and stormwater filter media). The objective of this review is to provide a detailed examination into the engineering properties and potential uses of biochar as an engineered material for environmental remediation. Biochar, due its highly variable and customizable surface chemistry, offers great potential in a variety of engineering applications, some of which have yet to be discovered.
Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the context of the sorption of HOCs onto clay minerals from aqueous and non-aqueous solutions.
Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree. Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. Integr Environ Assess Manag 2014;10:197–209. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC.
Key Points
Passive sampling methods (PSMs) can quantify the freely dissolved concentration (Cfree) of a hydrophobic organic contaminant in sediment. Cfree is directly related to chemical activity, which drives diffusive uptake into benthic organisms and exchange across the sediment-water interface. Cfree and chemical activity offer a well-defined basis for the mechanistic understanding of fate and transport processes in sediments and for predicting adverse effects to benthic organisms. Recent developments in PSMs are advancing practical application to improve risk assessment and management of contaminated sediments.
Experimental data for fluoranthene and feeding selectivity in combination with reaction-diffusion modeling suggest that ingestion of contaminated sediment may often be the dominant uptake pathway for deposit-feeding invertebrates in sediments. A dietary absorption efficiency of 56% and accompanying forage ratio of 2.4 were measured using natural sediment that had been dual-labeled (14C:51Cr) with fluoranthene and fed to the marine deposit-feeding polychaete Capitella species I. Only 3 to 4% of the total absorption could be accounted for by desorption during gut passage. These data were then used as input into a reaction-diffusion model to calculate the importance of uptake from ingested sediment relative to pore-water exposure. The calculations predict a fluoranthene dietary uptake flux that is 20 to 30 times greater than that due to pore water. Factors that act to modify or control the formation of local chemical gradients, boundary layers, or dietary absorption rates including particle selection or burrow construction will be important in determining the relative importance of potential exposure pathways. From a chemical perspective, the kinetics of the adsorption and desorption process are especially important as they will strongly influence the boundary layer immediately surrounding burrowing animals or irrigated tubes. The most important biological factors likely include irrigation behavior and burrow density and size.
In this study, the suitability of biochar and activated carbon (AC) for contaminated soil remediation is investigated by determining the sorption of pyrene to both materials in the presence and absence of soil and before as well as after aging. Biochar and AC were aged either alone or mixed with soil via exposure to (a) nutrients and microorganisms (biological), (b) 60 and 110 °C (chemical), and (c) freeze-thaw cycles (physical). Before and after aging, the pH, elemental composition, cation exchange capacity (CEC), microporous SA, and sorption isotherms of pyrene were quantified. Aging at 110 °C altered the physicochemical properties of all materials to the greatest extent (for example, pH increased by up to three units and CEC by up to 50% for biochar). Logarithmic K(Fr) values ranged from 7.80 to 8.21 (ng kg(-1))(ng L(-1))(-nF) for AC and 5.22 to 6.21 (ng kg(-1))(ng L(-1))(-nF) for biochar after the various aging regimes. Grinding biochar to a smaller particle size did not significantly affect the sorption of d(10) pyrene, implying that sorption processes operate on the subparticle scale. Chemical aging decreased the sorption of pyrene to the greatest extent (up to 1.8 log unit for the biochar+soil). The sorption to AC was affected more by the presence of soil than the sorption to biochar was. Our results suggest that AC and biochar have a high sorption capacity for pyrene that is maintained both in the presence of soil and during harsh aging. Both materials could therefore be considered in contaminated land remediation.
The presence of polycyclic aromatic hydrocarbons (PAHs) in the environment has attracted much concern owing to their mutagenic and carcinogenic properties. Regulatory authorities have favored the use of biological indicators as an essential means of assessing potential toxicity of environmental pollutants. This study aimed to assess the toxicity of acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene to Caenorhabditis elegans by measuring LC50 and EC50 values for growth and reproduction. The exposure to all chemicals was carried out in aqueous medium. All PAHs showed a low acute toxicity to C. elegans. There was no significant mortality in C. elegans after 24 h of exposure at PAH concentrations within (and indeed above) their respective solubility limits. Prolonged exposure (72 h) at high concentrations for acenaphthene (70,573 microg/L), phenanthrene (3758 microg/L), anthracene (1600 microg/L), fluoranthene (1955 microg/L), pyrene (1653 microg/L), and benzo[a]pyrene (80 microg/L) produced mortality. Results also showed that reproduction and growth were much more sensitive parameters of adverse response than lethality, and consequently may be more useful in assessing PAH toxicity using C. elegans. In comparison with previous studies, C. elegans was found to be approximately 2-fold less sensitive to acenaphthene, 5-fold less sensitive to phenanthrene, and 20-fold less sensitive to fluoranthene than Daphnia magna. However, the 48-h LC50 for benzo[a]pyrene (174 microg/L) reported in the present study with C. elegans was similar to that reported elsewhere for Daphnia magna (200 microg/L). Although C. elegans indicated greater sensitivity to benzo[a]pyrene than Artemia salina (174 microg/L vs. 10000 microg/L), the organism showed less sensitivity to pyrene (8 microg/L vs. 2418 microg/L), fluoranthene (40 microg/L vs. 2719 microg/L), and phenanthrene (677 microg/L vs. 4772 microg/L) than Artemia salina. Caenorhabditis elegans, while not the most sensitive of species for PAH toxicity assessment, may still hold applicability in screening of contaminated soils and sediments.
In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.
P‐glycoproteins can cause resistance of mammalian tumor cells to chemotherapeutic drugs. They belong to an evolutionarily well‐conserved family of ATP binding membrane transporters. Four P‐glycoprotein gene homologs have been found in the nematode Caenorhabditis elegans; this report describes the functional analysis of two. We found that PGP‐3 is expressed in both the apical membrane of the excretory cell and in the apical membrane of intestinal cells, whereas PGP‐1 is expressed only in the apical membrane of the intestinal cells and the intestinal valve. By transposon‐mediated deletion mutagenesis we generated nematode strains with deleted P‐glycoprotein genes and found that the pgp‐3 deletion mutant, but not the pgp‐1 mutant, is sensitive to both colchicine and chloroquine. Our results suggest that soil nematodes have P‐glycoproteins to protect themselves against toxic compounds made by plants and microbes in the rhizosphere.
Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are major constraints to potato crop production. We studied the effects of several soil amendments on PCN survival and reproduction in pot experiments. Pig slurry, cattle slurry, mineral nitrogen fertilizer (NH4NO3), crab shell compost and wood chip compost at 170 kg N ha−1 reduced the number of viable eggs in cysts of both PCN species in the absence of potato. This resulted in fewer second-stage juveniles (J2) hatching from these cysts and penetrating potato roots than from cysts of non-amended soils. When potato was planted, the same amendments resulted in less reproduction than in non-amended soil. Most reduction of reproduction was achieved in soils amended with pig slurry (87%) and wood chip compost (82%). Adding biochar at 0.3 and 1% did not reduce the survival or the reproduction of any of PCN species; moreover, it inhibited the suppressing effect of wood chip compost and pig slurry on PCN reproduction when added together with these amendments. The release of ammonium and changes in soil microbial community, determined by phospholipid fatty acid (PLFA) analysis, are involved in nematode suppression in soil amended with pig and cattle slurries. However, the suppressing effect of wood chip and crab shell compost can only be explained by the changes in soil microbiota, while the effect of mineral nitrogen fertilizer can only be related with the production of ammonium. Ammonium and microorganisms most probably have affected PCN directly by killing the eggs and juveniles or indirectly by changing the physiology of the root as mentioned amendments reduced hatch and movement of J2, penetration of the roots and females’ fecundity.
Soils are faced with man-made chemical stress factors, such as the input of organic or metal-containing pesticides, in combination with non-chemical stressors like soil compaction and natural disturbance like drought. Although multiple stress factors are typically co-occurring in soil ecosystems, research in soil sciences on this aspect is limited and focuses mostly on single structural or functional endpoints. A mechanistic understanding of the reaction of soils to multiple stressors is currently lacking.
Analyses were carried out for biochars produced at three temperatures of pyrolysis (400, 600 and 800 °C) from solid residue from biogas production (RBP). Separated and non-separated RBP from biogas plants employing different biogas production conditions were pyrolyzed. The contents of heavy metals and polycyclic aromatic hydrocarbons (PAHs) (16 PAH US EPA) were analyzed in biochars. The analyses showed that with an increased pyrolysis temperature, there was an increase in the contents of PAHs and of certain heavy metals (Cr, Cu, Cd, Pb and Mn). In the ecotoxicological tests, it was noted that the effect depended on the temperature of pyrolysis and on the feedstock from which the biochar was produced. The least harmful effect on the test organisms was from biochar produced by separated RBP in a biogas plant operating in mesophilic conditions. The most negative effect on the test organisms was characteristic of biochar produced from non-separated mesophilic RBP. This study shows that the main factors determining the level of toxicity of biochars produced from RBP towards various living organisms are both the method of feedstock production and the temperature at which the process of pyrolysis is conducted.
Sewage sludge (50% mineral), manure (29%) and wood (<1%) were pyrolyzed at 200, 350 and 500°C with the aim to study the characteristics and sorption potential of materials undergoing pyrolysis across a wide range of mineral contents. A commercial plant-derived biochar (41% mineral) was also considered. The materials were extensively characterized and tested for their sorption towards the model sorbates benzene, naphthalene and pyrene. Plant-derived materials, regardless of their mineral content, developed micropores causing size exclusion of pyrene. Changes in properties and sorption behavior upon pyrolysis were generally consistent for the manure and wood series. A single regression equation developed on our data (including the sorbate hydrophobicity and sorbent polarity) provided excellent prediction of previously reported changes in sorption upon pyrolysis across a wide range of mineral content (up to 500°C). The sewage sludge series, however, followed a particular behavior, possibly due to very high mineral content (up to 67%).
Bioavailability of benzo[a]pyrene (BaP) and 3,3',4,4'-tetrachlorobiphenyl (TCB) was studied in natural lake water containing dissolved organic matter (DOM). Lake water was diluted to give a dissolved organic carbon (DOC) range of I to 20 mg/L. Partition coefficients for the model compounds were assessed at different DOM concentrations and over time with three different methods, namely equilibrium dialysis and reverse-phase and liquid-liquid extraction. In addition, biological partition coefficients were estimated from the difference in the bioconcentration of the model compounds in Daphnia magna in the presence and absence of DOM. Results showed that bioavailability of the model compounds was reduced by the presence of DOM. The equilibrium dialysis method gave the best estimates for bioavailability of the model compounds when compared with biologically determined values. Both the reverse-phase and the liquid-liquid extraction overestimated the bioavailable fraction. The more pronounced overestimation of bioavailable fraction of TCB suggested that the sorption of TCB was not only lower but the interaction was also weaker than that of BaP. Increasing DOM concentration produced lower partition coefficients and the effect seemed to be more pronounced when measured by the reverse-phase and the extraction methods.
The proper choice of exposure times is critical if the freely dissolved concentration of chemicals in soil porewater is to be measured via the equilibrium solid-phase microextraction (SPME) as the times to equilibrium may vary depending on compound and soil properties. To reveal the effects of compound hydrophobicity, ageing and soil organic matter content on times to equilibrium, the SPME uptake was measured for five freshly added and aged hydrophobic organic compounds (phenanthrene, pyrene, lindane, p,p′-DDT and polychlorinated biphenyl (PCB) 153) in two contrasted soils (arable and forest soil). The tested compound-soil systems behaved kinetically different. Longer equilibrium times were observed with increasing hydrophobicity of compounds for aged compared to freshly added chemicals and for the forest soil in comparison to the arable soil. The calculated soil–porewater partition coefficients (i.e. sorption coefficients, Kd) of chemicals differed between soil types mainly due to various organic carbon (OC) contents as evidenced by the comparable Koc values (i.e. Kd values normalised to soil OC content). Similar Koc values were also found with the various extent of ageing, indicating that both the freshly added and aged compounds linearly partitioned between the soil organic matter and porewater. Our results suggest that, for a respective compound, variations in equilibrium times may be expected depending upon the residence time and the organic matter content in soil where the longest equilibrium times seems to appear for a combination of aged compounds and high organic soils. With regard to this outcome, the effect of the level of sample depletion due to the SPME extraction (LDSPME) on equilibrium times was assessed. At LDsSPME of up to 10%, equilibrium times increases linearly with LDsSPME for p,p′-DDT and PCB 153. For phenanthrene (LDSPME<10%), and for lindane and pyrene (1.2% < LDSPME > 40%), no clear relationships were observed.
A solution for environmentally wiser agriculture is the use of composted organic wastes as soil amendments. Just as this alleviates the problem of recycling organic residues, it provides necessary nutrient input for food production. The objective of this work was to study the effect that 13 years of applying three different composted organic wastes or organic amendments have had on soil quality, GHG emissions and the dynamics of its microbial communities 15 days after the annual application. For this purpose, in 1996 a field trial was set up in a Tempranillo vineyard. Since 1998, the applied organic amendments have been as follows: 1. a pelletized organic compost (PEL) made from plant, animal and sewage sludge residues; 2. a compost made from the organic fraction of municipal solid waste (OF-MSW); 3. a compost made of stabilized sheep manure (SMC); 4. a mineral fertilizer (NPK); and 5. an unaltered control. The mean annual doses applied since 1998 have been 3700 kg ha-1 fresh weight (FW) of PEL, 4075 kg ha-1 FW of OF-MSW, 4630 kg ha-1 FW of SMC, and 340 kg ha-1 of NPK treatment. Soil quality was consistently enhanced by amendment application over the 13 years. Total nitrogen was significantly increased in PEL (0.1%), OF-MSW (0.09%) and SMC (0.1%) compared to control (0.06%). Nutrient content was also improved in a similar way, e.g. the most significant increase in P Olsen (80.7 mg kg-1) and K2O (473.8 mg kg-1) was found on SMC. The overall enzyme activity was also increased 15 days after the annual application and OF-MSW had the highest rate (95.9) compared to control (51.3). This increase in metabolic activity was also recorded in GHG emissions. CO2 equivalents per hectare were 1745 kg for OF-MSW and it was the only significant difference found. PEL with 1598 kg and SMC with 1591 kg were not different from the Control (1104 kg). Even though GHG emissions in the soil increased because of the application, soil organic matter content increased significantly (at least 35% more in all organic treatments compared to control) and this rise in organic matter was consistent over the years. According to the results, 85% of the sequences corresponded to 5 main phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria and Gemmatimonadetes, with unclassified material making up for 10.9% (average) of the sequences. Bacterial diversity by Shannon and Chao1 indices was not affected 15 days after the application. However, slight changes in the bacterial community were recorded 15 days after application only in OF-MSW treatment. Assessing soil quality using these three factors allows the relevant agronomical capabilities of the soil to be integrated with the potential effect of this practise on global warming.
This work explored the effect of temperature, production method, and feedstock type on the physicochemical and biological properties of biochars and hydrochars. Biochars and hydrochars made at lower temperatures had higher production rates. Higher pyrolysis temperatures not only increased carbon content of biochars but also produced higher thermal stability biochars that did not start to decompose in air after 400-450 degrees C. The production method showed strong effect on biochar properties. Compared to the dry-pyrolysis biochars derived from the same feedstocks, the hydrochars had more acidic pH values and lower carbon contents. The results showed that feedstock types could also influence characteristics of the biochars. None of the chars showed statistically significant effects on plant seed germination and seedling growth and thus could be used as soil amendments. Our findings indicated that biochars with different properties could be developed by changing production conditions to better satisfy their environmental applications.
The contribution of food to the bioaccumulation of xenobiotics and hence toxicity is still an ambiguous issue. It is becoming more and more evident that universal statements cannot be made, but that the relative contribution of food-associated xenobiotics in bioaccumulation depends on species, substance, and environmental conditions. Yet, small-sized benthic or soil animals such as nematodes have largely been disregarded so far. Bioaccumulation of the polycyclic aromatic hydrocarbon phenanthrene in the absence and presence of bacterial food was measured in the nematode Caenorhabditis elegans. Elimination of phenanthrene in the nematodes was biphasic, suggesting that there was a slowly exchanging pool within the nematodes or that biotransformation of phenanthrene took place. Even with food present, dissolved phenanthrene was still the major contributor to bioaccumulated compound in nematode tissues, whereas the diet only contributed about 9%. Toxicokinetic parameters in the treatment without food were different from the ones of the treatment with bacteria, possibly because nematodes depleted their lipid reserves during starvation.
The thermal conversion (pyrolysis) of biomass for energy production and the incorporation into agricultural soils of the carbon-rich byproduct (biochar) can contribute to the mitigation of climate change. The beneficial effect of biochar on soil fertility and its stability to degradation depends on the interactions of soil and climatic conditions with biochar physicochemical properties, the latter mainly depend on feedstock and pyrolysis conditions. The aim of the present research was to study the effect of pyrolysis temperature on physicochemical properties of miscanthus (Miscanthus × giganteus) biochar and on its short-term stability. Biochar properties were assessed by FTIR spectroscopy, CHN-elemental and simultaneous thermogravimetry (STA) analyses and the short-term stability in a 6-month incubation experiment. All the analytical techniques indicated a threshold value of pyrolysis temperature of 360 °C, above which the thermal and biological resistance to degradation increased dramatically. FTIR spectroscopy showed characteristic absorption bands of cellulose and hemicelluloses (1000–1200 cm−1) in the low-temperature biochars that disappeared in high-temperature biochars. In these latter the absorption peaks associated with aromatic structures increased as confirmed by the decrease of both O/C and H/C ratios. This finding agrees with the STA results showing an increase of DTG temperature peak for high pyrolysis temperatures biochars. The incubation experiment confirmed an increased resistance to biological decomposition of biochar produced at temperatures above 360 °C. The results of the present study demonstrate that biochar thermal and biological stability is affected by pyrolysis temperature in a nonlinear manner.
Biochar (BC) application as a soil amendment has aroused much interest and was found to considerably improve soil nutrient status and crop yields on poor, tropical soils. However, information on the effect of BC on temperate soils is still insufficient, with effects expected to differ from tropical soils. We investigated the effects of BC on soil nutrient dynamics, crop yield, and quality in a greenhouse pot experiment. We compared three agricultural soils (Planosol, Cambisol, Chernozem), and BCs of three different feedstocks (wheat straw [WS], mixed woodchips [WC], vineyard pruning [VP]) slowly pyrolyzed at 525°C, of which the latter was also pyrolyzed at 400°C. The BCs were applied at two rates (1% and 3%, which would correspond to 30 and 90 t ha–1 in the field). Three crops, namely mustard (Sinapis alba L.), barley (Hordeum vulgare L.), and red clover (Trifolium pretense L.) were grown successively within one year. The investigated soil properties included pH, electrical conductivity (EC), cation-exchange capacity (CEC), calcium-acetate-lactate (CAL)–extractable P (PCAL) and K (KCAL), C, N, and nitrogen-supplying potential (NSP). The results show a pH increase in all soils. The CEC increased only on the Planosol. The C : N ratio increased at 3% application rate. Despite improving the soil nutrient status partly, yields of the first crop (mustard) and to a lesser extent of the second crop (barley) were significantly depressed through BC application (by up to 68%); the yield of clover as third crop was not affected. Only the BC from WS maintained yields in the range of the control and even increased barley yield by 6%. The initial yield reduction was accompanied by notable decreases (Cu, Fe, Mn, Zn) and increases (Mo) in micronutrient concentrations of plant tissues while nitrogen concentrations were hardly affected. The results of the pot experiment show that despite additional mineral fertilization, short-term growth inhibition may occur when applying BC without further treatment to temperate soils.
The water solubilities of several polynuclear aromatic and heteroaromatic hydrocarbons have been compiled and reviewed for consistency through correlations with parameters such as surface area, molecular volume, and boiling point. The carbocycles and oxygen and sulfur heterocycles were governed by the same correlative equations, thereby indicating that these heteroatoms entered into only a limited degree of hydrogen bonding. Equations representing the nitrogen heterocycles differed from their carbocyclic counterparts by an approximately constant amount, suggesting that while the solubilizing effect of the nitrogen heteroatom may be large, it tends to remain constant within a similar series of compounds.
Carbonaceous soil amendments are applied to contaminated soils and sediments to strongly sorb hydrophobic organic contaminants (HOCs) and reduce their freely dissolved concentrations. This limits biouptake and toxicity, but also biodegradation. To investigate whether HOCs sorbed to such amendments can be degraded at all, the desorption and biodegradation of low concentrations of (14)C-labelled phenanthrene (⩽5μgL(-1)) freshly sorbed to suspensions of the pure soil amendments activated carbon (AC), biochar (charcoal) and compost were compared. Firstly, the maximum abiotic desorption of phenanthrene from soil amendment suspensions in water, minimal salts medium (MSM) or tryptic soy broth (TSB) into a dominating silicone sink were measured. Highest fractions remained sorbed to AC (84±2.3%, 87±4.1%, and 53±1.2% for water, MSM and TSB, respectively), followed by charcoal (35±2.2%, 32±1.7%, and 12±0.3%, respectively) and compost (1.3±0.21%, similar for all media). Secondly, the mineralization of phenanthrene sorbed to AC, charcoal and compost by Sphingomonas sp. 10-1 (DSM 12247) was determined. In contrast to the amounts desorbed, phenanthrene mineralization was similar for all the soil amendments at about 56±11% of the initially applied radioactivity. Furthermore, HPLC analyses showed only minor amounts (<5%) of residual phenanthrene remaining in the suspensions, indicating almost complete biodegradation. Fitting the data to a coupled desorption and biodegradation model revealed that desorption did not limit biodegradation for any of the amendments, and that degradation could proceed due to the high numbers of bacteria and/or the production of biosurfactants or biofilms. Therefore, reduced desorption of phenanthrene from AC or charcoal did not inhibit its biodegradation, which implies that under the experimental conditions these amendments can reduce freely dissolved concentration without hindering biodegradation. In contrast, phenanthrene sorbed to compost was fully desorbed and biodegraded.
Sediment toxicity testing integrates responses to sediment variables and hence does not directly indicate cause and effect. One tool for determining cause and effect is sediment spiking, in which relatively uncontaminated sediment is amended with known amounts of contaminants, then tested for toxicity. However, sediment spiking methods vary considerably. The present study details appropriate methodologies (dry and wet spiking) for amending sediments with a range of organic contaminant concentrations, i.e., dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyl (PCB). Target and actual concentrations were similar. A dose response was determined for DDT, but PCB was not toxic in an acute sediment toxicity test. Chronic testing of these same sediments is reported in a companion article in this issue.
Batch titration experiments were carried out with organic soil samples in order to investigate the release to the solution phase of humic substances (HS). Measurements were made of pH, dissolved organic carbon (DOC) concentration, and the concentration of mono-meric (inorganic + organic) aluminium, as functions of added acid or base. DOC was taken to be entirely due to HS. The results can be interpreted in terms of a model in which the soil is considered to contain two types of HS–mobile or potentially mobile (HSM), and immobile (HSI). The binding of inorganic ions by the HS is calculated using humic ion-binding model IV, previously developed in this laboratory. Model IV allows the charges on the HS (ZHSM, ZHST) to be calculated; these are determined mainly by the binding of H+ and A13+. Concentrations of HS in solution, [HSaq], are given by the equation:
where |ZHSM| is the modulus of ZHSM, nHSM is the carboxyl group content of HSM, cHSM is the soil content of HSM, β is a fitting parameter, and square brackets, [ ], indicate concentrations. For most of the soils a value for β of 3 gives acceptable agreements between measured and calculated values of [HSaq], indicating a major influence of charge on release. The optimized value of cHSM differs considerably among soils, whereas cHIS varies by only a factor of about two. Total humic contents (cHSM+ cHSI estimated by model optimization are in approximate agreement with values estimated by extraction of the soils with NaOH.
Quantity and quality of dissolved organic matter (DOM) and the time allowed for DOM to interact with organic contaminants can influence their bioavailability. We studied the effect of natural aquatic DOM that had been in contact with benzo[a]pyrene (B[a]P) for 1 to 12 d on the bioconcentration of B[a]P in the nematode Caenorhabditis elegans. Dissolved organic matter quality and quantity was varied by using DOM from three different sources, each in three different concentrations. A model, based on the assumption that only freely dissolved B[a]P is bioavailable, was employed to estimate “biologically determined” partition coefficients [Kp(biol.)]. Expressing the data for each combination of DOM source and contact time in a single Kp (biol.) value allowed a direct comparison of the effects of different DOM qualities and contact times. Our results show that the effect of DOM from a specific source was dependent on DOM quantity, but we also observed a distinct effect of DOM quality (represented by different sampling locations) on the bioconcentration of B[a]P. Contact time had no significant influence for the effects of two DOM sources on the bioconcentration of B[a]P. However, the third DOM source was significantly more effective with increased contact time, leading to lower B[a]P bioconcentration in the nematodes.
SUMMARYCHAOS (Complexation by Humic Acids in Organic Soils) is a quantitative chemical model of organic soils that incorporates complexation by the functional groups of humic substances and non-specific ion-exchange reactions. The two types of interaction are linked by the net humic charge, Z, which depends on the extents of proton and metal complexation, and which in turn determines ionic concentrations in the diffuse part of the electrical double layer, by a Donnan equilibrium. CHAOS was found to account satisfactorily for the results of acid-base titration experiments (pH range 3–5) with soil samples, giving reasonable simultaneous predictions of solution pH and concentration of A13+. Predictive calculations with CHAOS suggest that organic soils acidified by acid rain would respond on a time-scale of years-to-decades to reductions in rain acidity. An associated effect might be an increase in the concentration of dissolved organic matter in the soil solution.
A method is presented for developing water quality criteria (WQC) for type I narcotic chemicals in general and PAHs in particular. The criteria can be applied to any individual or mixture of narcotic chemicals using only the chemical's octanol-water partition coefficient KOW. It is derived from a database of LC50s comprising 156 chemicals and 33 species, including fish, amphibians, arthropods, mollusks, polychaetes, coelenterates, and protozoans. A target lipid model is proposed that accounts for variations in toxicity due to differing species sensitivities and chemical differences. The model is based on the idea that a target lipid is the site of action in the organism. Further, it is assumed that target lipid has the same lipid-octanol linear free energy relationship for all species. This implies that the slope of the log(LC50)–log(KOW) relationship is the same for all species. However, individual species may have varying target lipid body burdens that cause toxicity. The target lipid LC50 body burdens derived from concentration data in the water only are compared to measured total lipid LC50 body burdens for five species. They are essentially equal, indicating that the target lipid concentration is equal to the total extracted lipid concentration. The precise relationship between partitioning in target lipid and octanol is established. The species-specific body burdens are used to determine the WQC final acute value, i.e., the 95-percentile level of protection. An acute-to-chronic ratio is used to compute the body burden corresponding to the WQC final chronic value, which is the procedure used to derive the U.S. Environmental Protection Agency water quality criteria. The criteria are expressed either as dissolved concentrations in the water column or as tissue concentrations.
Nonlinear isotherms were observed for sorption of polycyclic aromatic hydrocarbons (PAHs) to humic materials, but the exact sorption mechanism is not clearly understood. This study aimed to investigate the sorption of PAHs by compost humic materials. Humic acids (HAs) were progressively extracted from two compost samples by a 0.1-M sodium pyrophosphate solution. Sorption of phenanthrene by the extracted HAs was studied with a batch equilibration technique. Competitive sorption between pyrene and phenanthrene in the HAs was also examined. Elemental analysis and solid-state 13C NMR were used to characterize HAs. All sorption isotherms were nonlinear although these samples contained little black carbons if any. Isotherm linearity increased with increasing number of extractions. Isotherm nonlinearity was negatively related to HA aliphaticity. Addition of pyrene to the phenanthrene-HA system increased isotherm linearity. Competition between phenanthrene and pyrene sorption was more pronounced in the first fraction of HAs with a higher content of aromatic moieties. This study showed that humic materials alone could lead to nonideal sorption for PAHs.
A ring test was carried out within the standardization process of ISO 10872 to evaluate the precision of the toxicity test for the nematode Caenorhabditis elegans. Eight different laboratories tested aqueous solutions of the reference substance benzylcetyldimethylammonium chloride as well as native sediments and soils for toxic effects on the growth and reproduction of C. elegans. Validity criteria were met in all laboratories. Average median- and low-effect concentrations were determined to be 15.1 mg L(-1) (EC50) and 8.7 mg L(-1) (EC10) for growth and 7.5 mg L(-1) (EC50) and 3.8 mg L(-1) (EC10) for reproduction of C. elegans, with ECx values showing a high degree of reproducibility (CV(R) : <21% and <11% for EC10 and EC50, respectively) and repeatability (CV(r) : <20% and <7% for EC10 and EC50, respectively). The toxic effects of the sediments and soils revealed by the different laboratories were well related to each samples' degree of chemical contamination. Moreover, the effects showed an acceptable reproducibility (CV(R) : 5-33% and 0-28% for growth and reproduction, respectively) and repeatability (CV(r) : 3-13% and 0-12% for growth and reproduction, respectively). The present study confirms that the toxicity test with C. elegans according to ISO 10872 is a reliable and precise tool to assess the toxicity of aqueous media, freshwater sediments, and soils.
Nematodes, the earth’s most abundant metazoa, are ubiquitous in the soil environment. They are sufficiently large to be identifiable by light microscopy and sufficiently small to inhabit water films surrounding soil particles. They aggregate around and in food sources. They include component taxa of the soil food web at several trophic levels. They can be categorized into functional guilds whose members respond similarly to food web enrichment and to environmental perturbation and recovery. Indices derived through nematode faunal analysis provide bioindicators for disturbance of the soil environment and condition of the soil food web. We enhance the resolution of faunal analyses by providing a weighting system for the indicator importance of the presence and abundance of each functional guild in relation to enrichment and structure of the food web. Graphical representations of food web structure, based on nematode faunal analyses, allow diagnostic interpretation of its condition. Simple ratios of the weighted abundance of representatives of specific functional guilds provide useful indicators of food web structure, enrichment, and decomposition channels.
We studied the effects of in situ remediation of a heavy metal (HM) contaminated soil on some soil chemical properties, microbial function and microbial structural diversity after 18 months. The experiment was carried out at semifield scale in containers filled with HM contaminated soil from the Aznalcóllar mine accident (Southern Spain, 1998). The remediation measures consisted of the application of different amendments and/or establishment of a plant cover (Agrostis stolonifera L.). Seven treatments were established: four organic treatments (municipal waste compost (MWC), biosolid compost (BC), leonardite (LEO) and litter (LIT)), one inorganic treatment (sugar beet lime (SL)) and two controls (control with plant cover (CTRP) and control without plant cover (CTR)). Several soil chemical (pH, soluble HM, total organic C (TOC), water-soluble C (WSC) and available-P) and biochemical properties (microbial biomass C (MBC), MBC/TOC ratio and enzyme activities) were determined. Microbial community structure was studied by means of ARDRA (amplified ribosomal DNA restriction analysis). The SL, MWC and BC treatments were the most efficient to raise soil pH and decrease soluble HM concentrations. Total organic C was increased in the organic treatments by 2 to 4-fold, whereas water-soluble C was statistically similar in the CTRP, SL and the organic treatments, probably due to the presence of a root system in all these treatments. Available-P was also increased in the BC, SL and MWC treatments due to the higher P content of the amendments applied in these treatments. Soil microbial function was generally enhanced in the amended and CTRP treatments. The MWC, BC and SL treatments were particularly efficient to increase microbial biomass C, the MBC/TOC ratio and the dehydrogenase and aryl-sulphatase enzyme activities. These results could be attributed to the amelioration of some of the soil chemical properties: increase in soil pH and water-soluble C and decrease of HM soluble concentrations. ARDRA analyses showed changes in structural diversity in both the bacterial and fungal community under the different treatments. Fingerprinting patterns of the 16S rDNA obtained with Hinf-I and of the 18S rDNA with Hpa-II revealed higher similarity percentages among samples from the same treatment compared with samples from the other treatments. In addition, a higher similarity was found between samples from all treatments under the Agrostis influence. The use of certain amendments and/or a plant cover is important for in situ remediation of HM contaminated soils, since these practices can affect soil chemical properties, as well as the microbial community function and structure.
Biochars are biological residues combusted under low oxygen conditions, resulting in a porous, low density carbon rich material. Their large surface areas and cation exchange capacities, determined to a large extent by source materials and pyrolysis temperatures, enables enhanced sorption of both organic and inorganic contaminants to their surfaces, reducing pollutant mobility when amending contaminated soils. Liming effects or release of carbon into soil solution may increase arsenic mobility, whilst low capital but enhanced retention of plant nutrients can restrict revegetation on degraded soils amended only with biochars; the combination of composts, manures and other amendments with biochars could be their most effective deployment to soils requiring stabilisation by revegetation. Specific mechanisms of contaminant-biochar retention and release over time and the environmental impact of biochar amendments on soil organisms remain somewhat unclear but must be investigated to ensure that the management of environmental pollution coincides with ecological sustainability.
The combined effects of DOM and biosurfactant on the sorption/desorption behavior of phenanthrene (PHE) and pyrene (PYR) in soil water systems were systematically investigated. Two origins of DOMs (extracted from soil and extracted from food waste compost) and an anionic biosurfactant (rhamnolipid) were introduced. The presence of DOM in the aqueous phase could decrease the sorption of PAHs, thus influence their mobility. Desorption enhancement for both PHE and PYR in the system with compost DOM was greater than that in the soil DOM system. This is due to the differences in specific molecular structures and functional groups of two DOMs. With the co-existence of biosurfactant and DOM, partitioning is the predominant process and the desorption extent was much higher than the system with DOM or biosurfactant individually. For PHE, the desorption enhancement of combined DOM and biosurfactant was larger than the sum of DOM or biosurfactant; however desorption enhancement for PYR in the combined system was less than the additive enhancement in two individual system under low PAH concentration. This could be explained as the competition sorption among PAHs, DOM and biosurfactant. The results of this study will help to clarify the transport of petroleum pollutants in the remediation of HOCs-contaminated soils.
Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) was measured in the deposit-feeding oligochaete Ilyodrilus templetoni exposed for 28 d to Anacostia River sediment (Washington, DC, USA) and to an initially uncontaminated sediment from Brown Lake (Vicksburg, MS, USA) sequentially diluted with 3 to 25% contaminated New Bedford Harbor sediment (New Bedford, MA, USA). The Anacostia River sediment studies represented exposure to a historically contaminated sediment with limited availability, whereas exposure to the other sediment included both the historically contaminated New Bedford Harbor sediment and fresh redistribution of contaminants into the Brown Lake sediments. Organism tissue concentrations did not correlate with bulk sediment concentrations in the Anacostia River sediment but did correlate with the sequentially diluted sediment. Porewater concentrations measured via disposable solid-phase microextraction fiber (SPME) with polydimethylsiloxane (PDMS), however, correlated well with organism uptake in all sediments. Bioaccumulation was predicted well by a linear relationship with the product of porewater concentration and compound octanol-water partition coefficient (Anacostia, slope = 1.08, r² = 0.76; sequentially diluted sediments, slope = 1.24, r² = 0.76). The data demonstrate that the octanol-water partition coefficient is a good indicator of the lipid-water partition coefficient and that porewater concentrations provide a more reliable indicator of bioaccumulation in the organism than sediment concentrations, even when the route of uptake is expected to be via sediment ingestion.
Solid-phase microextraction (SPME) has shown potential as an in situ passive-sampling technique in aquatic environments. The reliability of this method depends upon accurate determination of the partition coefficient between the fiber coating and water (K(f)). For some hydrophobic organic compounds (HOCs), K(f) values spanning 4 orders of magnitude have been reported for polydimethylsiloxane (PDMS) and water. However, 24% of the published data examined in this review did not pass the criterion for negligible depletion, resulting in questionable K(f) values. The range in reported K(f) is reduced to just over 2 orders of magnitude for some polychlorinated biphenyls (PCBs) when these questionable values are removed. Other factors that could account for the range in reported K(f), such as fiber-coating thickness and fiber manufacturer, were evaluated and found to be insignificant. In addition to accurate measurement of K(f), an understanding of the impact of environmental variables, such as temperature and ionic strength, on partitioning is essential for application of laboratory-measured K(f) values to field samples. To date, few studies have measured K(f) for HOCs at conditions other than at 20° or 25 °C in distilled water. The available data indicate measurable variations in K(f) at different temperatures and different ionic strengths. Therefore, if the appropriate environmental variables are not taken into account, significant error will be introduced into calculated aqueous concentrations using this passive sampling technique. A multiparameter linear solvation energy relationship (LSER) was developed to estimate log K(f) in distilled water at 25 °C based on published physicochemical parameters. This method provided a good correlation (R(2) = 0.94) between measured and predicted log K(f) values for several compound classes. Thus, an LSER approach may offer a reliable means of predicting log K(f) for HOCs whose experimental log K(f) values are presently unavailable. Future research should focus on understanding the impact of environmental variables on K(f). Obtaining the data needed for an LSER approach to estimate K(f) for all environmentally relevant HOCs would be beneficial to the application of SPME as a passive-sampling technique.
Applying amendments to multi-element contaminated soils can have contradictory effects on the mobility, bioavailability and toxicity of specific elements, depending on the amendment. Trace elements and PAHs were monitored in a contaminated soil amended with biochar and greenwaste compost over 60 days field exposure, after which phytotoxicity was assessed by a simple bio-indicator test. Copper and As concentrations in soil pore water increased more than 30 fold after adding both amendments, associated with significant increases in dissolved organic carbon and pH, whereas Zn and Cd significantly decreased. Biochar was most effective, resulting in a 10 fold decrease of Cd in pore water and a resultant reduction in phytotoxicity. Concentrations of PAHs were also reduced by biochar, with greater than 50% decreases of the heavier, more toxicologically relevant PAHs. The results highlight the potential of biochar for contaminated land remediation.
The purpose of this study was to assess the suitability of applying equilibrium partitioning (EqP) theory to predict the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) by earthworms when these are exposed to contaminated soils in the field. Studies carried out in situ in various contaminated floodplain sites showed the presence of linear relationships with intercept zero between the lipid-normalized concentration of different PAHs in the earthworm Lumbricus rubellus and the organic-matter-normalized concentration of the compounds in soil. The demonstration of such an isometric relationship is in agreement with the prediction of EqP theory that the biota-soil accumulation factor (BSAF) should be independent of the octanol/water partition coefficient, log K(ow). The average BSAF of PAH compounds in the sampled 20-cm top layer of soil was 0.10 (range, 0.03- 0.26). The present study also investigated the route of uptake of PAHs for earthworms in soil. The bioconcentration factor of low-molecular-weight PAHs, such as phenanthrene, fluoranthene, and pyrene, was derived from bioconcentration kinetic modeling of water-only experiments and found to be of the same order of magnitude as the bioaccumulation factor in the field when the latter was normalized to calculated concentrations in soil pore water. The results indicated that the exposure of earthworms to PAHs in soil is mediated through direct contact of the worms with the dissolved interstitial soil-water phase, further supporting the applicability of EqP theory to PAHs. Our experimental data on the biotransformation of PAHs suggest that earthworms possess some capacity of metabolization, although this does not seem to be a major factor in the total elimination of these compounds. Even though the EqP approach was found to be applicable to low- molecular-weight PAHs with respect to the prediction of bioaccumulation by earthworms in the field, the results were less conclusive for high- molecular-weight compounds, such as benzo[a]pyrene.
The nature of soil organic matter (SOM) functional groups associated with sorption processes was determined by correlating partitioning coefficients with solid-state (13)C nuclear magnetic resonance (NMR) and diffuse reflectance mid-infrared (DRIFT) spectral features using partial least squares (PLS) regression analysis. Partitioning sorption coefficients for n-pentadecane (n-C(15)) were determined for three alternative models: the Langmuir model, the dual distributed reactive domain model (DRDM) and the Freundlich model, where the latter was found to be the most appropriate. NMR-derived constitutional descriptors did not correlate with Freundlich model parameters. By contrast, PLS analysis revealed the most likely nature of the functional groups in SOM associated with n-C(15) sorption coefficients (K(F)) to be aromatic, possibly porous soil char, rather than aliphatic organic components for the presently investigated soils. High PLS cross-validation correlation suggested that the model was robust for the purpose of characterising the functional group chemistry important for n-C(15) sorption.