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Effects of sewage sludge amendment on snail growth and trace metal transfer in the soil-plant-snail food chain
Abstract
Cu, Zn, Pb, and Cd concentrations in a soil plant (Lactuca sativa) continuum were measured after sewage sludge amendment. The effects of sewage sludge on growth and trace metal bioaccumulation in snails (Cantareus aspersus) were investigated in a laboratory experiment specifically designed to identify contamination sources (e.g., soil and leaves). Application of sewage sludge increased trace metal concentrations in topsoil. However, except Zn, metal concentrations in lettuce leaves did not reflect those in soil. Lettuce leaves were the main source of Zn, Cu, and Cd in exposed snails. Bioaccumulation of Pb suggested its immediate transfer to snails via the soil. No apparent toxic effects of trace metal accumulation were observed in snails. Moreover, snail growth was significantly stimulated at high rates of sludge application. This hormesis effect may be due to the enhanced nutritional content of lettuce leaves exposed to sewage sludge.
... In France, for example, 73% of municipal sludge is currently considered to be of value in agriculture (Legroux and Truchot, 2009). Recently, however, farmers have shown reluctance towards sludge as they have been heavily influenced by a negative public opinion about certain pollutants, emanations of unpleasant odors and real concerns about healthrelated risks (Bourioug et al., 2015a). ...
... However, there are various types of contaminants present in SS such as trace metals, organic pollutants, medically active substances, etc. Sludge spreading therefore requires intensive monitoring of ecosystem components such as plants, soil, water and fauna to identify any possible positive or negative impacts on plant productivity, on the environment and on human health (Carnus and Thomas-Chery, 2007;Bourioug et al., 2015a). ...
Sewage sludge application in forest plantations is an interesting complementary alternative practice to sewage
sludge reutilization and recycling,with a significant and sustainable net effect in climate change mitigation. However, to optimize it a detailed knowledge of its effects on ecosystem components such as plants, soil, water and fauna is needed. We investigated the effects of sewage sludge application on soil, tree growth and floristic diversity in a ten-year-old plantation of European larch (Larix decidua Mill.). Our one-hectare study site, located at Mélisey, Haute-Saône, France (47°753′ Lat., 6°580′ Long.), was subdivided into six plots. Three plots, alternating with three control plots (no sewage sludge application),were amended in June 2008 with 0.4 tDWha−1 obtained from a municipal urban wastewater treatment plant in Mélisey. Within each plot, one subplot was delimited and sludge was again manually applied at 3 t of DW ha−1 in July 2009 and March 2010 to the soil surface of the amended subplots without incorporation. The results showed no effect on radial and height growth of European larch amended with 0.4 t DWha−1. While a significant temporary increase in pH, macro-element contents (N, P and Ca) and the trace metal (Cu and Zn) concentration in the soil was observed, it had no significant effect on needles and sporocarp contents. The number of species in the amended subplots with 3 t DW ha−1 year−1 increasedby 80% compared to the control. However, the relative species abundance present only in amended subplots remains b1, except for Hypericum humifusum.
... Therefore, the assessment of pollution effects on this organism could also be of concern for potential effects of human health, due to the human consumption of this species. Cornu aspersum have shown to accumulate pollutants from contaminated soils (Bourioug et al. 2015). However, a limited number of studies exists supporting land snails as a potential bioindicator species for assessing the risk of environmental contamination (El-Gendy et al. 2011;Itziou and Dimitriadis 2009;Regoli et al. 2006), and more specifically Cornu aspersum as a sentinel organism for both trace metal and organic pollution (Leomanni et al. 2015(Leomanni et al. , 2016. ...
The use of organisms in biomonitoring studies allows the determination of the pollution levels, the assessment of the quality of the enviroment and the study of toxic effects of pollutants on the organisms. By studying the responses (biomarkers) of organisms it is possible to assess the exposure and effects of pollutants. Land gastropods are widely used in relevant studies as they possess several characteristics that make them ideal for use as bioindicators. In the present study we sought to evaluate several biomarkers in the laboratory using snails of the species Cornu Aspersum after the exposure to heavy metals (Cd, Hg) and a mixture of polycyclic aromatic hydrocarbons (PAHs) (anthracene phenanthrene and naphthalene). The biomarkers studied were the following: lysosomic membrane stability using the neutral red retention assay (NRR), the production of reactive oxygen species (ROS) using the compound DCFH-DA and flow cytometry, lipid peroxidation using the TBARs assay that measures the concentration of malondialdehyde (MDA), protein carbonylation (-CO) using ELISA, and single strand breaks of DNA using the comet assay. Our results show significant differences in the responses between the control group and the groups that were exposed to pollutans, enhancing the role of Cornu aspersum as a promising bioindicator organism in terrestrial pollution studies with the use of the biomarkers applied.
... Specifically, the comparative results showed that (a) the values of total organic matter (TOM), cation exchange capacity (CEC), total dissolved solids (TDS), total nitrogen (TN), and total phosphorus (TP) in S2 significantly increased, indicating that soil fertility was improved by MSC nutrients; (b) the pH and carbonate concentration in S2 significantly decreased because of the dilution effect and neutralization effect, but fortunately the amended-LS was still alkaline (pH ≥ 7.69); (c) the total HMs concentrations in S2 were less than the national limit values, although they were significantly increased. The CF indices of Cd, Cu, and Zn were 2.1, 1.2, and 2.0, respectively, and demonstrated that addition of higher doses of sewage sludge or MSC induces increased HMs concentrations in the amended soil (Achiba et al. 2009;Bourioug et al. 2015). ...
Municipal sludge compost (MSC) is commonly used as fertilizer or an amendment in barren soils. However, MSC-borne Cd is of great concern in food safety because of its toxicity. Loess subsoil (LS) is barren and lacks nutrients, but it has a strong ability to absorb and stabilize heavy metals. Hence, LS may be amended with MSC and may reduce the bioavailability of Cd. To simulate the dose effect of the accumulated MSC-borne Cd in amended LS, pot experiments were conducted to study the bioavailability of Cd and other mineral nutrition elements in broad bean (Vicia faba L.) under Cd stress. Plant height and dry biomass remarkably increased as the physicochemical properties of LS were significantly improved; however, they were not significantly influenced by the added Cd. The Cd in the plants grown in MSC amended-LS (P2) mainly accumulated in roots (32.12 mg kg⁻¹) and then in stems and leaves (6.00 mg kg⁻¹). Less Cd (0.74 mg kg⁻¹) accumulated in the edible parts, where the Cd concentration was 53% lower than that in the edible parts of plants grown in LS (P1). The decreased Cd concentrations in the P2 beans may be due to the biomass dilution effect. Notably, the Cd concentrations in the beans exceeded the national safety limit value (0.2 mg kg⁻¹) when the Cd treatment levels exceeded 2 mg kg⁻¹ in LS and 6 mg kg⁻¹ in amended LS. The MgCl2 extraction procedures can be used to assess Cd bioavailability in amended soil-plant systems. The potential antagonism of Zn and Cu against Cd toxicity in the soil-plant system may explain why this plant can tolerate higher Cd concentrations after MSC application.
... Though the concentrations of these potentially toxic elements in TW are low, long-term use of this water on agricultural lands often results in the build-up in the soils of high levels of these contaminants (Al Omron et al., 2012). Once accumulated, TMs are highly persistent in the topsoil and can cause potential problems or an increased transfer into the food chain (Bourioug et al., 2015a(Bourioug et al., , 2015b, which may pose a serious risk to human health (Wang et al., 2003). The TM persistence in the top layer depends heavily on soil pH, OM, redox condition and clay content (Hue and Ranjith, 1994;Richards et al., 2000;Singh and Agrawal, 2008;Grisey and Aleya, 2015). ...
tIn the arid climate of Djibouti, salt concentrations of up to 1200 mg L−1have been recorded in well water,attributed to the overexploitation of aquifers. Farmers are therefore turning to untreated wastewater asa source of water for crop irrigation. The authors undertook a study in two phases. In the first phase theytested the field transposition of an experimental water treatment method previously laboratory-testedon a small scale. The pilot device was composed of an adaptor basin for the wastewater, a filter basinfilled with sand and a storage basin to collect and hold the treated water. Transfer of waters from basinto basin was gravitational. The physicochemical and microbiological sleek raw water parameters weredetermined weekly for 7 weeks. Monitoring of chemical oxygen demand concentrations decreased from445 ± 5.76 mg L−1O2on the first day of the experiment to 101 ± 1.34 mg L−1O2on the 21st day. Theremoval of total coliforms attained more than 99.6% as of day 21. The performance of the microbiologicaltreatment of waters obtained through sand filtration is therefore of definite interest in agriculture. In thesecond phase the effect of different irrigation waters (untreated wastewater (WW), treated wastewater(TW), saline well water (SW), mixed water (MW) and potable water (PW)) on growth and yield of thegrass Panicum maximum were also compared. The use of WW and TW in irrigation effectively increasedstem height and aerial part dry matter compared to other treatments, while irrigation with SW and PWshowed the lowest measured values. Depending on their performance, the effectiveness of the treatedwaters can be ranked in the following increasing order: TW; WW > MW > PW; SW. The performance ofthe TW treatment can be explained by its higher nutritive content, especially in N.
... Though the concentrations of these potentially toxic elements in TW are low, long-term use of this water on agricultural lands often results in the build-up in the soils of high levels of these contaminants (Al Omron et al., 2012). Once accumulated, TMs are highly persistent in the topsoil and can cause potential problems or an increased transfer into the food chain (Bourioug et al., 2015a(Bourioug et al., , 2015b, which may pose a serious risk to human health (Wang et al., 2003). The TM persistence in the top layer depends heavily on soil pH, OM, redox condition and clay content (Hue and Ranjith, 1994;Richards et al., 2000;Singh and Agrawal, 2008;Grisey and Aleya, 2015). ...
The use of biosolids in agriculture contributes to soil fertility and plant nutrition. However, the presence of potentially toxic elements (PTEs) can limit its use as a fertilizer. In this context, we propose to evaluate PTEs bioaccumulation in lettuce and soil fertility treated with biosolid. The experiment was conducted in a completely randomized design with five replications. The treatments consisted of five doses of biosolids (0, 20, 40, 60, and 80 t ha−1) in an Oxisol. The fresh and dry matter of the aerial part and root of lettuce, PTEs concentration in the leaves of lettuce, and the soil chemical fertility after the application of the biosolid were determined. The biosolid application increased soil fertility, enhance soil pH, cation exchange capacity, and organic carbon concentration, providing greater production of lettuce fresh matter (121 g per plant at a dose of 67 t ha−1). With the increment of biosolid doses, a reduction in the concentration of As, Cr, Cu, Ni, Se, and Zn in lettuce leaves was observed. There was a negative correlation between the PTEs concentration in the plants and the soil attributes, which represents a reduction in the PTEs bioavailability as biosolid dose increases. However, the levels of Cd and Pb were above the limit established by Brazilian resolution for consumption, with or without biosolid application, indicating a high natural concentration of these elements in the soil. Biosolid increased soil fertility and lettuce production and decreased PTEs concentration in the leaves of lettuce.
The application of sewage sludge (SS) in forestry is considered a viable option. However, the long-term application of SS potentially leads to metal accumulation, posing an environmental risk. Understanding the loading capacity of SS for forestry application is therefore of great significance. We used data from published studies and statistical bulletins across 31 provincial capital cities (PCCs) in China to calculate the loading capacity (LC) of SS for forestry application for each PCC. The results are as follows: (1) the mean value of the priority control threshold was 33 t·ha −1 ·y −1 in 31 PCCs, while the variations ranged from 7 to 91 t·ha −1 ·y −1 among different PCCs. The priority control thresholds (S min s) of 1/2 PCCs were higher than 30 t·ha −1 ·y −1 (CJ-T 362-2011). The S min values of Lanzhou, Tianjin, Hohhot, Shanghai, and Yinchuan were above 55 t·ha −1 ·y −1 , but S min values of Kunming and Changsha were below 10 t·ha −1 ·y −1. (2) Cd was the priority control metal in most of the PCCs (27/31), with the exception of Shanghai and Guangzhou (Cu), Beijing (Hg), and Tianjin (Zn). (3) The total loading capacity was 507 million t·y −1 , which was 125 times higher than the total quantity of the dry SS (404 × 10 4 t) for the 31 PCCs. Our results have important practical significance for the use of urban sludge forest land in China and suggest that SS disposal policies need to be tailored to specific regions. We provide a scientific basis to guide the development of national and provincial forestry policies.
Trace element solubility and availability in land-applied residuals is governed by fundamental chemical reactions between metal constituents, soil, and residual components. Iron, aluminum, and manganese oxides; organic matter; and phosphates, carbonates, and sulfides are important sinks for trace elements in soil-residual systems. The pH of the soil-residual system is often the most important chemical property governing trace element sorption, precipitation, solubility, and availability. Trace element phytoavailability in residual-treated soils is often estimated using soil extraction methods. However, spectroscopic studies show that sequential extraction methods may not be accurate in perturbed soil-residual systems. Plant bioassay is the best method to measure the effect of residuals on phytoavailability. Key concepts used to describe phytoavailability are (i) the salt effect, (ii) the plateau effect, and (iii) the soil-plant barrier. Metal availability in soil from metal-salt addition is greater than availability in soil from addition of metal-containing residuals. Plant metal content displays plateaus at high residual loadings corresponding to the residual's metal concentration and sorption capacity. The soil-plant barrier limits transmission of many trace elements through the food chain, although Cd (an important human health concern) can bypass the soil-plant barrier. Results from many studies that support these key concepts provide a basis of our understanding of the relationship between trace element chemistry and phytoavailability in residual-treated soils. Research is needed to (i) determine mechanisms for trace element retention of soil-residual systems, (ii) determine the effect of residuals on ecological receptors and the ability of residuals to reduce ecotoxicity in metal-contaminated soil, and (iii) predict the long-term bioavailability of trace elements in soil-residual systems.
In most Brazilian cities sewage sludge is dumped into sanitary landfills, even though its use in forest plantations as a fertilizer and soil conditioner might be an interesting option. Sewage sludge applications might reduce the amounts of mineral fertilizers needed to sustain the productivity on infertile tropical soils. However, sewage sludge must be applied with care to crops to avoid soil and water pollution. The aim of our study was to assess the effects of dry and wet sewage sludges on the growth and nutrient cycling of Eucalyptus grandis plantations established on the most common soil type for Brazilian eucalypt plantations. Biomass production and nutrient cycling were studied over a 36-month period in a complete randomized block design. Four experimental treatments were compared: wet sewage sludge, dry sludge, mineral fertilizer, and no fertilizer applications. The two types of sludges as well as mineral fertilizer increased significantly the biomass of Eucalyptus trees. Wood biomass productions 36 months after planting were similar in the sewage sludge and mineral fertilization treatments (about 80 tons ha−1) and 86% higher than in the control treatment. Sewage sludge application also affected positively leaf litter production and significantly increased nutrient transfer among the components of the ecosystem.
Two solution studies were conducted a) to investigate the uptake of zinc (Zn) and cadmium (Cd) by rice plants (Oryza sativa L.) and interaction between these elements, and b) to determine experimental conditions for growing rice grain with desired Cd concentration for an animal feeding study. In both studies, free metal activities of cadmium and cationic microelements were buffered by an excess of chelating agents. The first study was a factorial design with two Zn levels (1.0 and 3.89 ÂμM) and four Cd levels (0.81, 1.44, 2.56 and 4.55 ÂμM) in the solution. In the second study, rice was grown in two solutions of different micro- and macro-element compositions and three Cd levels (0.0, 0.5, and 2.0 ÂμM). In the first study, solution Zn concentration of 3.89 ÂμM and corresponding free metal activity (pZn) of 6.00 was toxic to young rice plants. With time, Zn concentrations in rice plants decreased while Cd concentrations increased. Toxic concentration of Cd in roots (about 100 mg kg) associated with a 20% reduction in the root dry matter occurred at the free Cd activities in the solution (pCd) in the range of 10.25–9.75. Sufficient Zn level in plants slightly stimulated Cd transfer from roots to shoots as opposed to barely sufficient or slightly deficient Zn concentration in shoots. However, the better Zn status in plants clearly diminished severity of Cd toxicity symptoms in shoots. The use of nutrient solutions adapted for rice growth allowed the rice grown in the second experiment to produce grain under controlled conditions. Cadmium in the brown rice grain was 0.1 to 0.8 mg kg, covering the range needed for feeding experiments relevant to rice Cd risk to humans. Composition of the nutrient solutions, in addition to solution Cd level, had a significant effect on Cd concentration in grain. Correlation of grain Cd concentration with solution Cd activity was much stronger than with total solution Cd. Results of both experiments supported hypothesis that Cd uptake and transport within rice plants is an active process.
Food consumption and growth variations related to several dosages of heavy metals (Cu, Zn, Hg and Pb) in diet were studied
in the terrestrial slug Arion ater for 27 days of experimental treatment.
The work reported here is part of a larger project to investigate the histological effects of metal exposure in pulmonate
gastropods.
Graphics on food consumption and growth vs. time for each metal, and regression for each behaviour observed are presented.
This book presents a synthesis of current knowledge and research on the biology of terrestrial gastropod molluscs, which are of importance to human societies as food, medicine, crop pests, vectors of parasites, and as tools, personal ornamentation and currency in trade. It covers the morphology, phylogeny and systematics, structure and function of the various organ systems, feeding behaviour, life history strategies, behavioural ecology, population and conservation genetics, and soil biology and ecotoxicology of the terrestrial molluscs.
Vegetable production with organic farming has been practiced by many farmers in Japan. However, one of the problems is the yield lower than that by chemical farming. In this study, Two leafy vegetables were grown with organic fertilization in comparison with chemical fertilization, to see what accounts the yield limitation and how different in quality of the leafy vegetables between organic and chemical fertilizations. Leaf-picking harvest was adopted to extend the growth and harvest period. Growth at the early stage was lower in organic than in chemical fertilization treatments, which was attributed to the lower available nutrients in organic fertilizer. However, at later stages both the two vegetables in organic fertilization treatments grew better and resulted in a final higher total yield than those in chemical fertilization treatments, which was attributed to the high nutrient sustainability of organic fertilizer and the improved biological properties of the soil. Leaf concentrations of sugars and vitamin C were significantly higher and nitrate was lower in organic-fertilized than chemical-fertilized vegetables. It is possible for organic farming to produce vegetables with a high quality and a yield higher than or similar to that of chemical farming if the nutrient supply is sufficient. The yield of leafy vegetables was higher than that of chemical farming when the leaf-picking harvest was adopted to extend the growth and harvest period.
Growth and reproduction of the snail Helix aspersa (Müller) var. maxima were examined at four combinations of temperature and artificial photoperiod and in transparent and opaque containers at two temperatures for over 40 weeks. Effects of temperature on both processes predominated. However, following 10 weeks of oviposition at optimum temperature (20°C), absence of photoperiod inhibited egg-laying throughout a further 15 weeks. Following inhibition of oviposition, the albumen gland atrophied, indicating the storage of secretory products.
Snail growth was improved by rearing in opaque rather than transparent containers in a long-day photoperiod. Snail oviposition was unaffected by container type throughout a 28-week period, demonstrating an acute perception of photoperiodicity by snails maintained at low light intensity.
Nutritional micronutrient deficiencies and exposure to pollutant metals threaten human health globally. Plant crops are at
the beginning of a food chain that largely determines food metal contents. In order to survive, all organisms have to supply
appropriate amounts of each micronutrient to the correct target apometalloproteins and at the same time avoid adventitious
metal binding to non-target metal binding sites or other cellular compounds. This requires the operation of metal homeostasis
networks, which orchestrate the mobilization, uptake, distribution, intracellular trafficking, chelation, and sequestration
of all metal ions. Presumably as a result of time-dependent and local variations in bioavailable soil metal concentrations,
plant metal homeostasis networks exhibit a remarkably high degree of plasticity and natural diversity. This is a review covering
the current knowledge of metal-dependent processes and proteins, metal homeostasis and its regulation, and the molecular mechanisms
underlying naturally selected metal hypertolerance and metal hyperaccumulation in higher plants.
Tree–understory competition is one of the most important aspects that control tree growth after reforestation. The relationship
between trees and the understory can be modified by improving acidic soils with lime and by fertilisation. This experiment
aims to evaluate the effect of soil improvements on the pasture–tree relationship by liming and fertilisation on different
dates in a Pinus radiata-reforested area. Both lime and sewage sludge improved soil fertility by increasing Ca and reducing Al in the soil. Initially,
tree development was reduced by lime, which improved the establishment of competitive grasses. Tree growth in limed treatments
did not initially respond to sludge inputs, likely because both tree and grass roots shared the same soil depth layer. Three
years after establishment, the use of high doses of sewage sludge in limed plots caused a growth rate similar to the best
treatments of unlimed plots, which grew with a poorly sown grass establishment. After 2years of the experiment, the presence
of Erica woody shrub diminished tree development. High doses of sewage sludge with lime, as well as high doses of sewage sludge without
lime, applied in April and low doses of sewage sludge without lime added in early February improved tree growth. From a practical
point of view, lime and sewage sludge dose close to 100kg total Nha−1 should be recommended if a silvopastoral system is established, as it enhances pasture production and tree growth.
KeywordsOrganic fertiliser–Herbaceous–Shrubs–Aluminium–Calcium–Biosolid
Municipal wastewater treatment results to the production of large quantities of sewage sludge, which requires proper and environmentally accepted management before final disposal. In European Union, sludge management remains an open and challenging issue for the Member States as the relative European legislation is fragmentary and quite old, while the published data concerning sludge treatment and disposal in different European countries are often incomplete and inhomogeneous. The main objective of the current study was to outline the current situation and discuss future perspectives for sludge treatment and disposal in EU countries.
Atmospheric pollution from vehicular traffic is a matter of growing interest, often leading to temporary restrictions in urban areas. Although guidelines indicate limits for several parameters, the real toxicologic impacts remain largely unexplored in field conditions. In this study our aim was to validate an ecotoxicologic approach to evaluate both bioaccumulation and toxicologic effects caused by airborne pollutants. Specimens of the land snail Helix aspersa were caged in five sites in the urban area of Ancona, Italy. After 4 weeks, trace metals (cadmium, chromium, copper, iron, manganese, nickel, lead, and zinc) and polycyclic aromatic hydrocarbons (PAH[s) were measured and these data integrated with the analyses of molecular and biochemical responses. Such biomarkers reflected the induction of detoxification pathways or the onset of cellular toxicity caused by pollutants. Biomarkers that correlated with contaminant accumulation included levels of metallothioneins, activity of biotransformation enzymes (ethoxyresorufin O-deethylase, ethoxycoumarin O deethylase), and peroxisomal proliferation. More general responses were investigated as oxidative stress variations, including efficiency of antioxidant defenses (catalase, glutathione reductase, glutathione S-transferases, glutathione peroxidases, and total glutathione) and total oxy-radical scavenging capacity toward peroxyl and hydroxyl radicals, onset of cellular damages (i.e., lysosomal destabilization), and loss of DNA integrity. Results revealed a marked accumulation of metals and PAHs in digestive tissues of organisms maintained in more traffic-congested sites. The contemporary appearance of several alterations confirmed the cellular reactivity of these chemicals with toxicologic effects of potential concern for human health. The overall results of this exploratory study suggest the utility of H. aspersa as a sentinel organism for biomonitoring the biologic impact of atmospheric pollution in urban areas.
This paper evaluated the frequency, magnitude and dose/concentration range of hormesis in four species: The aquatic plant Lemna minor, the micro-alga Pseudokirchneriella subcapitata and the two terrestrial plants Tripleurospermum inodorum and Stellaria media exposed to nine herbicides and one fungicide and binary mixtures thereof. In total 687 dose-response curves were included in the database. The study showed that both the frequency and the magnitude of the hormetic response depended on the endpoint being measured. Dry weight at harvest showed a higher frequency and a larger hormetic response compared to relative growth rates. Evaluating hormesis for relative growth rates for all species showed that 25% to 76% of the curves for each species had treatments above 105% of the control. Fitting the data with a dose-response model including a parameter for hormesis showed that the average growth increase ranged from 9+/-1% to 16+/-16% of the control growth rate, while if measured on a dry weight basis the response increase was 38+/-13% and 43+/-23% for the two terrestrial species. Hormesis was found in >70% of the curves with the herbicides glyphosate and metsulfuron-methyl, and in >50% of the curves for acifluorfen and terbuthylazine. The concentration ranges of the hormetic part of the dose-response curves corresponded well with literature values.
Keywords: Soil Heavy metal Time-of-flight secondary ion mass spectrometry (TOF-SIMS) Field emission scanning electron microscopy (FE-SEM) Energy-dispersive X-ray spectrometer (EDS) a b s t r a c t Relatively new techniques can help in determining the occurrence of mineral species and the distribution of contaminants on soil surfaces such as natural minerals and organic matter. The Bt horizon from an Endoleptic Luvisol was chosen because of its well-known sorption capability. The samples were contaminated with Cu 2+ and/or Pb 2+ and both sorption and desorption experiments were performed. The preferential distribution of the contaminant species (63 Cu and 208 Pb) to the main soil components and their associations were studied together with the effectiveness of the surface sorption and desorption processes. The results obtained were compared with non-contaminated samples as well as with previous results obtained by different analytical techniques and advanced statistical analysis. Pb 2+ competes favorably for the sorption sites in this soil, mainly in oxides and the clay fraction. Cu 2+ and Pb 2+ were mainly associated with hematite, gibbsite, vermiculite and chlorite. This study will serve as a basis for further scientific research on the soil retention of heavy metals. New techniques such as spectroscopic imaging and transmission electron microscopy make it possible to check which soil components retain heavy metals, thereby contributing to propose effective measures for the remediation of contaminated soil.
A single solution reagent is described for the determination of phosphorus in sea water. It consists of an acidified solution of ammonium molybdate containing ascorbic acid and a small amount of antimony. This reagent reacts rapidly with phosphate ion yielding a blue-purple compound which contains antimony and phosphorus in a 1:1 atomic ratio. The complex is very stable and obeys Beer's law up to a phosphate concentration of at least 2 μg/ml.The sensitivity of the procedure is comparable with that of the stannous chloride method. The salt error is less than 1 %.
The presence of metals in municipal sewage sludge is still a major obstacle to their land application. Forest land application of sludge reduces the possibility of metals entering the human food chain. Present knowledge of their long-term behavior in forest soil is however limited. The risk of metals leaching to the aquatic ecosystem situated downstream from treated zone must be evaluated. This paper present a comparison of the risks of water contamination when sludges are applied to forests instead of cropland. The levels of metals in municipal sludge, their form and their mobility in sludge-treated soil are reviewed. Finally, the regulations of the Province of Quebec that have been established to protect forest land are compared to the recommendations of the U.S. Environmental Protection Agency. Although sludge applications to forest land reduce the risk of human food chain contamination, properties of forest soils (low pH, low cation exchange capacity, presence of large continuous pores) could represent an increased hazard of metals leaching to aquatic ecosystems. Metal concentrations in sludge vary considerably depending on the source of the sludge. Metals found in sludge are predominantly associated with the solid phase, while soluble and exchangeable forms generally represent less than 10% of the total metals. Short term studies have revealed that metals tend to accumulate in the upper layers of soil, but few studies have evaluated long-term metal mobility or bioavailability. Many factors can contribute to an increase mobility (pH, oxidation-reduction potential, organic matter decomposition). The risk of aquatic ecosystem contamination by aluminum leached from sludge-treated soils hasn't yet been evaluated. It seems, however, that the risk exists if the soil become more acidic after sludge decomposition. Limits on the amount of metals allowed in sludge have been fixed by many countries. Nevertheless, given the wide variation in the standards used to regulate the allowable content of metal in sludge or sludge-treated soils, disagreement presently exist among regulatory agencies. For example, the maximum cadmium limit allowed in sludge destined to be used as forest fertilizer in Quebec is 15 mg kg-1, whereas it is 85 mg kg-1 in the United States. Different philosophical views on environmental protection (zero tolerance or tolerance of a certain level of metals in soil), as well as the organism chosen when standards are set, are responsible for this inconsistency. Before sewage sludge application to forests becomes a common practice, the associated risks of metals leaching to the aquatic ecosystem must be evaluated. Long-term studies should be undertaken in order to establish safe standards for applying sludge in a forest environment. Such additional efforts will enable good quality sludge to be considered as a usable and valuable resource in forestry.
The surface and subsurface horizons of four different soils - an Ultisol (U), a Fluvent (F), an Inceptisol (I) and a Fluvaquent (Fa) - were treated with an acidic solution of Cd2+ with the aim of establishing their sorption capacity, the distribution of Cd in the different geochemical phases of the soil, and to determine the possible mineralogical changes resulting from the treatment. The Cd fractioning process was carried out by means of a sequential chemical extraction. XDR and FE-SEM/EDS were used to determine the mineralogical composition of all of the horizons before and after the treatment with Cd. The majority of the Cd that was added was not sorbed by the soils, which retained between 10.22% in Fa and 16.09% in F. The horizons with the highest content of Fe, Mn and Al oxides, organic matter and high mineralogical variety in the clay fraction were those that absorbed the most Cd. The percentage of exchangeable Cd was the highest in all of the soil, while the fraction of metal associated with crystalline Fe oxides and the residual fraction were very low. The acid treatment affected the mineralogy of all of the soils, reducing the percentage of the most labile minerals and leading to the formation of amorphous phases capable of sorbing Cd. The images obtained by FE-SEM and EDS confirmed the formation and fixation of Cd gels on muscovite, as well as the formation of Cd(NO3)(2) center dot 4H(2)O in Fa.G.
The soil drainage water chemistry of a mature Scots pine stand was studied following an operational-scale addition of sewage sludge. A 1.33ha experimental area at Monaughty forest, northeast Scotland was treated with 200m3ha−1 of anaerobically digested sewage sludge. Approximately 400kgha−1 of nitrogen (N) and 200kgha−1 of phosphorus (P) were applied in the sludge treatment. The hydrological balance and fluxes of nitrogen and phosphorus in throughfall and soil drainage water (O1, O2 and Bs soil horizons) over the short (3 month) and longer-term (17 month) period after application are compared with untreated areas. Immediate increases in soluble ammonium (NH4) and phosphate (PO4) were apparent within the organic soil horizons and PO4 in the Bs horizons of sludge-treated areas. This observation was attributed to the direct leaching of nutrients contained within the original liquid phase which constituted 95% (by volume) of the sludge. The late autumn application of sludge which contained only small amounts of nitrate (NO3) (
Petrographic, mineralogical and geochemical studies have been carried out on beneficiated coal products from mines and preparation plants in the Santa Catarina Basin, southern Brazil, to investigate the range of characteristics exhibited by the materials and the potential impact of their stockpiling and storage on the environment. The coals contain varying proportions of vitrinite and inertinite macerals, and have vitrinite reflectance values ranging from 0.44 to 1.38%. With the exception of one material blended with peat from an external source, they have relatively high percentages of ash (30–58%) and mineral matter (36–66%). The mineral matter consists mainly of clay minerals (kaolinite, illite and illite/smectite), together with 15–25% quartz, up to 10% feldspar, up to 5% calcite and/or dolomite and up to 5% pyrite, and around 1% anatase and/or rutile. Bassanite is also present in low-temperature ash derived from the coals, mainly derived from interaction of Ca and S associated with the organic matter. Jarosite is formed by pyrite oxidation in coals that have been exposed in stockpiles for extended periods.
The coal (anthracite A) in Douro Coalfield (NW of Portugal) has been exploited for many years and has been mainly used as fuel supply by a thermal power plant. The mining activities inevitably impacted the environment, which includes a large number of coal waste piles emplaced over the old mine sites and adjacent areas of the Douro Coalfield. The disposal of coal mining residues represents significant environmental concerns due to their potential influence on soils and sediments, as well as on the surface and groundwater of the surrounding areas. In the present study, the development of sequential extraction combinedwith various advanced analytical techniques was performed to provide an improved understanding of the complex processes related with
sulfide-rich coal waste oxidation, sequences of mineral formation, and the transport mechanisms of hazardous elements by specific neoformed soluble minerals. The results showed the presence of amorphous iron (oxy-)hydroxides and goethite with various degrees of crystallinity, containing hazardous elements, such as As, Cr, Hg, Mo, Se, Pb, U, and others. Some of the neoformed minerals found in the coal waste material are the same as those commonly associated with coal acid drainage, in which oxidation of sulfides plays an important role. The precipitated neoformed minerals include pickeringite, blödite, and a mixture of epsomite, pickeringite, and hexahydrite. As these sulfates may dissolve after the first rain, they may release above-mentioned elements
into surrounding water bodies.
Hormesis is a widespread phenomenon across occurring many taxa and chemicals, and, at the single species level, issues regarding the application of hormesis to human health and ecological risk assessment are similar. However, interpreting the significance of hormesis for even a single species in an ecological risk assessment can be complicated by competition with other species, predation effects, etc. In addition, ecological risk assessments may involve communities of hundreds or thousands of species as well as a range of ecological processes. Applying hormetic adjustments to threshold effect levels for chemicals derived from sensitivity distributions for a large number of species is impractical. For ecological risks, chemical stressors are frequently of lessor concern than physical stressors (e.g., habitat alteration) or biological stressors (e.g., introduced species), but the relevance of hormesis to non‐chemical stressors is unclear. Although ecological theories such as the intermediate disturbance hypothesis offer some intriguing similarities between chemical hormesis and hormetic‐like responses resulting from physical disturbances, mechanistic explanations are lacking. While further exploration of the relevance of hormesis to ecological risk assessment is desirable, it is unlikely that hormesis is a critical factor in most ecological risk assessments, given the magnitude of other uncertainties inherent in the process.
This paper reports about changes in mobility of hazardous elements contained in coal during combustion at a power plant in Santa Catarina (Brazil) and the environmental impact potential of ashes. Total and mobile element concentrations were determined by digestion and sequential extraction. Comparison of results within the mobile fraction showed that after combustion, oxidizable elements bound to organic matter and sulfides in coal were mostly transformed into elements easily soluble in water or slightly acidic conditions and, hence, most readily bioaccumulative in the environment in ashes, mainly U, Cr, and As. Capacity of ashes as a source of mobile pollutants was quantified by combining sequential extraction and annual production. Just considering the easily soluble fraction, coal ashes could leach up to 839tons of Al, 144tons of Fe, 100tons of Mn, 4.6tons of Zn, 3.1tons of Cr, 1.7tons of As, 1.5tons of Cu, 490kg of U, and 20kg of Pb every year. Bottom ashes are disposed of in landfill sites close to the plant. Fly ashes are recycled as construction material. Diagnostic processes do not consider checking for these highly mobile hazardous elements. Hence, uncontrolled dumping and use of these by-products may pose significant risks to environment and human health.
The competitive adsorption of Cd, Cu, Pb, and Zn from 0.025 M NaClO4 solutions onto four soils with differing chemical properties was investigated with batch adsorption experiments. For two mineral soils, adsorption under acidic conditions (pH 5.0) followed the sequence Pb > Cu > Zn > Cd, which corresponds to the order of increasing pK for the first hydrolysis product (e.g., PbOH+) of the metal ions. In contrast, the order of selectivity for two soils containing 20 to 40 g kg-1 organic C was Pb > Cu > Cd > Zn, suggesting that organic matter (OM) increased Cd retention preferentially over that of Zn. When accompanied by a sizable reduction in cation exchange capacity (CEC), extraction of soil OM markedly reduced adsorption of all four metals. However, only Cd and Cu adsorption were appreciably smaller for a soil that maintained a sizable CEC following OM removal. Lead, and possibly Zn, adsorption by soils with substantial inorganic exchange sites may be unresponsive to organic waste amendments. For Cd and Cu, increased soil OM should restrict mobility and bioavailability, at least under acidic conditions where soluble metal complex formation is limited.
A histochemical staining technique using sodium rhodizonate was developed for detecting lead in living or preserved plant tissues. Sodium rhodizonate formed a bright scarlet-red precipitate with lead at pH 3.0, but showed no significant color responses with other metals. The precipitation of lead by this staining technique was confirmed by detection of lead in the red-stained precipitate with electron microscopy X-ray analysis. This histochemical technique for lead provided rapid, quantifiable, and unambiguous evidence for the accumulation and localization of lead in plant tissues. Soil-borne lead accumulated primarily in the roots, although at high concentrations, lead also accumulated at the ends of transpirational streams, particularly at hydathodes, trichomes, and the termini of xylem streams. Lead deposited from the atmosphere accumulated on the surface of conifer foliage and also appeared in or on cell walls of various internal cells and tissues. Lead concentrations in foliage and the color intensity of the stained deposits in spruce foliage decreased with distance from the lead source and increased with age of needles. No evidence of lead deposition inside cell contents was observed by this stain.
To understand bioaccumulation kinetics of metals within biota inhabiting industrially contaminated soils, toxicokinetic dynamics and subcellular fractionation were carried out with the terrestrial snail Helix aspersa in a long-term (six-month) laboratory experiment. Accumulation and elimination kinetics were determined for Cd, Pb, and Zn in both viscera and foot of snails and were described accurately by one-compartment models. The subcellular fractions were obtained by sequential centrifugations and were analyzed by isolating metal-rich granules, tissue fragments, and cytosolic fractions. Different fractions showed metal-specific binding capacities that might be useful in identifying the biological significance of accumulated metal levels in snails. Cadmium was retrieved mainly from the cytosolic fraction, where it was stored in the long term and not excreted, thus explaining the linear accumulation patterns. Most of the accumulated Pb was found in the granular fraction, and snails appeared able to excrete these concretions, leading to achievement of a steady state in internal Pb body burdens. Significant levels of Pb, however, were retrieved at the end of the depuration phase and retained in the cell debris fraction. Zinc showed affinities for both cytosolic and granular fractions, leading to intermediate uptake and excretion patterns. The dynamics of the different sequestration forms at the subcellular level support the observed kinetics of metal body burdens and, in association with the determination of uptake fluxes, allow precise assessment of metal accumulation in snails.
The effects of environmental factors, such as the nature of paddy soil, the presence of rice plants and weeds and applications of compost and weed-killers, on the behavior, growth and reproduction of the mud snail (Cipangopaludina japonica, an important paddy-soil dweller in Japan) were studied. The types of water-soluble substances in the soil and the softness of the mud make paddy soil a suitable habitat for this snail. The snail avoids soils that bear rice plants and weeds, preferring soils without higher plants. Feeding experiments revealed that the snail consumes a great deal of bacterial materials, such as detritus and sludge compost, suggesting that the sewage sludge produced from wastewater-treatment installations can be decreased by the snail if it is applied to paddy fields as sludge compost.
The use of municipal sewage sludge as a fertiliser could be a more adequate means of disposal of this residue than its transport to the dump. The objective of this experiment was to evaluate the effects of different doses of sludge and sowing a mixture of cocksfoot (Dactylis glomerata) and clover (Trifolium repens) on pasture production, botanical composition of the pasture, forage quality, and changes in soil chemical properties. Treatments applied were: (1) no fertilisation (L0), (2) fertilisation with 26 Mg ha–1 of sewage sludge with no sowing (L40), (3) fertilisation with 26 Mg ha–1 of sewage sludge and sowing with 25 kg of Dactylis glomerata L. cv Artabro (Dg) and 3 kg Trifolium repens cv Huia per hectare and (4) 52 Mg ha–1 of sewage sludge with no herbage sowing (L80). Plots were established in a silvopastoral system with Pinus radiata D. Don at a density of 1666 trees ha–1 (3 2 m). The improvement of soil fertility due to organic fertiliser application and the use of Dactylis glomerata increased the production and quality of pasture as well as reduced the risk of fire and erosion, as grasses dominated shrubs. Fertilisation with sewage sludge in soils of acid origin increased the concentration of copper in the pasture and, if cocksfoot was not sown, the levels of this element exceeded the maximum tolerable dietary levels for sheep. On the other hand, fertilisation also increased the levels of zinc in pasture, but values were not above toxic limits for sheep, horses and cattle.
The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials.
The preferential retention of heavy metals by soils is critical to their availability and mobility through the soils to contaminate groundwater. We examined the competitive adsorption of Cu and Zn by Bt horizon of a Savanna Alfisol from a dilute salt solution under a variety of conditions. Copper and Zinc adsorption from the Cu–Zn binary solution produced a characteristic H-type isotherm for Cu, and a linear isotherm for Zn. The distribution coefficient Kd, which defines the affinity of the metals for the soil adsorbents, was five times greater for Cu than Zn. The adsorption envelope of the metals showed that maximum Cu adsorption occurred at pH 5.5 as against pH 6.8 for Zn adsorption probably reflecting difference in the first hydrolysis constant of the metals. The removal of organic matter from the soil reduced Kd,Cu 40 times as compared to the natural soil, whereas Kd,Zn was reduced by half as compared to the natural soil. Similarly, removing amorphous hydrous oxide by extraction with oxalate solution prior to the introduction of Cu and Zn reduced Kd,Cu 100 times, and Kd,Zn by 20 times as compared to the natural soil, but when both amorphous and crystalline hydrous oxides were removed prior to the introduction of Cu and Zn, the Kd,Cu was on par with the natural soil, whereas Kd,Zn increased by more than two times as compared to the natural soil. It seems that reactions with organic matter and amorphous oxides are the major controls on Cu, whereas Zn might be largely sorbed by cation exchange reaction when in competition with Cu for binding sites in soils. The metal binding sites in the amorphous hydrous oxides and organic matter were more selective for Cu than Zn.
Long-term migration and crop uptake of cadmium (Cd) were investigated in a cultivated field experiment, that had been started 41 years earlier on a structured clay loam. One treatment was supplied biennially with digested sewage sludge and PK-fertilizer, while the control received calcium nitrate and PK-fertilizer. The estimated total Cd supply was ca 153 and 13 mg Cd m−2 in the sludge and control treatments, respectively. In the sludge treatment, 92% of applied Cd was recovered in the topsoil and 7% in the upper 17 cm of the subsoil. The total loss of Cd out of the profile was negligible after 41 years, even though increases in dissolved organic carbon (DOC) concentrations were observed throughout the profile. Thus, macropore transport of Cd, either as Cd2+ or complexed by DOC was apparently not significant. This was attributed to the strong sorption capacity of the arable soil and incorporation of the sludge into the soil matrix, thereby increasing the contact of sludge-borne Cd to soil particles and protecting the Cd from transport in macropores. Cd solubility in equilibrium extracts of Ca(NO3)2 increased by a factor of 20 in the sludge treatment compared to the control. This was reflected in the Cd concentration of the straw fraction in barley, which was almost doubled in the sewage sludge treatment. The grain fraction showed, however, no significant increase in Cd concentration. As crop biomass increased as a consequence of sewage sludge supply, the Cd offtake in harvest was more than twice as high compared to the control. The sewage sludge applications did not pose a high risk for leaching losses of Cd in this soil, but resulted in increased Cd concentrations in the straw fraction.
Three soils, representative of various physico–chemical properties, an acid soil from a granitic arena with a sandy texture, a calcareous soil with a sandy silty texture and a clayey and silty one, were used in a lysimetric experiment to evaluate the ecotoxicological risks associated with the disposal of sewage sludge composts (SSC) containing trace metal contents below the recommended limit values established by the French legislation. A crop of colza (Brassica napus) was grown on the amended soils. Based on the results from this experiment, SSC application enhanced the nutritional levels of the soils and stimulated the growth of plants. Chemical fractionation of composts and amended soils was performed using a sequential extraction technique. The pattern of metal distribution in the five fractions gave a good prediction of the trace metal behaviour in soils. Among the metals studied, Zn was the one that moved most readily in the soils (except in the calcareous soil) since compost application increased the proportion of the most labile forms of Zn and especially its pH 4.7 acid-soluble forms in the amended soils. The migration of Cu and Pb within the profiles of amended soils was significantly influenced by the release of soluble organics from the amended layers during the sludge–soil equilibration period. However, leachates were very little affected by SSC application as metal redistribution took place in deep layers of these amended soils. The movement of Pb within the profiles of the amended soils was not pH dependent whereas the mobility and plant availability of Cu and Zn increased as soil pH decreased. The sequence of trace metal concentrations in all plant parts was: Zn⪢Cu>Pb. Colza leaves were the organs of accumulation of trace metals and nutrients (except Na). Zn contents in leaves were governed by SSC loading rates. Principal component analysis performed on the ‘total’ metal and nutrient concentrations in plants showed on the one hand that no deficiency in nutrients caused by interactions with trace metals arose in the plant organs and on the other hand that the nutrient and trace metal contents in plants were more influenced by soil nature than compost application.
A single solution reagent is described for the determination of phosphorus in sea water. It consists of an acidified solution of ammonium molybdate containing ascorbic acid and a small amount of antimony. This reagent reacts rapidly with phosphate ion yielding a blue-purple compound which contains antimony and phosphorus in a 1:1 atomic ratio. The complex is very stable and obeys Beer's law up to a phosphate concentration of at least 2 μg/ml.The sensitivity of the procedure is comparable with that of the stannous chloride method. The salt error is less than 1 %.RésuméUne méthode spectrophotométrique est décrite pour le dosage du phosphate dans l'eau de mer, an moyen de molybdate d'ammonium, en présence d'acide ascorbique et d'antimoinc. Il se forme rapidement un composé violet bleu, renfermant antimoine et phosphore dans un rapport atomique de 1:1.ZusammenfassungBeschreibung einer Methode zur Bestimmung von Phosphat in Mecrwasser mit Hilfe von Ammoniummolybdat in Gegenwart von Ascorbinsäure und Antimon. Der gebildete blau-violette Komplex wird spektrophotometrisch gemessen.
There is growing public concern in Zimbabwe over the illegal cultivation of vegetables on soils amended with sewage sludge or irrigated with admixtures of sewage and sewage sludge. Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but lead to elevated heavy metal uptake by crops, which may affect food quality and safety. The work reported here studied heavy metal concentrations in crops irrigated with sewage sludge and sewage/sewage sludge admixtures at Firle Municipal Farm in Harare. The crops analysed in this study are heavily contaminated with the four regulated elements: Cd, Cu, Pb and Zn. This contamination is at its highest in two of the staple dietary crops maize and tsunga. Tsunga leaves contained 3.68 mg kg−1 Cd, over 18 times the permissible level by the EU standards (0.2 mg kg−1); Cu concentrations were 111 mg kg−1, 5 times the EU Standard (20 mg kg−1); concentrations of Pb were 6.77 mg kg−1, over 22 times the permissible levels allowed by both EU standards and UK guidelines (0.3 mg kg−1); Zn concentrations were 221 mg kg−1, over 4 times the guideline value (50 mg kg−1). The other plants (beans, maize, peppers and sugarcane) also contained concentrations of heavy metals above the permissible levels. Furthermore, the concentrations observed in this study were higher than those reported by other workers who have examined vegetation from other contaminated sites. This study highlights the potential risks involved in the cultivation and consumption of vegetables on plots irrigated with sewage sludge, a practice which may place at risk the health of the urban population who consume these vegetables.
Biosolids have been widely used for land reclamation, but information on their use in restoration, i.e., on less degraded areas, is scarce. Biosolids may be used to restore forest ecosystems by fostering tree establishment in degraded shrublands. Detailed knowledge on the effects of biosolid application is needed to optimize such practice. We evaluated the effect of different rates (0, 7.5 and 14.5 kg dry weight per plant) and types of biosolid application on the performance of Pinus halepensis and Quercus ilex seedlings, and operational costs. Biosolids increased seedling mortality in both species, particularly when seedlings were planted in direct contact with them. Mortality mostly occurred during the first year, and was probably favored by soil shrinking and salinity. Foliar and needle nitrogen concentration increased with biosolid rate in the short term, but biosolids affected negatively (P. halepensis), or had no effect (Q. ilex) on phosphorus and potassium concentration. Biosolids had a positive effect on P. halepensis growth, and a negative effect on Q. ilex growth at the highest rate when seedlings were in contact with biosolids. Cost of this type of biosolid application approximately doubled plantation cost, but were similar or cheaper that landfill disposal of biosolids. The lowest application rate showed the best balance between seedling response and costs for P. halepensis, whereas biosolid use cannot be recommended for Q. ilex.
Land application of contaminated waste products has been defended as beneficial use by some scientists and regulators, based on the premise that the behavior of any toxins accumulated in soils from this practice is reasonably well understood and will not have detrimental agronomic or environmental impacts into the foreseeable future. In this review, I use the case of toxic metals in sewage sludges applied to agricultural land to illustrate that metal behavior in soils and plant uptake is difficult to generalize because it is strongly dependent on the nature of the metal, sludge, soil properties and crop. Nevertheless, permitted agricultural loadings of toxic metals from sewage sludges are typically regulated using the sole criterion of total metal loading or concentrations in soils. Several critical generalizing assumptions about the behavior of sludge-borne metals in soil-crop systems, built into the US EPA risk assessment for metals, have tended to underestimate risks and are shown not to be well justified by published research. It is argued that, in the absence of a basic understanding of metal behavior in each specific situation, a more precautionary approach to toxic metal additions to soils is warranted.
As an aid to evaluating the environmental threat posed by Cu and Zn when both are present in acid soils, competitive and noncompetitive adsorption of Cu and Zn onto samples of the surface horizon of eight such soils was measured in batch experiments carried out at pH 5 with 0.01 M NaNO3 as background electrolyte. Noncompetitive adsorption of Cu exceeded that of Zn, especially in the soils with greatest organic matter contents. These data were better fitted by the Freundlich equation than by the Langmuir equation, possibly due to the heterogeneity of the adsorbent surfaces. The Langmuir–Freundlich equation was not appropriate for these data: it could not be fitted to the Zn data, and when fitted to the Cu data the uncertainty in the values of its parameters was too large for them to be useful. Total metal adsorption from solutions containing Cu and Zn in 1 : 1 mole ratio was intermediate between adsorption from Zn and Cu solutions of the same total concentration, indicating competition between the two metals. Adsorption of Zn was severely depressed (in some soils almost completely) by the presence of increasing concentrations of Cu in the adsorption solution, but adsorption of Cu was depressed by at most 31% by the presence of increasing concentrations of Zn. Adsorption of Zn from solutions containing both Zn and Cu was modelled well by Murali and Aylmore's generalization of the Freundlich equation, but this equation reduced to the Freundlich equation itself when it was fitted to data for the adsorption of Cu from mixed solutions. Desorption of Cu into NaNO3 solution from previously Cu-loaded soils in no case exceeded 11% of the Cu previously adsorbed, whereas analogous desorption of Zn was in all cases greater and ranged from 9% to 32%. Desorption of both Cu and Zn was greater when Cu was desorbed into Zn(NO3)2 and Zn into Cu(NO3)2.
The availability of the resources is an important factor for high shares of biomass to penetrate the electricity, heat or liquid fuel markets. We have analysed the geographical and technical potential of energy crops for the years 2050–2100 for three land-use categories: abandoned agricultural land, low-productivity land and ‘rest land’, i.e. remaining no-productive land. We envisaged development paths using four scenarios resulting from different future land-use patterns that were developed by the Intergovernmental Panel on Climate Change in its Special Report on Emission Scenarios: A1, A2, B1 and B2. The geographical potential is defined as the product of the available area for energy crops and the corresponding productivity level for energy crops. The geographical potential of abandoned agricultural land is the largest contributor. For the year 2050 the geographical potential of abandoned land ranges from about 130 to 410 EJ yr−1. For the year 2100 it ranges from 240 to 850 EJ yr−1. The potential of low-productive land is negligible compared to the other categories. The rest land area is assumed to be partly available, resulting in ranges of the geographical potential from about 35 to 245 EJ yr−1 for the year 2050 and from about 35 to 265 EJ yr−1 in 2100. At a regional level, significant potentials are found in the Former USSR, East Asia and South America. The geographical potential can be converted to transportation fuels or electricity resulting in ranges of the technical potential for fuels in the year 2050 and 2100 equal to several times the present oil consumption.
Open cast mining has a strong impact on the environment, the intensity depending on the morphology of the deposit and on the nature of the minerals. At Touro mine (NW Spain) there is a large area covered by tailings, one of which, called the "sedimentation bank", was used to deposit sludge resulting from the extraction of copper in the flotation plant. Three zones were selected and the soils were sampled to analyse the changes brought about by vegetation on the chemical and mineralogical properties of the soils developed over the sedimentation bank and its development over time. The vegetation increased the pH, contents of organic material, nitrogen, clay and free oxides of Fe and Al, and the cationic exchange capacity of the soils. The decrease in the sulphide content, benefited by the vegetation process, led to a reduction in the total content of Cr and Cu. The vegetation also contributed towards the alteration of the primary minerals. The transformation of jarosite, the formation of nanocrystals of hematite, goethite, hydroxypolymers, and amorphous minerals that contained Cu, Cr and Pb were observed. Nevertheless the high Cu and Cr contents indicate that it is advisable to change the restoration process.
Linear Mixed-Effects * Theory and Computational Methods for LME Models * Structure of Grouped Data * Fitting LME Models * Extending the Basic LME Model * Nonlinear Mixed-Effects * Theory and Computational Methods for NLME Models * Fitting NLME Models
Fenton's reaction is proposed as an accelerated weathering test for sulphides associated with Brazilian Coal Mining Residues (CMR), that are exposed to oxygen and water during the mining of coal. TEM and SEM/EDX were used to evaluate the nature, occurrence and distribution of minerals in remaining coals and other lithological units, before and after applying the test. Oxidation of CMRs was examined by analyzing soluble sulphur (sulphate) and dissolved metals by ICP-MS or ICP OES. As dissolved sulphate increases, dissolved Zn, Cd, Cu and Co concentrations increase, leading to undetectable amounts in the remaining solid phases; dissolved Ni and Mn also increase with the mobilized sulphur, but the remainder in the solids is the most important fraction; Fe and Pb are not mobilized due to precipitation as jarosite or hematite in the case of Fe or as sulphate in the case of Pb. Agreement between the observed results and the predictions by geochemical modelling is discussed.
The geochemical characteristics of coal cleaning rejects (CCR) in Santa Catarina State, Brazil, were investigated. Around 3.5 million ton/year of coal waste are dumped in Santa Catarina State. Coal beneficiation by froth flotation results in large amounts of CCR composed of coaly and mineral matter, the latter characterised by the occurrence of sulphide minerals and a broad array of leachable elements. The total and leachable contents of more than 60 elements were analysed. Atmospheric exposure promotes sulphide oxidation that releases substantial sulphate loads as well as Ca2+, K+, Mg2+, Cl- and Al3+. The metals with the most severe discharges were Zn, Cu, Mn, Co, Ni and Cd. Most trace pollutants in the CCR displayed a marked pH-dependent solubility, being immobile in near-neutral samples. The results highlight the complex interactions among mineral matter solubility, pH and the leaching of potentially hazardous elements.
The concentrations and loadings of major and trace elements in coal mine drainage (CMD) from 49 abandoned mines located in the coal fields of the Brazilian state of Santa Catarina were determined. The CMD sites typically displayed a wide spatial and temporal variability in physical and geochemical conditions. The results of our CMD analyses in Santa Catarina State were used to illustrate that the geochemical processes in the rock piles can be deduced from multiple data sets. The observed relationship between the pH and constituent concentrations were attributed to (1) dilution of acidic water by near-neutral or alkaline groundwater and (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals. The preliminary results of the CMD analyses and environmental health in the Santa Catarina region, Brazil, are discussed.