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A Review of Approaches and Techniques Used in Aquatic Contaminated Sediments: Metal Removal and Stabilization by Chemical and Biotechnological Processes
Abstract
The contamination of aquatic sediments with metals is a widespread environmental problem. Coastal aquatic ecosystems with low hydrodynamics need to be periodically dredged in order to maintain the navigation depth and facilitate sailing; consequently large volumes of contaminated sediments need to be managed. Conventional remediation strategies include in-place sediment remediation strategies (e.g. in situ-capping) and relocation actions; in particular, landfill disposal and dumping at sea are still widely applied. Both this options are becoming unsustainable, due to problems associated with contaminant transport pathways, the uncertainties about long-term stability under various environmental conditions, the limited space capacity, costs and environmental compatibility. Alternative approaches have received increased attention; treatment and reuse of contaminated sediments is politically encouraged, but its application is still very limited. Because of the potential human health and environmental impacts of contaminated sediment, different chemical treatments are conventionally applied for contaminated sediments before reuse in other environmental settings. Environmentally friendly techniques developed for soils and other environmental matrices have been investigated for applications with sediments. Biotechnological approaches are gaining increasing prominence in this field and they are often considered as a promising strategy for the eventual treatment of contaminated sediments. In this paper an overview of the main treatment strategies potentially available for sediment contaminated with metals is given, together with a brief overview of the issue associated with the problem of the sediment management.
... In light of this, an environmentally friendly means of controlling eutrophication in lakes has emerged: sediment dredging [4]. Dredging is a common technique for managing eutrophication problems [5], which aims to reduce the level of eutrophic substances and promote self-2 purification by removing silt and sediment from the bottom of water bodies. The purpose of environmental dredging is to reduce potential risks to human health and the environment; unfortunately, it remains unclear whether environmental dredging alone is effective in reducing such risks [6]. ...
... Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 9 January 2024 doi:10.20944/preprints202401.0659.v15 ...
Dredging is a common technique for managing eutrophication problems in waters, reducing the accumulation of pollutants by removing sediments from the bottom of water bodies. However, dredging can cause complex impacts on lake ecosystems, and it is crucial to understand benefits and mechanisms for environments. In this paper, the dredged and undredged areas in the Caohai portion of Dianchi Lake were studied to analyze the effects of dredging on nitrogen-phosphorus transport and conversion and changes in nitrogen-phosphorus morphology content and its mechanisms by comparing the nitrogen-phosphorus morphology content, percentage; nitro-gen-phosphorus ratio, and release contribution of the two areas. It was found that the ratio of sta-bilized nitrogen (SN) to stabilized phosphorus (SP) in the dredged area was lower than that in the non-dredged area; the BD-P and TOC contents had a large turnaround at the 16-20 cm position of the sediment in the dredged area; and the main conclusions were that the dredging would disrupt the internal equilibrium of the lake system for many years, and in particular, it would have the greatest effect on the balance of the BD-P in the phosphorus forms of the sediment, and that the column cores of the dredged area from 0 to 16 cm might be newly accumulated sediments after the dredging project. However, with time, the distribution of nitrogen and phosphorus forms in the newly accumulated sediments will gradually reach a new equilibrium. In addition, dredging will also cause significant changes in the retention efficiency of nitrogen and phosphorus in the sediment, and the stable nitrogen and phosphorus forms will be released and transformed into unstable ni-trogen and phosphorus forms.
... Sediment contamination is of the most concerning environmental issues worldwide that requires close attention not only towards its evaluation but also towards its remedial measures (Sparrevik et al. 2011;Akcil et al. 2015). Conventional techniques such as situ capping, landfill disposal, and sea dumping could be utilized keeping in consideration towards their effectiveness is not long term . ...
... Conventional techniques such as situ capping, landfill disposal, and sea dumping could be utilized keeping in consideration towards their effectiveness is not long term . Advanced biological treatment, thermal treatment, and in situ chemical treatment could be taken into consideration as these method are efficient and reliable for remediation of coastal sediments (Akcil et al. 2015). ...
The provenance, paleoweathering and paleoredox conditions of sandstones of the Vryheid Formation of the Ecca Group in the Highveld Coalfield, Mpumalanga, South Africa, were studied with the intention of identifying possible detrital source rocks. The investigation approach involved collecting sandstone samples from borehole cores, followed by laboratory studies of mineralogy and petrography and major and trace element analysis by X-ray fluorescence (XRF). Mineralogy and petrographic analyses indicate that these sandstones are arkosic to subarkosic arenites. The generalized mineralogical compositions, in order of abundance, consist of monocrystalline and polycrystalline quartz, plagioclase, igneous and volcanic rock fragments and minor to trace amounts of mudstone clasts. Quartz grains are predominantly monocrystalline, implying that they came from granitic and volcanic rocks as well as hydrothermal quartz veins. The presence of higher amounts of feldspars favors either a fast/high depositional rate or a relatively dry or cold climate in the source area and is also indicative of the dominance of felsic igneous or metamorphic rocks in the source area. The bulk rock geochemistry supports the petrographic results. The ratio of K2O/Na2O and the plots of Na2O-CaO-K2O and Th-Sc-Zr/10 attest to a passive margin tectonic setting. The observed patterns of REE values, ratios of K2O/Al2O3, Al2O3/TiO2, La/Sc, Th/Sc, Th/Co, and Th/Cr, plots of Th/Co vs La/Sc, Hf vs La/Th, Th vs Sc, V-Ni-Th and discriminant function further suggest felsic rock sources. The sediments were deposited by glacial material and underwent mechanical weathering and grinding; therefore, the sediments deviate from normal chemical weathering trends. The chemical index of alteration (CIA) suggests minimal chemically weathered source rocks typically deposited under a cool to temperate climate. U contents and authigenic U, V/Cr, Ni/Cu and Cu/Zn ratios attest to an oxidic depositional environment.
... Microbial types such as archaea, bacteria, cyanobacteria, and fungus might be employed to HM in sediment and soils (Xu et al., 2022). The commonly employed bioleaching microbes are Acidithiobacillus, Leptospirillum, Sulfobacillus, Ferrimicrobium, Sulfurisphaera (Akcil et al., 2015;Vera et al., 2013), bio accumulators like Pseudomonas putida, Bacillus subtilis, Bacillus cereus, Aspergillus niger, and Saccharomyces cerevisiae (Mir-Tutusaus et al., 2018;Mishra & Malik, 2013) and bio-sorbers like Aspergillus flavus, and Sterigmatomyces halophilus are primarily employed (Bano et al., 2018). In addition, electrochemical analysis, ICP-MS, atomic absorption spectroscopy (AAS), and optical detection have been used to monitor HM ions, with ICP-MS and AAS serving as the principal detection methods. ...
Metals and metalloids tainting sediments is an eminent issue, predominantly in megacities like Mumbai and Navi Mumbai, requiring an exhaustive examination to identify metal levels in river bodies that serve various populations. Thus, utilising pollution indices, multivariate analysis, and health risk assessment studies, we propose a novel investigation to examine the metal content in the Ulhas River sediments, a prominent agricultural and drinking water supply (320 million-litre per day) near Mumbai in Maharashtra, India. The eleven metals and metalloids (As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) were examined monthly from 10 stations totaling 120 sediment specimens from October 2022 to September 2023. Investigations revealed that average values of Cr, Cu, Hg, and Ni exceeded Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council values, while all metals exceeded World surface rock average limits except As. Various pollution indices showed that upstream sites had none to low level contamination, whereas downstream locations had moderate to considerable contamination, suggesting anthropogenic influences. Furthermore, multivariate analysis including correlation, cluster, and principal component analysis identified that sediment pollution was mostly caused by anthropogenic activities. Lastly, health risk assessment indicated Fe was non-carcinogenic to children, whereas Cr and Ni were carcinogenic to children and adults, with children being more susceptible. Thus, from the findings of the study it is clear that, despite low to moderate pollution levels, metals may have significant repercussions, thus requiring long-term planning, frequent monitoring, and metal abatement strategies to mitigate river contamination.
... 13 In addition, by the complex nature, some heavy metals form complexes, and the relative toxicity of these complexes is extremely high as compared to the heavy metals. 14 However, due to the high risks associated with the toxicity of heavy metals, vegetables that have been polluted with them through anthropogenic or natural sources are extremely important. About 90% of the total amount of heavy metals that humans ingest comes from vegetables, with the other 10% coming via contaminated dust and skin contact. ...
... Conventional approaches to managing these sediments involve landfilling and confined or unconfined disposal in the ocean. Nonetheless, these methods have numerous drawbacks, including high costs, limited capacity, and the potential for environmental contamination [3,4]. Given the substantial quantities of sediments, alternative solutions should be explored to dispose of dredged materials properly. ...
Treating dredged sediment is a complex processing and ongoing challenge. To utilize dredged sediment for the landfill or construction purposes, a material fabricated from a mixture of dredged sediment, Portland cement, and fly ash, was cured under room temperature and hydrothermal condition at 180 °C and 0.9 MPa pressure for 16 hours. The response surface methodology was used to evaluate the compressive strength of the material, with the range of factors investigated being the dredged sediments/solid ratio (0.3-0.9), cement/fly ash ratio (2-4), and water/solid ratio (0.45-0.55). The fitting models offered an accurate and reliable match to the actual data. The optimum mix proportions of two curing conditions were obtained using total desirability function, meet multi-objective criteria. This result finger out hydrothermal curing significantly enhances treatment capacity of dredged sediment, with a lower CO2 emission in the mixture compared to ambient curing. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to figure out the difference between the minerals formed in the material under two curing conditions, such as tobermorite.
... In the bioremediation field, researchers have studied environmentally friendly, economically viable and socially acceptable techniques to remove contaminants from the environment [39][40][41]. In particular, many microorganism enzymes are isolated, purified or partially purified to catalyze the detoxification of contaminants, and these techniques are becoming important because [42] free enzyme bioremediation is not dependent upon the growth of intact organisms; hence, the rate of detoxification is directly linked to the catalytic properties and concentration of applied enzymes [43]. ...
A single strain of yeast was isolated from industrial gluten bread (GB) purchased from a local supermarket. This strain is responsible for spoilage consisting of white powdery and filamentous colonies due to the fragmentation of hyphae into short lengths (dust-type spots), similar to the spoilage produced by chalk yeasts such as Hyphopichia burtonii, Wickerhamomyces anomalus and Saccharomycopsis fibuligera. The isolated strains were identified initially by traditional methods as Wickerhamomyces anomalus, but with genomic analysis, they were definitively identified as Cyberlindnera fabianii, a rare ascomycetous opportunistic yeast species with low virulence attributes, uncommonly implicated in bread spoilage. However, these results demonstrate that this strain is phenotypically similar to Wi. anomalus. Cy. fabianii grew in GB because of its physicochemical characteristics which included pH 5.34, Aw 0.97 and a moisture of about 50.36. This spoilage was also confirmed by the presence of various compounds typical of yeasts, derived from sugar fermentation and amino acid degradation. These compounds included alcohols (ethanol, 1-propanol, isobutyl alcohol, isoamyl alcohol and n-amyl alcohol), organic acids (acetic and pentanoic acids) and esters (Ethylacetate, n-propil acetate, Ethylbutirrate, Isoamylacetate and Ethylpentanoate), identified in higher concentrations in the spoiled samples than in the unspoiled samples. The concentration of acetic acid was lower only in the spoiled samples, but this effect may be due to the consumption of this compound to produce acetate esters, which predominate in the spoiled samples.
... Bioremediation is one of the processes that uses various microbes such as bacteria, fungi, algae, and higher plants to treat heavy metal pollution [32]. Bioremediation tools are used to convert toxic heavy metals into their less toxic form [33][34][35]. The presence of excessive heavy metals in the environment causes microorganisms to evolve several mechanisms such as adsorption, chemical reduction, and complexation to survive in a polluted environment and to clean up the polluted environment [36][37]. ...
Contemporary apprehensions about environmental degradation stem from various natural and anthropogenic activities, encompassing rapid industrialization, global economic expansion, increased agrochemical use, and increased hydrocarbon deposition. This multifaceted array of activities contributes to environmental decay, resulting in decreased crop yields and deleterious effects on the biota. Heavy metals emerge as prominent contaminants in environmental pollution, characterized by their nonbiodegradable nature and prolonged persistence in ecosystems. The deleterious repercussions of heavy metal contamination on soil and aquatic organisms are multiple, thereby necessitating vigilant consideration. The adverse consequences of heavy metal exposure extend beyond the environmental impact to include significant implications for human health. Consequently, remedial interventions become imperative to eliminate hazardous organic heavy metals or facilitate their conversion into less harmful inorganic forms. This review synthesizes the existing literature on the intricate interplay between anthropogenic activities, heavy metal contamination, and the resulting environmental and health implications. By scrutinizing these intricate dynamics, this review seeks to illuminate the imperatives of effective remediation strategies in mitigating the adverse consequences of heavy metal pollution, thus fostering sustainable environmental practices and protecting public health.
... is the process of disinfecting up and extracting pollutants or contaminants from the environment using living organisms such as bacteria, fungi, or an environmentally beneficial and long-term technique (Akcil et al., 2015). Organic ents) and inorganic substances (e.g., heavy (Department of Chemistry1 , Jiwaji Water is one of the most important and valuable assets on the planet, sustaining life and maintaining ecosystems. ...
Biotechnology is one of the emerging fields that can add new and better application in a wide range of sectors like health care, service sector, agriculture, and processing industry to name some. This book will provide an excellent opportunity to focus on recent developments in the frontier areas of Biotechnology and establish new collaborations in these areas. The book will highlight multidisciplinary perspectives to interested biotechnologists, microbiologists, pharmaceutical experts, bioprocess engineers, agronomists, medical professionals, sustainability researchers and academicians. This technical publication will provide a platform for potential knowledge exhibition on recent trends, theories and practices in the field of Biotechnology
... To summarize, the Cr content levels dictate that further investigations may be necessary before sediments can be repurposed and Cu and Zn levels could have potential negative environmental effects (GEODE 2016). It is necessary to either employ a valorization method that immobilizes pollutants within a matrix or examine the need for a decontamination process to avoid the potential solubility and migration of pollutants, and their effects on the environment (Akcil et al. 2015, Couvidat et al. 2016. ...
In this study, we investigated the siltation rate, evolution, and spatial distribution of sediments within the Siliana Dam reservoir, north-west Tunisia. We analyzed the geotechnical, chemical, mineralogical, and trace metal content properties of sediment samples collected from the reservoir. Additionally, we examined the potential valorization of reservoir sediments in road construction and the effects of hydrated lime treatment on their bearing characteristics. The Siliana dam reservoir is currently 50% silted up, and the sedimentation rate is approximately 1.52% per year. The sediments are mainly fine-grained, low organic with medium to high plasticity and high content of calcium carbonate. The sediments consist of calcite and quartz, with minor amounts of dolomite, hematite, and phyllosilicate minerals. Chromium, zinc, and copper contents in the sediments exceed environmental standards. The lime treatment improved the materials bearing capacity. Adding lime (5% by weight) resulted in an immediate bearing ratio of 26%, a higher ratio compared to the raw sediments. The study of the spatial and temporal evolution of sediment accumulation provides information to develop strategies for mitigating the accumulation of sediments. The sediment characterization evaluated the suitability of sediments to be used as construction materials, offering potential cost savings and contributing to informed decision-making for reservoir management.
... The wind dispersal of toxic trace elements from mine tailings in arid and semiarid environments is a globally recognized concern which requires attention to minimize the risk of biomagnification of these elements into the food chain [1]. Conventional techniques used for the remediation of contaminated soils are not eco-friendly and are expensive and energy intensive [2,3]. The use of cost-effective remediation strategies involving the use of plants and the associated microbial communities to restore the ecosystem services of contaminated and/or degraded areas has emerged as a highly promising approach in recent decades [4,5]. ...
The implementation of phytoremediation strategies under arid and semiarid climates requires the use of appropriate plant species capable of withstanding multiple abiotic stresses. In this study, we assessed the combined effects of organo-mineral amendments and microbial inoculants on the chemical and biological properties of mine tailings, as well as on the growth of native plant species under drought stress conditions. Plants were cultivated in pots containing 1 kg of a mixture of mine tailings and topsoil (i.e., pre-mined superficial soil) in a 60:40 ratio, 6% marble sludge, and 10% sheep manure. Moreover, a consortium of four drought-resistant plant growth-promoting rhizobacteria (PGPR) was inoculated. Three irrigation levels were applied: well-watered, moderate water deficit, and severe water deficit, corresponding to 80%, 45%, and 30% of field capacity, respectively. The addition of topsoil and organo-mineral amendments to mine tailings significantly improved their chemical and biological properties, which were further enhanced by bacterial inoculation and plants’ establishment. Water stress negatively impacted enzymatic activities in amended tailings, resulting in a significant decrease in acid and alkaline phosphatases, urease, and dehydrogenase activities. Similar results were obtained for bacteria, fungi, and actinomycete abundance. PGPR inoculation positively influenced the availability of phosphorus, total nitrogen, and organic carbon, while it increased alkaline phosphatase, urease (by about 10%), and dehydrogenase activity (by 50%). The rhizosphere of Peganum harmala showed the highest enzymatic activity and number of culturable microorganisms, especially in inoculated treatments. Severe water deficit negatively affected plant growth, leading to a 40% reduction in the shoot biomass of both Atriplex halimus and Pennisetum setaceum compared to well-watered plants. P. harmala showed greater tolerance to water stress, evidenced by lower decreases observed in root and shoot length and dry weight compared to well-watered plants. The use of bioinoculants mitigated the negative effects of drought on P. harmala shoot biomass, resulting in an increase of up to 75% in the aerial biomass in plants exposed to severe water deficit. In conclusion, the results suggest that the combination of organo-mineral amendments, PGPR inoculation, and P. harmala represents a promising approach to enhance the phytoremediation of metal-polluted soils under semiarid conditions.
... Cumulative tendency in the biomass of the food chain poses a serious threat to plants, animals and humans even when exposed to low concentrations (Bolan et al., 2014;Sarwar et al., 2017). In-situ restoration approaches of pollutants are mostly ecologically friendly and costeffective (Akcil et al., 2015). Removing these TMs from agricultural soil to limit their effect on the quality of farming products is therefore essential to maintaining a safe food chain and a healthy agricultural ecosystem. ...
An in situ pot experiment was carried out in a net house to study the combined effect of a mixture of microbial inoculants at different levels of 0, 1, 1.5, 2, 2.5, and 3 g/kg in dry soil with Limnocharis flava (L.) Buchenau plants grown on agricultural land contaminated with lead (Pb) and cadmium (Cd). The results showed that plant growth, fresh inflorescence yields and accumulation of Pb and Cd in L. flava plant parts gradually increased with increasing levels of the applied microbial inoculants in the contaminated soil. The highest total content of Pb and Cd was determined in roots (6.63–32.46 and 0.12–0.72 mg/kg dw), followed by stems and leaves (1.20–3.08 and 0.04–0.09 mg/kg dw) and inflorescence parts (0.012–0.120 and 0.011–0.065 mg/kg fw). The application of microbial inoculants in the range of 2–2.5 g/kg dry soil stimulated the growth and fresh inflorescence yields of L. flava, increased the accumulation of Pb and Cd in inedible parts, ensuring safety for edible parts of L. flava plants in accordance with QCVN8-2:2011/BYT and FAO/WHO regulations. The results of the present work indicate that the flexibility of Pb and Cd can be increased when soil is mixed with microbial inoculants. Long term ex situ experiments are needed to investigate the impact of microbial inoculants mixed with biochar, minerals and nanomaterial for phytomanagement of soil contaminated with multiple metals.
... These sediments are generally regarded as solid waste with high moisture content, complex components (as contaminants), high organic matter content, high compressibility, and low mechanical strength (Xu et al., 2020a(Xu et al., , 2020b. Traditional management of sediments as ocean dumping, land deposit, and blow-filled piling, is not environmentally friendly, unsustainable and uneconomical (Agius and Porebski, 2008;Akcil et al., 2015). Therefore, scholars have been developing new methods to dispose of these sediments to achieve 'waste control by waste' for many years. ...
... Dredging is a common technique for managing eutrophication problems [4], which aims to reduce the level of eutrophic substances and promote self-purification by removing silt and sediment from the bottom of water bodies. The purpose of environmental dredging is to reduce potential risks to human health and the environment; unfortunately, it remains unclear whether environmental dredging alone is effective in reducing such risks [5]. ...
Dredging is a common technique for managing eutrophication problems in waters, reducing the accumulation of pollutants by removing sediments from the bottom of water bodies. However, dredging can have complex impacts on lake ecosystems, and it is crucial to understand its benefits and mechanisms for the environment. In this paper, the dredged and undredged areas in the Caohai portion of Dianchi Lake were studied to analyze the effects of dredging on nitrogen–phosphorus transport and conversion and changes in nitrogen–phosphorus morphology content and its mechanisms by comparing the nitrogen–phosphorus morphology content and percentage, the nitrogen–phosphorus ratio, and the release contribution of the two areas. It was found that the ratio of stabilized nitrogen (SN) to stabilized phosphorus (SP) in the dredged area was lower than that in the undredged area and the BD-P and TOC content had a large turnaround at the 16–20 cm position of the sediment in the dredged area. The main conclusions were that the dredging would disrupt the internal equilibrium of the lake system for many years, with the greatest effect on the balance of the BD-P in the phosphorus forms of the sediment, and that the column cores of the dredged area at 0 to 16 cm might be newly accumulated sediments after the dredging project. However, with time, the distribution of nitrogen and phosphorus forms in the newly accumulated sediments will gradually reach a new equilibrium. In addition, dredging will also cause significant changes in the retention efficiency of nitrogen and phosphorus in the sediment, and the stable nitrogen and phosphorus forms will be released and transformed into unstable nitrogen and phosphorus forms.
... Bioremediation -set of soil and water purifi cation methods based on the use of the biochemical or metabolic potential of microorganisms (bacteria, fungi), algae, and higher plants.The undoubted advantages of this method are effi ciency, cost-eff ectiveness, environmental safety and the absence of secondary pollution [3,4]. Bioremediation using microorganisms has received much attention due to their good effi ciency and use in converting toxic heavy metals into a less harmful form [5]. ...
In Central Asia, there are several storage sites for radioactive waste, which can be called environmental “hot spots” due to their negative impact on the environment, public health and the high risk of destruction of storage facilities during possible natural and technogenic disasters. Such “hot spots” of particular concern include Mailuu-Suu, Min-Kush and Kazhi-Sai in Kyrgyzstan, Charkesar in Uzbekistan, Taboshar and Degmay in Tajikistan. In such ecologically unfavorable zones, toxic elements (radionuclides and other heavy metals) exceed the maximum permissible concentration by tens and hundreds of times [1].
... The wind dispersion of toxic trace elements from mine tailings in arid and semi-arid environments is a globally recognized concern which requires attention to minimize the risk of biomagnification of these elements into food chain [1]. Conventional techniques used for the remediation of contaminated soils are not eco-friendly and are expensive, and energy intensive [2,3]. Therefore, the use of cost-effective remediation strategies involving the use of plants and the associated microbial communities to restore the ecosystem services of contaminated and/or degraded areas has emerged as a highly promising approach in the last decades [4,5]. ...
The implementation of phytoremediation strategies under arid and semi-arid climate requires the use of appropriate plant species capable of withstanding multiple abiotic stresses. In this study, we assessed the combined effects of organo-mineral amendments and microbial inoculants on chemical and biological properties of mine tailings, as well as on growth of native plant species under drought stress conditions. Plants were cultivated in pots containing 1 kg of a mixture of mine tailings and topsoil (i.e. pre-mined superficial soil) in a 60:40 ratio, 6% marble sludge and 10% sheep manure. Moreover, a consortium of four drought-resistant rhizobacteria was inoculated. Three irrigation levels were applied: well-watered, moderate water deficit, and severe water deficit, corresponding to 80%, 45%, and 30% of field capacity, respectively. The addition of topsoil and organo-mineral amendments to mine tailings significantly improved their chemical and biological properties, which were further enhanced by bacterial inoculation and plants’ establishment. Water stress negatively impacted enzymatic activities in amended tailings, resulting in a significant decrease of acid and alkaline phosphatases, urease, and dehydrogenase activities. Similar results were obtained for bacteria, fungi and actinomycetes abundance. PGPR inoculation positively influenced the availability of phosphorus, total nitrogen, and organic carbon, while increased alkaline phosphatase, urease (by about 10%) and dehydrogenase activities (by 50%). The rhizosphere of P. harmala showed the highest enzymatic activity and number of culturable microorganisms, especially in inoculated treatments. Severe water deficit has nega-tively affected plant growth, leading to a 40% reduction in shoot biomass of both Atriplex halimus and Pennisetum setaceum compared to well-watered plants. Peganum harmala showed greater tolerance to water stress, as corroborated by the lower decreases observed in root and shoot length and dry weight compared to well-watered plants. The use of bioinoculants mitigated the negative effects of drought on P. harmala shoot biomass, resulting in an increase of up to 75% in the aerial biomass in plants exposed to severe water deficit. In conclusion, the results suggest that the combination of organo-mineral amendments, PGPR inoculation and P. harmala represents a promising approach to enhance the phytoremediation of metal-polluted soils under semi-arid conditions.
... The level of contamination and existing legislation are determining factors for the choice of management option (Casper 2008;Norén, et al. 2020). Internationally, the most common sediment management methods are disposal at a landfill or in the sea (Akcil, et al. 2015;Bortone, et al. 2004). In the EU, legislation changes imposed more restrictions on landfilling materials such as soil and sediment, and as a consequence, landfilling costs are increasing (European Environment Agency, 2009). ...
Stabilization and solidification (S/S) is known to improve the structural properties of sediment and reduce contaminant mobility, enabling the utilization of dredged contaminated sediment. Further reduction of contaminants (e.g., tributyltin (TBT) and metals) can be done using electrochemical treatment prior to S/S and could potentially minimize contaminant leaching. This is the first study on how electrochemical pretreatment affects the strength and leaching properties of stabilized sediments. It also investigates how salinity and organic carbon in the curing liquid affect the stabilized sediment.
The results showed that the electrolysis reduced the content of TBT by 22% and zinc by 44% in the sediment. The electrolyzed stabilized samples met the requirements for compression strength and had a reduced surface leaching of zinc. Curing in saline water was beneficial for strength development and reduced the leaching of TBT compared to curing in fresh water. The results indicate that pretreatment prior to stabilization could be beneficial in reducing contaminant leaching and recovering metals from the sediment. The conclusion is that a better understanding of the changes in the sediment caused by electrochemical treatment and how these changes interact with stabilization reactions is needed. In addition, it is recommended to investigate the strength and leaching behavior in environments similar to the intended in situ conditions.
... Además, la extracción de metales de los sedimentos contaminados es una oportunidad para recuperar material valioso y fomentar el concepto de economía circular. Aunque se han utilizado varios procesos de separación física para limpiar sedimentos contaminados, principalmente el cribado, la flotación, las extracciones asistidas por ultrasonidos o los hidrociclones, la extracción magnética no se ha aplicado con éxito hasta ahora (Akcil et al., 2015). Sin embargo, este enfoque se ha probado con eficacia en la remediación de suelos (Baragaño et al., 2021). ...
Metal(oid)es como el arsénico, cadmio, cobre, plomo y zinc, pueden suponer una amenaza medioambiental al presentarse en sedimentos marinos. Sin embargo, estos elementos también tienen valor económico, lo que ha generado un interés en su recuperación mediante el empleo de técnicas físico-químicas, aunque la separación magnética no ha sido empleada hasta ahora. En este trabajo, se aplicó la separación magnética de alta intensidad de campo en vía húmeda (WHIMS) para recuperar los metal(oid)es de sedimentos contaminados recogidos en el estuario de Avilés en el norte de España. Una muestra fue analizada mediante tamizado húmedo y análisis ICP-MS, mostrando que el 62% del material se corresponde con la fracción granulométrica 125-500µm, con concentraciones inferiores a las observadas en la fracción <125µm, la más contaminada. Después, se trataron las dos fracciones granulométricas a diferentes intensidades, obteniéndose excelentes resultados de recuperación elemental, especialmente para la granulometría más gruesa. El análisis microscópico indicó que la separación concentró partículas enriquecidas con metal(oid)es y hierro en un volumen reducido de sedimento. Estos resultados sugieren que la separación magnética es una opción viable para la recuperación de metal(oid)es de sedimentos contaminados, brindando un doble beneficio: la restauración de la zona costera y la recuperación de materiales valiosos.
... There was a gradual reduction in Cr(VI) toxicity on phosphate amendment at each increasing concentration of P amendment (Sayantan & Shardendu 2013). The enrichment of PO43above 1 mM did, however, cause a growth reduction in Bacillus licheniformis DAS1, demonstrating the toxicity of phosphate (Akcil et al. 2015, Tripti & Shardendu 2016. ...
The current study is about detoxifying soil and water contaminated with toxic Cr(VI). To ensure that DAS1 could develop as well as possible, the pH was changed between 4 and 10. DAS1 showed its highest growth at pH 8, and at the same pH, it had an 85% potential to remediate by converting Cr(VI) to Cr(III). Immobilized bacteria increased the reduction of Cr(VI) to Cr(III) from the culture medium to 90.4%. The impact of glucose concentrations between 0.5 and 2.5 g.L-1 was examined. The greatest development was seen at pH 8 and 2 g.L-1 glucose concentration. The remediation potential was improved by up to 96% when the growing medium contained 200 mg.L-1 Cr(VI). The value of ks (0.434 g.L-1) demonstrated the substrate’s affinity for bacteria in accordance with the Monod equation, while μ max (0.090 h) demonstrated that DAS1 required 11.11 h for maximal growth. The multifactor experimental design was used to analyze mixed cultures of DAS1 and DAS2 in a 1:1 ratio, and it was determined that the X3Y2Z1 experiment design was best for completely removing Cr(VI) from the growing medium. By making pores using Na2EDTA, it was determined that the cell membrane’s impermeability did not cause Cr(VI) resistance in DAS1. The delayed lag phase indicated that the enzyme activity was inductive rather than constitutive.
... Various conventional chemical processes for the degradation of these toxic substances have been explored to overcome these threats. However, they are insufficient for large-scale commercial administration (Deshmukh et al. 2016;Akcil et al. 2015;Sonawane et al. 2022). Bioremediation is a biological degradation mechanism (by microbes, plants, and microbial or plant secretions) to degrade environmental pollutants. ...
The fungi grow in diverse habitats and potentially secrete an array of extracellular enzymes capable of decomposing matter. The fungal enzymes include amylases, cellulases, catalases, cytochrome P450s, dehalogenases, dehydrogenases, hydrolases, laccases, lipases, peroxidases, proteases, and xylanases; they play an essential role in the detoxification of pollutants. The potential of using extracellular fungal enzymes for detoxifying organic substances is promising, as it offers an environmentally friendly remediation approach. These enzymes effectively break down and degrade organic pollutants, making them a valuable tool for restoring contaminated environments in a sustainable and eco-friendly manner. The substances comprised coal, agrochemicals, paper leather tanning effects, persistent organic pollutants, pharmaceuticals and personal care products (PPCPs), polycyclic aromatic hydrocarbons (PAHs), and textile dyes. Fungal microbes give an extensive range of enzymes specified in hazardous detoxifying compounds and could be potential candidates for bioremediation of environmental toxic waste. This chapter examines fungal enzymes used in bioremediation, emphasizing their applicability, effectiveness, and role in breaking down environmental waste. It shows how these enzymes are crucial in the remediation process, aiding the removal of pollutants and restoring polluted environments.
... But some scholars believe that thin layer dredging could temporarily reduce total sediment metal concentrations but not heavy metal bioavailability. Heavy metals do not degrade during dredging but transform between soluble and insoluble forms (Peng et al. 2009;Akcil et al. 2015). Continuous extraction, vitrification, and thermal and biological treatments are often used for the assessment and treatment of heavy metals in sediments (Mulligan et al. 2001;Meers et al. 2005;Kim et al. 2011). ...
As a common geo-engineering method to control internal load of nutrients and pollutants, sediment dredging has been used in many freshwater basins and has achieved certain effects. However, dredging can disturb water bodies and substrates and cause secondary pollution. It negatively affects the water environment system mainly from the following aspects. Dredging suddenly changes the hydrological conditions and many physical indicators of the water body, which will cause variations in water physicochemical properties. For example, changes in pH, dissolved oxygen, redox potential, transparency, and temperature can lead to a series of aquatic biological responses. On the other hand, sediment resuspension and deep-layer sediment exposure can affect the cycling of nutrients (e.g., nitrogen, phosphorus), the release and valence conversion of heavy metals, and the desorption and degradation of organic pollutants in the overlying water. This can further affect the community structure of aquatic organisms. The aim of this paper is to analyze the relevant literature on freshwater sediment dredging, and to summarize the current knowledge of the potential environmental risks caused by the dredging and utilization of freshwater sediments. Based on this, the paper attempts to propose suggestions to mitigate these adverse environmental impacts. These are significant contributions to the development of environmentally friendly freshwater sediment dredging technologies.
... Sediment dredging is a popular treatment technique for black odorous water bodies in the last few years, which generates a large amount of contaminated dredged sediment in the treatment process (Cao et al. 2020;Akcil et al. 2015). This sort of sediment is mainly composed of fine-grained silty clay, which is not easy to be consolidated and dried up (Wu et al. 2021). ...
... Despite the gradual improvement of local environmental conditions (Coelho et al., 2014;Oliveira et al., 2018Oliveira et al., , 2022, the effects of the environmental contamination gradient are still significant. While there are several remediation techniques for contaminated ecosystems, such as dredging or capping contaminated sediments with inert materials (Akcil et al., 2015;Pedersen et al., 2015;Peng et al., 2018;Wang et al., 2018;Zia-ur-Rehman et al., 2019), no active remediation actions were taken, and the ecosystem was let to restore itself naturally through natural attenuation. The progressive deposition of less contaminated sediments from upstream should lead to the silting of contaminated layers over time (Ridal et al., 2010) and the reduction of contaminant bioavailability. ...
Mercury’s extreme toxicity and persistence in the environment justifies a thorough evaluation of its dynamics in ecosystems. Aveiro Lagoon (Portugal) was for decades subject to mercury effluent discharges. A Nature-based Solution (NbS) involving Zostera noltei re-colonization is being tested as an active ecosystem restoration mea- sure. To study the effect of Zostera noltei on the sediment contaminant biogeochemistry, seasonal (summer/ winter) sediment, interstitial water and labile mercury vertical profiles were made in vegetated (Transplanted and Natural seagrass meadows) and non-vegetated sites (Bare-bottom area). While no significant differences (p > 0.05) were observed in the sedimentary phase, Zostera noltei presence reduced the reactive/labile mercury concentrations in the top sediment layers by up to 40% when compared to non-vegetated sediment, regardless of season. No differences were found between vegetated meadows, highlighting the fast recovery of the contami- nant regulation ecosystem function provided by the plants after re-colonization and its potential for the reha- bilitation of historically contaminated ecosystems.
... Most in-situ remediation methods are appropriate selections for slightly contaminated sediment (Smolders et al., 2003), and could offer more costeffective (Song et al., 2017;Xu et al., 2022;Zhang et al., 2021) and sustainable solutions (NAVFAC, 2015). To date, some in-situ remedial actions such as capping and monitored natural recovery have been commonly practiced (Jersak et al., 2018), and based on their function, they can be divided into physical, chemical, biological, or hybrid remediation techniques (Song et al., 2017); such as monitored natural recovery (MNR), enhanced monitored natural recovery (EMNR) (Jersak et al., 2016), active and passive capping (Cornelissen et al., 2011;Zhang et al., 2016), Nano-remediation (Xue et al., 2022), stabilization (Akcil et al., 2015;Liu et al., 2019), phytoremediation (Haghnazar et al., 2021), Phyto-microorganisms (Wood et al., 2016), Electrokinetic-acidification, and chemical leaching-ultrasonic (Zhang et al., 2019). In in-situ remediation methods, amendments usually are involved in the process to accelerate the remediation or stabilization process of contaminants (The Interstate Technology & Regulatory Council, 2014). ...
Musa Bay, the largest wetland in Iran and one of the most important Hg-polluted media, plays a significant role in the ecosystem of the area and supports many forms of life. Mercury pollution has detrimental effects on the human body and at high levels leads to the loss of microorganisms in marine ecosystems. Hence, a comprehensive assessment for selecting an effective and sustainable remediation method is crucial to restoring the ecosystem promptly. The determination of a proper and practical treatment method not only is a case-based approach, but could be challenging due to its multi-criteria decision-making nature. Considering preferred crucial factors involved in the effectiveness of remedial actions, in this study a questionnaire is designed to assess the opinion of environmental experts, stakeholders, and some occupants of the area on remedial actions based on the importance weights of criteria. Subsequently, practical remediation and management strategies ranked by hybrid FVIKOR as a multi-criteria decision making (MCDM) method. Ranking results show that dredging and stabilization could offer a promising solution for the remediation of the case study. The results of the study demonstrate that the development of MCDM methods along with effective criteria and considering the analysis of the questionnaires, could offer the best remediation strategy for a specific contaminated site.
In this study, Rhodamine B dye (RhB) is effectively removed from aqueous solutions by using nano‐MgO and nano‐MgO activated carbon as an adsorbent. First, potassium hydroxide was used in a chemical activation process to create activated carbon from the Anacardium occidentale shell, often known as the cashew nutshell. Rosa cymose extract was used in a quick precipitation process to create nano‐magnesium oxide in a sustainable way. Activated carbon composite impregnated with nano‐magnesium oxide was made using a dropwise process. The study examined the nanocomposite that removed the dye Rhodamine B from the aqueous solution. Using SEM, XRD, FTIR, and EDX, the nano‐Mgo and nano‐MgO‐AC were analyzed. Using a scanning electron microscope, an analysis was conducted on the evenly distributed accumulation of MgO nanoparticles added to the activated carbon. The capability of nano‐MgO‐activated carbon to decolorize RhB was investigated. The effects of beginning pH ranges of 2.0–9.0, initial dye concentrations of 10–40 ppm, biosorbent dosages of 0.2–1.2 g, and contact times ranging from 10 to 60 min were investigated. At pH 5, most dye was eliminated. The work has shown that RhB may be effectively removed from aqueous medium using nano‐MgO‐AC, it could potentially be used as an affordable adsorbent material. Equilibrium estimations were acknowledged strongly through Langmuir approximations with a correlation determination of 0.985.
The quest for sustainable mining processes has directed research towards environmentally friendly alternatives to conventional beneficiation practices, with biosurfactants emerging as a viable option due to their lower environmental impact. This study reviews the application of biosurfactants as bioreagents in mineral flotation, exploring their production, their mechanisms of action, and the sustainability benefits they offer. Methods include a decade-long text mining analysis of relevant literature, utilizing software tools like Zotero on platforms like Web of Science to extract and analyze data. The results underscore the growing interest in biosurfactants over the last ten years, highlighting their increasing relevance in industrial applications such as mineral flotation, where they replace synthetic surfactants. Particularly, biosurfactants have shown effectiveness in enhancing the froth flotation process, leading to more efficient mineral recovery while mitigating environmental harm. In conclusion, the adoption of biosurfactants in mineral processing not only aligns with sustainability goals but also demonstrates potential improvements in operational efficiency, offering a dual benefit of environmental protection and enhanced resource recovery.
In the era of globalization and rising population growth demands rapid urbanization, industrialization, and intense agricultural production causing pollution in water bodies. Mycoremediation is one of the prospects that provides eco-friendly remediation strategies for wastewater. Fungi are highly tolerant to different toxicants, making them one of the potent agents for wastewater treatment. This review deals with the mechanism of fungus-mediated degradation of different pollutants present in wastewater. However, the working principles may vary among different fungal species, and the degree of efficacy may also differ. Light intensity, pH, and temperature are the major controlling factors that play a critical role in mycoremediation. Different value-added products like enzymes, pharmaceutical products, biofuel, Single cell protein (SCP), and many more are also being produced during the degradation of toxic pollutants by fungal biomass. All these synthesized products have their own application in different sectors. This review is a compilation of mycoremediation strategies and products with added value that will serve as a solid foundation for future researchers.
A large amount of sediment is dredged from surface water bodies such as rivers, lakes, and oceans every year around the world. It should be further disposed of or recycled. Dewatering is an essential step before the treatment and recycling of dredged sediment. At present, flocculation is one of the most used techniques for dewatering of dredged sediment. This article provides a comprehensive review on the status of dewatering of dredged sediment in water bodies by flocculation processes, with emphasis on the self-flocculation process of dredged sediment and the effects of adding different flocculants. The important influencing factors for the self-flocculation process of dredged sediment were summarized, and the corresponding mechanisms were discussed. The mainly used flocculants for the flocculation process and their influencing mechanisms for the properties of the flocs were also reviewed. In addition, the effect of the flocculants on the migration of contaminants in dredged sediment was assessed. This review can provide reference and guidance for future studies and the real projects on dewatering of dredged sediment by flocculation processes.
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Mercury (Hg) contamination is acknowledged as a global issue and has generated concerns globally due to its toxicity and persistence. Tunable surface-active sites (SASs) are one of the key features of efficient BCs for Hg remediation, and detailed documentation of their interactions with metal ions in soil medium is essential to support the applications of functionalized BC for Hg remediation. Although a specific active site exhibits identical behavior during the adsorption process, a systematic documentation of their syntheses and interactions with various metal ions in soil medium is crucial to promote the applications of functionalized biochars in Hg remediation. Hence, we summarized the BC's impact on Hg mobility in soils and discussed the potential mechanisms and role of various SASs of BC for Hg remediation, including oxygen-, nitrogen-, sulfur-, and X (chlorine, bromine, iodine)-functional groups (FGs), surface area, pores and pH. The review also categorized synthesis routes to introduce oxygen, nitrogen, and sulfur to BC surfaces to enhance their Hg adsorptive properties. Last but not the least, the direct mechanisms (e.g., Hg-BC binding) and indirect mechanisms (i.e., BC has a significant impact on the cycling of sulfur and thus the Hg-soil binding) that can be used to explain the adverse effects of BC on plants and microorganisms, as well as other related consequences and risk reduction strategies were highlighted. The future perspective will focus on functional BC for multiple heavy metal remediation and other potential applications; hence, future work should focus on designing intelligent/artificial BC for multiple purposes.
Heavy metal (HM) exposure is regarded as one of the greatest environmental concerns worldwide due to their non-biodegradability, high bioaccumulation in the food chain, and most importantly, human carcinogenicity. The industrial uses of chromium (Cr) are diverse and include metallurgy, paint, leather tanning, and electroplating. Because of inadequate waste discharge regulations, toxic amounts of Cr are released into the environment, severely damaging the ecosystem. It is now understood that Cr has some advantages for humans in its trivalent oxidation form [Cr(III)] as a micronutrient. However, its hexavalent form [Cr(VI)] is a strong carcinogen and has no recognized biological functions. Over the years, a number of physico-chemical, and biobased techniques have appeared in the effort to eliminate Cr from the environment. Bioremediation of Cr have several advantages over the conventional physical and chemical treatment methods due to its low cost, environment friendly practices and sustainability. Bacteria employs several mechanisms such as biosorption, efflux, bioreduction and bioaccumulation that they possess either inherently or have acquired to counter the toxic effects of Cr with time. This chapter focuses in detail on microbial mechanisms and responses against Cr toxicity, their applications and challenges in real time applicability of these. Further, the latest strategies and solutions in developing bioremediation applications are also discussed in this chapter. Nanobioremediation, immobilization techniques and use of enhancers have immense scope in improving the bioremediation efficiency and also in metal recovery. This information will be helpful in understanding the current status of research of Cr pollution remediation and bridging the gap between lab scale findings and its real time applicability in the environment.
In this study, we investigated the heavy metal absorption of Alcaligenes faecalis strain U.B.I., a bacteria isolated from a mining site, under different environmental conditions. We utilized both conventional and molecular techniques to identify the bacteria and employed response surface methodology (R.S.M.) to determine optimal environmental conditions for heavy metal absorption. Our analysis revealed that the heavy metal-tolerant bacteria belong to the Proteobacteria, specifically the Betaproteobacteria order in the Burkholderiales family. Additionally, the bacteria’s phylogenetic characteristics indicated a close relationship between the Aeromonas sp. cluster and members of the Aeromonadaceae family. Our results showed that the biomass A. faecalis strain U.B.I. had an optimal potential for chromium (Cr+) absorption at 93.0%. We also conducted tests on the biomass under optimized conditions for lead (Pb2+) absorption using R.S.M., resulting in a mean heavy metal uptake of 89.99%. Furthermore, we analyzed the surface functional groups after interaction with heavy metals and observed a significant shift in position of the functional groups. The O-H stretch and H-bonded at the 3268 cm1 position, while C=C stretch and N-O asymmetrical stretch/C-O stretch occurred at positions 2195 cm-1 and 1629 cm-1 of the spectra, respectively. Our findings suggest that the biomass of A. faecalis strain U.B.I. has potential for heavy metal bioremediation and can be used for heavy metal biosorption under various environmental conditions.
To date, the field of microalgae has been slowly evolving and expanding to accommodate various industries from food and feed to biofuel production coupled with wastewater treatment which subsequently allowed greater access of water for daily usage. This technology is gradually proving its value, despite its limited use in the market. With the depletion of freshwater resources, conventional treatment methods are being replaced by microalgae-mediated wastewater treatment. This method not only has a lower environmental footprint and produces less chemical waste, but also captures nutrients more efficiently than conventional methods which would be subsequently consumed for the development of microalgal biomass. Several factors that influence the recovery of nutrients such as phosphorus and nitrogen that are crucial for algal growth are discussed accordingly in this chapter, including wastewater characteristics, turbidity, concentration of phosphorus and nitrogen as well a chemical oxygen demand and biological oxygen demand. Additionally, currently available microalgae-based wastewater technologies are introduced along with the respective advantages and disadvantages. Sustainability prospect of microalgae-based wastewater technologies is also examined. Lastly, this chapter also includes the potential challenges that hinder the development and commercialization of microalgae-based wastewater technologies and provides adequate future recommendations for resolving the current concerns.
Textile industry that has less optimal waste management due to the absence of a wastewater treatment plant (WWTP) tends to dispose the waste directly into the water or river. Most farmers near industrial area use liquid waste for irrigation water. This generates negative impacts of complicated problems in the agricultural sector, especially heavy metals contamination in paddy soils. In such case, bioremediation can be done to handle the contaminated soils by heavy metals to create a healthy farming environment. The purpose of this study was to determine the effectiveness of the chelating agents ( Agrobacterium sp. I37 or compost) to the characteristic of soil and the level of Pb in rice plant. This study was conducted between June - September 2017 in Tasikmadu, Karanganyar, Indonesia. The experimental design was factorial using randomized completely block design (RCBD) as the based design. There are two factors in this research: a) inorganic fertilizer (P): without inorganic fertilizer (P0) with inorganic fertilizer (P1); b) chelator (B): without chelator (B0), with chelator Agrobacterium sp I37 (B1), with chelator compost (B2). There were six treatment combinations then replicated 3 times for each treatment, so there were 18 unit treatments. The results showed that Agrobacterium sp. I37 or compost can decrease soil Pb. The best treatment in decreasing soil Pb was treatment using Agrobacterium sp. I37, which soil Pb decreased of 42.91% from 8.04 mg/kgto 4.59 mg/kg; could enhance accumulation of Pb in the roots of 69, 63% and decrease Pb levels in rice grains around 55.67% higher than control treatment.
Hydrogels have been widely used for adsorbing heavy metal ions in wastewater treatment. Herein, a calcium alginate/poly‐N‐isopropylacrylamide double‐network hydrogel with photothermal responsiveness was prepared for adsorbing heavy metal ions in aqueous solution. The chemical composition, micromorphology, swelling properties, photothermal responsiveness, adsorption properties, and adsorption mechanism of gel microspheres were studied, respectively. The gel microspheres had an interpenetrating three‐dimensional porous structure, and their high porosity morphology and high specific surface area could ensure the adequate exposure of active adsorption sites. The gel microspheres showed excellent selective adsorption of Cr(III), and the theoretical maximum adsorption capacity of 146.16 mg/g was calculated according to the Langmuir model. Besides, its excellent photothermal conversion ability enhanced the resistance to external interference after the adsorption. Our work has provided an innovative approach to solar water purification while optimizing the preparation process.
Preliminary experimental results on the solification/stabilzation of dredged marine sediments (MS) and the non-metallic fraction of automotive shredder residues (NMASR) with coal fly ashes (CFA) are reported. Lab scale experiments of wet granulation at room temperature of these wastes are presented and discussed: cement was used as a binder, while water addition was dosed to optimize granules amount and size.
The obtained granules were then subjected to standard leaching tests according to Italian regulation. The results of the leaching tests showed, for all the experimented wastes, a good level of stabilization: heavy metals and ions content was within the limits provided by Italian regulation for landfill disposal as not dangerous waste, while a COD content exceeding the above mentioned limit was detected. This was attributed to plastics and an organic contamination by vehicles fluids in the case of NMASR, and to sulphides and iron content in the case of marine sediments.
Heavy metals are stable and persistence environmental contaminant of marine sediments. The vast increase in population growth, urbanisation and industrialisation leads to increase in of marine discharges, which results in total loads of pollutants being delivered to the sea. Heavy metal pollution in aquatic environment and subsequent uptake in food chain by aquatic organisms and humans put public health at risks. However, even at lower concentrations heavy metals like Cd, Hg, Cr and Pb may exhibit extreme toxicity under certain condition. Thus, this makes regular monitoring of aquatic environment to be more imperative and necessary. This paper therefore, review the occurrence of heavy metals and various speciation methods used for heavy speciation in soil and sediments.
This review presents developments and applications in bioleaching and mineral biooxidation since publication of a previous mini review in 2003 (Olson et al. Appl Microbiol Biotechnol 63:249-257, 2003). There have been discoveries of newly identified acidophilic microorganisms that have unique characteristics for effective bioleaching of sulfidic ores and concentrates. Progress has been made in understanding and developing bioleaching of copper from primary copper sulfide minerals, chalcopyrite, covellite, and enargite. These developments point to low oxidation-reduction potential in concert with thermophilic bacteria and archaea as a potential key to the leaching of these minerals. On the commercial front, heap bioleaching of nickel has been commissioned, and the mineral biooxidation pretreatment of sulfidic-refractory gold concentrates is increasingly used on a global scale to enhance precious metal recovery. New and larger stirred-tank reactors have been constructed since the 2003 review article. One biooxidation-heap process for pretreatment of sulfidic-refractory gold ores was also commercialized. A novel reductive approach to bioleaching nickel laterite minerals has been proposed.
Nonlinear dynamic rolling forces in the vertical and horizontal directions are, respectively, established, considering the impact of vertical and horizontal directions vibration of rolls. Then a vertical-horizontal coupling nonlinear vibration dynamic model of rolling mill rolls is proposed, based on the interactions between this dynamic rolling force and mill structure. The amplitude-frequency equations of the main resonance and inner resonance are carried out by using multiple-scale method. The characteristics of amplitude frequency under nonlinear stiffness, damping, and amplitude of the disturbance are obtained by adopting the actual parameters of 1780 rolling mills. Finally, the bifurcation behavior of the system is studied, and it is found that many dynamic behaviors such as period, period-3 motion, and chaos exist in rolling mill, and this behavior could be restrained effectively by choosing proper system parameters.
Biosorption is a physico-chemical and metabolically-independent process based on a variety of mechanisms including absorption, adsorption, ion exchange, surface complexation and precipitation. Biosorption processes are highly important in the environment and conventional biotreatment processes. As a branch of biotechnology, biosorption has been aimed at the removal or recovery of organic and inorganic substances from solution by biological material which can include living or dead microorganisms and their components, seaweeds, plant materials, industrial and agricultural wastes and natural residues. For decades biosorption has been heralded as a promising cost-effective clean-up biotechnology. Despite significant progress in our understanding of this complex phenomenon and a dramatic increase in publications in this research area, commercialization of biosorption technologies has been limited so far. This article summarizes existing knowledge on various aspects of the fundamentals and applications of biosorption and critically reviews the obstacles to commercial success and future perspectives.
The ability of heavy metals bioaccumulation to cause toxicity in biological systems—human, animals, microorganisms and plants—is an important issue for environmental health and safety. Recent biotechnological approaches for bioremediation include biomineralization (mineral synthesis by living organisms or biomaterials), biosorption (dead microbial and renewable agricultural biomass), phytostabilization (immobilization in plant roots), hyperaccumulation (exceptional metal concentration in plant shoots), dendroremediation (growing trees in polluted soils), biostimulation (stimulating living microbial population), rhizoremediation (plant and microbe), mycoremediation (stimulating living fungi/mycelial ultrafiltration), cyanoremediation (stimulating algal mass for remediation) and genoremediation (stimulating gene for remediation process). The adequate restoration of the environment requires cooperation, integration and assimilation of such biotechnological advances along with traditional and ethical wisdom to unravel the mystery of nature in the emerging field of bioremediation. This review highlights better understanding of the problems associated with the toxicity of heavy metals to the contaminated ecosystems and their viable, sustainable and eco-friendly bioremediation technologies, especially the mechanisms of phytoremediation of heavy metals along with some case studies in India and abroad. However, the challenges (biosafety assessment and genetic pollution) involved in adopting the new initiatives for cleaning-up the heavy metals-contaminated ecosystems from both ecological and greener point of view must not be ignored.
The efficiency and mechanism of nano-hydroxyapatite (nHA) in immobilizing Pb and Cd in contaminated soil were assessed in this work. The X-ray diffraction analysis indicated that the key mechanisms for Pb/Cd immobilization in the soil involve both surface complexation on the surface of nHA and dissolution of the nHA amendments and precipitation of Pb/Cd-containing phosphates. We tested the effects of different nHA dose (the molar ratio of P/(Pb+Cd)) on the water extraction of heavy metals, and phytoavailability of soil metals. The nHA application could significantly reduce water soluble Pb with 72% and Cd with 90%, bioaccessible Pb with a reduction of 12.5-27.5% and Cd with a reduction of 17.66-34.64%, respectively. The nHA reduced phytoavailability of Pb and Cd with 65.3% and 64.6% in contaminated soil, respectively. In addition, the treatment efficiency increased along with the nHA dose (based on the molar ratio of P/(Pb+Cd)) increased, and most effective ratio was molar ratio of P/(Pb+Cd) at 5:1. The results in this study showed that nHA can immobililize Pb and Cd in contaminated soil effectively.
Bioleaching of metal sulfides is performed by a diverse group of microorganisms. The dissolution chemistry of metal sulfides follows two pathways, which are determined by the mineralogy and the acid solubility of the metal sulfides: the thiosulfate and the polysulfide pathways. Bacterial cells can effect this metal sulfide dissolution via iron(II) ion and sulfur compound oxidation. Thereby, iron(III) ions and protons, the metal sulfide-attacking agents, are available. Cells can be active either in planktonic state or in forming biofilms on the mineral surface; however, the latter is much more efficient in terms of bioleaching kinetics. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows an electrostatic attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions is the mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in non-contact leaching. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a redox chain forming a supercomplex spanning the periplasmic space and connecting both outer and inner membranes. In this review, we summarize some recent discoveries relevant to leaching bacteria which contribute to a better understanding of these fascinating microorganisms. These include surface science, biochemistry of iron and sulfur metabolism, anaerobic metabolism, and biofilm formation. The study of microbial interactions among multispecies leaching consortia, including cell-to-cell communication mechanisms, must be considered in order to reveal more insights into the biology of bioleaching microorganisms and their potential biotechnological use.
Bottom sediments in coastal regions have been considered the ultimate sink for a number of contaminants, e.g., toxic metals. In this current study, speciation of metals in contaminated sediments of Oskarshamn harbor in the southeast of Sweden was performed in order to evaluate metal contents and their potential mobility and bioavailability. Sediment speciation was carried out by the sequential extraction BCR procedure for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn and the exchangeable (F1), reducible (F2), oxidizable (F3), and residual (R) fractions were determined. The results have shown that Zn and Cd were highly associated with the exchangeable fraction (F1) with 42-58 % and 43-46 %, respectively, of their total concentrations in the mobile phase. The assessment of sediment contamination on the basis of quality guidelines established by the Swedish Environmental Protection Agency (SEPA) and the Italian Ministry of Environment (Venice protocol for dredged sediments) has shown that sediments from Oskarshamn harbor are highly contaminated with toxic metals, especially Cu, Cd, Pb, Hg, As, and Zn posing potential ecological risks. Therefore, it is of crucial importance the implementation of adequate strategies to tackle contaminated sediments in coastal regions all over the world.
An account is presented of a series of investigations and collaborative studies, initiated by BCR, on current methods of metal speciation by extraction of soils and sediments with chemical reagents. It was established by extensive consultation with European experts that the diverse procedures used could be harmonized into agreed methods. These methods, including both single extractant and sequential extraction procedures were subjected to collaborative, interlaboratory trials and the results, presented briefly here, showed that it was both possible and desirable that reference soils and sediments, characterised by certified values for extractable contents, be prepared. As a consequence of these studies two soils have been prepared and will shortly be the subject of interlaboratory analysis with a view to certification of their EDTA and acetic acid extractable contents of some heavy metals. Following this workshop a feasibility study of the agreed sequential extraction procedure will, it is believed, shortly lead to certification of sediments for contents extractable by a defined sequential extraction procedure.
Most sediment dredged in Italian harbours is discharged into coastal areas. Italian legislation provides physical and chemical characterisations of dredged material. However, to determine whether materials are discharged to a dumping site, used for coastal nourishment or other beneficial use, toxicological assessment should be required. In 1995, 12 sediment cores were taken from dredged areas of Viareggio harbour (Tyrrhenian coast). Nine superficial sediments were collected in two coastal areas: a disposal site and a potential nourishment site. Particle size, total organic matter, heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls were analysed. In order to assess sediment toxicity and evaluate the best destination, three bioassays were performed on two harbour and one offshore superficial samples using Vibrio fisheri, Corophium volutator and larvae of Crassostrea gigas.
The different harbour areas showed an increase of contaminant levels from the entrance to the inner zones. A comparison of sediment quality of the harbour and coastal areas (physical, chemical and ecotoxicological characteristics) suggested that materials dredged from different areas should be handled in different ways depending on contaminant types and loads. Dredged sediments could be dumped off-shore without decontamination or further use, used to build up eroded areas or be subjected to on-site decontamination treatment.
This study deals with laboratory-scale investigations to evaluate the efficiency of different chemical leaching agents (i.e. sulfuric, oxalic and citric acids) and bioleaching processes (based on different acidophilic bacterial strains) on the mobilisation of metals/semi-metals in contaminated harbour sediments. A simplified life-cycle assessment was also performed in order to compare the investigated strategies in terms of their main environmental impacts. The different chemical leaching agents provided different extraction efficiencies of toxic metals. Among the investigated chemical leaching agents, citric acid 0.5 M and sulfuric acid pH 2 were the most effective, with average mobilisation efficiencies of 30% for Zn and Cr, 40% for Ni, and 35 and 58% for As, under citric and sulfuric acid, respectively. Similar higher extraction efficiencies of metals were also observed in bioleaching experiments with the presence of ferrous iron. The life-cycle assessment revealed that treatments based on diluted sulfuric acid are a better option considering both resource requirements and emissions, leading to lower environmental impacts compared with the other treatment strategies. Overall results from this study provide new insights for the definition of the most efficient and environmentally friendly strategies to be used for dredged sediments contaminated with metals.
Filamentous fungi and lithotrophic bacteria were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. A preliminary physico-chemical characterization of the sediments comprising a sequential extraction study revealed their high metallic contamination and a predominant association of the metals with sulphides and organic matter. The mobility of heavy metals from sediments was ranked by decreasing order as follows: Mn > Zn > Cd > Cu > Pb. The conditions that favoured the solubilization of heavy metals by filamentous fungi turned out to be also favourable for the activity of the sediment organotrophic bacteria. The latter produced organic acids under temporary hypoxic conditions and resulted in the solubilization of 77% of manganese, 44% of zinc, 12% of copper, and less than 2% of cadmium or lead. In general, the fungal organotrophic treatments were limited to the relatively mobile metals due to the weak nature of the organic acids produced and to their microbial consumption under limited saccharose conditions. The lithotrophic treatments yielded higher solubilization results than the organotrophic experiments. Sulphur resulted in a faster, and for some metals such as copper and cadmium, in better bioleaching results compared with reduced iron or with a combination of reduced iron and sulphur. The bioleaching percentages varied between 72 and 93% for cadmium, copper, manganese and zinc, except for lead because of the poor solubility of lead sulphate. The sediment's lithotrophic bacteria acidified the matrix through sulphur oxidation, and leached both loosely and tightly bound metals.
The present study was aimed at assessing the per-formance of different nonliving macrophytes sampled in the Adriatic coast in arsenic(V) sorption. Full factorial experiments were carried out where the main factors were the macrophyte species (brown algae: Cystoseira, Dictyopteris, and Eisenia; green algae: Caulerpa and Ulva; red algae: Ceramium, Gracilaria, and Porphyra; and seagrass: Zostera), biosorbent washing pre-treatment (deionized water, acid pH 2 and basic pH 10), equilibrium pH (in the range 1 to 8), under relatively high (10 mg L −1) and relatively low (100 μg L −1) arsenic concentration. All species exhibited significant adsorption. Indeed, they showed a good performance, with the highest observed value of about 1.3±0.1 mg g −1 for the red alga Ceramium and the seagrass Zostera, comparable with those of activated carbon and other low-cost adsorbents reported in the literature under similar experimental conditions. Moreover, red algae known in the literature to be bad cationic metal sorbents showed very good arsenic sorption performance. This work shows that the performance of arsenic biosorption depends on many factors: the different composition and struc-ture of outer layer of the macrophytes, arsenic speciation and functional group availability under different pH, and eventual counter-ion interactions with arseniate.
The removal of heavy metals from contaminated river sediments was studied using suspension leaching under laboratory conditions and percolation leaching in a pilot plant. The leaching potential of indigenous sulfur-oxidizing bacteria was compared with acid treatment. Bioleaching with elemental sulfur as substrate was found to be better than treatment with sulfuric acid for the solubilization of all metals tested. The physical and chemical properties of the sediments used in this study did not affect leaching capacity under optimum conditions in the laboratory.
Under the practical conditions in the pilot plant, the redox state of sludge had a considerable influence on leaching efficiency. In a deposited oxic sediment with good permeability, about 62% of the metals tested were removed by percolation leaching after 120 days. Zn, Cd, Ni, Co and Mn were sufficiently leached to enable treated sediments to be reused as soil. In a freshly dredged anoxic sediment, only a total of 9 % of metals were removed. The results indicate that freshly dredged sediments need to undergo pretreatment before percolation leaching to improve mass transfer and to activate the leaching active bacteria.
The effects of sulfur concentration on the bioleaching of heavy metals from the sediment by indigenous sulfuroxidizing bacteria were investigated in an air-lift reactor. Increasing the sulfur concentration from 0.5 to 5 g/l enhanced the rates of pH reduction, sulfate production and metal solubilization. A Michaelis-Menten type equation was used to explain the relationships between sulfur concentration, sulfate production and metal solubilization in the bioleaching process. After 8 days of bioleaching, 97-99% of Cu, 96-98% of Zn, 62-68% of Mn, 73-87% of Ni and 31-50% of Pb were solubilized from the sediment, respectively. The efficiency of metal solubilization was found to be related to the speciation of metal in the sediment. From economical consideration, the recommended sulfur dosage for the bioleaching of metals from the sediment is 3 g/l.
Management of contaminated sediments, i.e. linking risk assessment and problem solutions, needs both quality criteria respecting recent findings on the bioavailability of pollutants and in-depth knowledge on processes controlling their particular hydrological and biogeochemical dynamics.
To understand bioavailability is the key issue for managing contaminated sediments. Therefore, scrutiny of the geochemical situation, toxicity, and biodegradability is needed. The first part of this review refers to the new insights into ‘diagenetic’ mechanisms on particles including ageing and their effects on biological interactions.
Chemical and physical methods are described to quantify the retarded desorption behaviour of hydrophobic organic substances and toxic metals. Results of analyses on the extractability of particle-bound pollutants (e.g. solid phase micro-extraction) can be correlated with the bioavailability. Some techniques recently developed to mimic bioavailabilty are briefly summarised. As can be derived from this review, there is a clear need to refine bioavailability models including equilibrium partitioning.
A set of bioassays is a powerful supplement to assess sediment quality. Consequently, a paradigm shift should be initiated for the evaluation of biological data. All information of a survey have to be implemented in an assessment scheme. Multivariate statistics and fuzzy mathematics provide promising means to interpret multiple data pattern.
The leaching characteristics of zinc and lead in two contaminated sediments were studied, and the effect of low molecular weight organic acids (LMWOAs) and pH value on the leaching of zinc and lead from two contaminated sediments were examined. The results showed that zinc and lead in the sediments were partly dissolved by three LMWOA solutions under different concentrations in batch experiment. The leaching of heavy metals from two sediments followed the descending order: citric acid > malic acid > tartrate acid (for zinc); citric acid > tartrate acid > malic acid (for lead). The leaching concentrations of heavy metals in solution were enhanced with the increasing of LMWOA concentration and the decreasing of pH value. In addition, all LMWOAs leached more heavy metals than inorganic salt did. The leaching capability under the condition of LMWOAs followed the order: zinc > lead.
Three laboratory experiments investigating the feasibility of extracting lead from saturated Norwegian marine clay by electrokinetic remediation is presented. Cylindrical specimens of 10 cm in diameter and 5 cm in length were treated under constant direct current with electrodes placed at each side of the specimens in a liquid. Electrokinetic remediation enhancement techniques were also investigated by using acetic acid depolarization of the cathode reaction and an ion-selective membrane that veils hydroxyl ion back-transport at the cathode. The results were compared with electrokinetic remediation without enhancement after 52 days of treatment.
This article outlines the important biogeochemical roles that fungi play in the degradation, utilization, and transformation of organic and inorganic substrates. Fungal populations are intimately involved in biogeochemical transformations at local and global scales and such processes have major implications for other aspects of living organisms, notably plant productivity and human health. While most prior attention has focused on carbon and nitrogen cycling, the involvement of fungi in almost all other elemental cycles is emphasized. Of special significance are the mutualistic relationships with phototrophic organisms, lichens (algae, cyanobacteria) and mycorrhizas (plants). Some of these fungal transformations have beneficial applications in environmental biotechnology, for example, in metal leaching, recovery and detoxification, and xenobiotic and organic pollutant degradation. Adverse effects may also result when these processes are associated with the degradation of foodstuff, natural products, and building materials.
Most sediment dredged in Italian harbours is discharged into coastal areas. Italian legislation provides physical and chemical characterisations of dredged material. However, to determine whether materials are discharged to a dumping site, used for coastal nourishment or other beneficial use, toxicological assessment should be required. In 1995, 12 sediment cores were taken from dredged areas of Viareggio harbour (Tyrrhenian coast). Nine superficial sediments were collected in two coastal areas: a disposal site and a potential nourishment site. Particle size, total organic matter, heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls were analysed. In order to assess sediment toxicity and evaluate the best destination, three bioassays were performed on two harbour and one offshore superficial samples using Vibrio fisheri, Corophium volutator and larvae of Crassostrea gigas.
The search for cheap and environmentally friendly materials is essential for remediation of heavy-metal-contaminated agricultural soils. A pot experiment was undertaken to evaluate the application of rice straw and filamentous fungus Penicillium chrysogenum (P. chrysogenum) on the fractionation of copper (Cu) and cadmium (Cd), soil microbial properties, and Cu and Cd uptake by romaine lettuce (Lactuca sativa) in a contaminated agricultural soil. Rice straw was applied at three rates (0, 7.8, and 11.7 g kg−1 soil), and in combinations with P. chrysogenum (1.0 × 106 spores g−1 soil). It was found that the combined treatment of rice straw and P. chrysogenum significantly decreased the acid-extractable Cu and Cd by 15.4–25.1% and 20.2–27.3%, and increased the oxidizable Cu and Cd by 16.1–18.0% and 72.1–98.4%, respectively. Soil microbial biomass and fresh weight of lettuce were also remarkably enhanced after rice straw plus P. chrysogenum addition. Rice straw combined with P. chrysogenum was more effective in reducing Cu and Cd uptake by lettuce than rice straw alone. The joint application of rice straw and P. chrysogenum remarkably reduced Cu and Cd concentrations in lettuce shoots by 13.6–21.9% and 32.9–41.7%, respectively. These results indicate that the combined application of P. chrysogenum and rice straw is a promising method to alleviate the bioavailability of metals, and to improve soil microbial properties and plant yield in heavy-metal-polluted agricultural soils.
Economic and environmental assessments of products are commonly performed at product level in a comparative way to identify possible improvement solutions. The problem with this approach is that introduction of new technologies leads to increased functionality that alters the economic and environmental impacts. In addition, a growing market leads to the demand for higher volume of products. When these factors are combined, overall increase in economic and environmental impacts occurs in the society even though improvements were made at product level. Therefore, this research article proposes a new approach to product assessment to cater for technology changes and increasing volume. Using Axiomatic Design Theory, the drivers of economic and environmental impacts are identified by characterising these impacts as a function of product features. The assessment method is applied for a range of functionality and increasing volume to determine the total economic and environmental impact caused in society. Furthermore, ratio analysis is used to determine the economic and environmental impact changes over product generations to identify additional environmental improvements needed to reach target score. The methodology is validated using a comparative case study of different battery technologies for a range of functionality and assumed volume increase in the next generation of batteries to be produced.
The aim of the current work is to develop an environmentally friendly process for the removal of heavy metals (Cu, Zn, Ni, Cd, Al, Cr, Pb) from recycling industry electronic waste with a consortium of Sulfobacillus thermosulfidooxidans and Thermoplasma acidophilum. The performances of commercial S0 powder and biogenic S0 sludge as substrates for the bio-removal of heavy metals were compared. Empirical models for the bioleaching process based on a statistical analysis were developed to evaluate the individual and combined effects of critical variables including S0 dosage, particle size, pulp density and bacterial feed formulation (inoculum size and inoculation style) in shaken flasks while specifying the effective variable ranges. Upscale feasibility experiments in a stirred tank reactor demonstrated a maximum metal bio-removal efficiency (92%) at a 1% dosage of biogenic S0 sludge and 2% dosage of commercial S0 powder (82%), given a 15% pulp density and 150 μm particle size with an intermittent low-concentration addition of inoculum (1ｘ106 cells/mL). Biogenic S0 sludge showed a higher degree of S0 oxidation (95%) in a shorter time period (12 days) compared to commercial S0 powder (82% in 24 days), thereby reducing the process cost. Risk assessments of discarded electronic wastes before and after bioremediation by the toxicity characteristic leaching procedure (TCLP), waste extraction test (WET), synthetic precipitation test (SPLP) and total threshold limit concentration (TTLC) indicated that the leaching/toxicity of bio-remediated residue was well within the regulatory limits.
The driving force behind sustainable behaviour in remediation is poorly understood.•We used factor analysis to classify 27 sustainability considerations.•We used structural equation model to analyse determinants of sustainable behaviour.•The effects of stakeholder influence and institutional pressure were quantified.•The study identified key areas for improvement to promote sustainable practices.
Sandy loam soil polluted with heavy metals (As, Cu, Pb and Zn) from an ancient Mediterranean Pb mining and metallurgy site was treated by means of wet high-intensity magnetic separation to remove some of the pollutants therein. The treated fractions were chemically analysed and then subjected to magnetic characterisation, which determined the high-field specific (mass), magnetic susceptibility (κ) and the specific (mass) saturation magnetisation (σS), through isothermal remanent magnetisation (IRM) curves. From the specific values of κ and σS, a new expression to assess the performance of the magnetic separation operation was formulated and verified by comparison with the results obtained by traditional chemical analysis. The magnetic study provided valuable information for the exhaustive explanation of the operation, and the deduced mathematical expression was found to be appropriate to estimate the performance of the separation operation. From these results we determined that magnetic soil washing was effective for the treatment of the contaminated soil, concentrating the majority of the heavy metals and peaking its separation capacity at 60% of the maximum output voltage.
Several methods to evaluate the environmental process impact assessment of industrial chemical processes have been presented in the literature. Although these methods follow the same steps (usually, characterisation, normalisation and weighting), each method addresses different impact categories, considering specific nomenclatures and using different taxonomies to classify their outputs. When industrial chemical processes are being assessed by several methods, different results are obtained. The comparison of these non-standardised results turns out to be a difficult task. This work has two main contributions that help in the choice of the most appropriate method to be used. First, standardise the taxonomy used by the different methods and second, propose a quantitative framework that combines different methods into a final score. Therefore, it is suggested a standard taxonomy, which allows to report the output of the different methods in a systematic way. A new concept called impact categorical groups is also proposed. These groups aggregate similar impact categories presented by different methods, and therefore allow the comparison of the obtained results by different methods. A framework to aggregate impact category indicators from different methods into a final score (index) is also presented. This framework also suggests a path to determine the best method to be applied and provides an insight on the weighting factors that should be considered in the aggregation of the different indicators into the final index. The basis for the proposed achievements was an extensive literature review, which includes 25 methods for environmental process impact assessment.
In this study, the feasibility of a washing process to extract Cd, Cu, Ni, Pb, and Zn from three real dredged marine sediments (Namhang (NH), Bangeojin (BE), and Haengam (HA) bay sediments, South Korea) were investigated using various washing agents (ethylenediaminetetraacetic acid (EDTA), NaCl, HCl, sodium citrate, and HNO3). Even though the removal efficiencies of heavy metals were not high, which is thought to be largely due to the high concentrations of Fe and Ca, EDTA was a more efficient extraction agent for heavy metals compared to the other agents, because EDTA formed more stable complexes with metals. EDTA removed: 30%, 43%, and 9% of Cu; 48%, 66%, and −8% of Pb; and 31%, 60%, and −14% of Zn from NH, BE, and HA sediments, respectively. Additionally, fractionation analysis showed that EDTA converted the strongly bound fractions of Cu and Pb to an exchangeable fraction. Based on the experimental results, the washing technique using EDTA is determined to be efficient for the removal Cu, Pb, and Zn from NH and BE sediment samples. On the contrary, residual concentrations of heavy metals were not decreased from HA samples compared to extraction with washing solution because of the high content of fine particles and organic matter in samples. Furthermore, the fractionations of metals highly influenced the chemical extraction of metals in sediments, and the fractionation changes after chemical washing increased the total extractable amount of metals. As a result, the fractionation change caused changes in the bioavailability and potential mobility of metals.
Hydrophobic organic compounds (HOCs) are modeled as being distributed between aqueous, micellar, and sorbent compartments in a soil/aqueous system containing nonionic surfactant micelles. The partitioning of HOC between the hydrophobic interiors of the nonionic surfactant micelles and the surrounding solution can be characterized with a mole fraction partition coefficient. Nonionic surfactant sorption onto soil may be described by a maximum sorption parameter. Sorbed surfactant molecules tend to increase HOC sorption, and free surfactant monomers in solution tend to decrease HOC sorption by increasing the HOC apparent aqueous solubility; these effects can be represented by a modified HOC soil/water partition coefficient. The distribution of HOC between the three compartments can be estimated using a physicochemical model, for which model parameter values conceptually may be obtained from independent experiments.
Bioleaching strategies are still far from finding real applications in sediment clean-up, although metabolic mechanisms governing bioleaching processes have been deeply studied and can be considered well established. In this study, we carried out bioleaching experiments, using autotrophic and heterotrophic acidophilic bacteria strains, and worked with marine sediments characterized by different geochemical properties and metal concentrations and speciations. The solubilization efficiency of the metals was highly variable, with the highest for Zn (40%-76%) and the lowest for Pb (0%-7%). Our data suggest that the role of autotrophic Fe/S oxidizing bacteria is mainly associated with the production and re-cycling of leaching chemical species, mainly as protons and ferric ions. Metal solubilization appears to be more related to establishing environmental conditions that allow each metal or semimetal to remain stable in the solution phase. Thus, the maintenance of acid and oxidative conditions, the chemical behavior in aqueous environment of each metal species and the geochemical characteristics of sediment interact intimately to influence metal solubilization in site-specific and metal-specific way.
In order to determine whether observed trends in total trace metal content were natural or due to anthropogenic inputs, major and trace elements were measured on three size fractions (fine sand (250-63 μm), silt and clay (<63tμm) and clay (<2μm)) of sediment collected off the Mediterranean coast of Israel. Partitioning of trace metals into carbonate/exchangeable, iron oxide and residual phases for each grain size was also determined. The dominant source of particles was Nile derived material. There was a decrease in Fe/Al, Ti/Al and non-carbonate Mg/Al in the fine sand fraction, interpreted as a decrease in heavy minerals towards the north and an increase in K/Al due to increased feldspars and micas. There was a simultaneous increase in CaCO3 both towards the north and onshore in all grain size fractions due to a northward increase in local biogenic fragments and river detritus. This is consistent with circulation and sediment transport models for the southeast Levantine basin. The background trend in trace metals corresponds to changes in mineralogy. While the fine sand fraction appeared free of contamination, in the finer fractions there is a significant enrichment of Zn, and Cd towards the north, which is not accounted for by changes in mineralogy. The sediments were also enriched in Cu, Zn and Cd near Tel Aviv and Hadera. The peaks near Tel Aviv may correspond to waste discharged through the Yarqon and an old sewage pipe, whilst near Hadera, the Alexander and Hadera Rivers and the terminal for a coal-fired power station may be the source of contamination. There was also clear evidence for contamination by Pb in the finest sediments. However, there was no enrichment in Pb around the point sources of the other trace metals, therefore it was concluded that the majority of Pb contamination was from the atmosphere. All trace metal contamination may be subject to 'smearing' by sediment transport, particularly in the clay fraction.
Bioleaching, also referred to as minerals biooxidation, and bioremediation have been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores, sulfidic-refractory gold concentrates and treatment of acid rock drainage. Technical and commercial challenges, identified in this paper, remain for bioleaching of primary sulfides and complex ores. New frontiers for the technology exist in processing massive sulfides, silicate-locked minerals and in the more distant future in-situ leaching. Decommissioning of cyanide heap leach operations and stabilizing mine wastes using biotechnology are opportunities requiring intensive and focused research, development and engineering efforts.
Hydroxoethylmethacrylate-based macroporous resins are found to be promising new supports for Arthrobacter sp., a metal biosorbing bacterium. The relevant support-biomass complex biosorbs Cu(II) from aqueous solutions and appears to be suitable for partial regeneration.
Biosurfactants are natural products derived from bacteria, yeasts, or fungi. The complex chemical structures and physical properties of biosurfactants generally result in properties equal to, or exceeding, many synthetic surfactants. Biosurfactants have low toxicity profiles to freshwater, marine, and terrestrial ecosystems, and are potential candidates for a variety of environmental applications. Research, to date, has largely been focused on the enhancement of oil biodegradation and microbial enhanced oil recovery. The solubilization and emulsification of toxic pesticides by biosurfactants has also been reported, aiding in the recovery of such hazardous materials from contaminated sites. The future success of biosurfactant technology in bioremediation initiatives will require the precise targeting of the biosurfactant system to the physical conditions and chemical nature of the pollution-affected site.
The solubility of arsenic (As) and heavy metals (Me) from two sediments with differing chemical characteristics and degrees of contamination was quantified by suspension leaching under both aerobic and anoxic conditions. Elemental sulphur (S°) was added as a substrate for the indigenous Thiobacillus spp. The objective of this study was to examine the effects of measures, which attempted to stimulateor to prevent the mobilization of the pollutants in the source material.By stimulating aerobic bioleaching with S°, up to 80% (660 mg/kg) of the As became soluble in a highly polluted lake sediment (Suesser See) in the form of arsenite and arsenate. Without the addition of S°, the As solubility ranged between 0.6 and 3.5 mg/kg. No toxic effects of As (III) on bacterial growth and microbial activity of the indige nous Thiobacillus spp. were observed. By comparison, the As solubility in an oxic sediment from the river Weisse Elster was low (max. 0.5 mg/kg), while the total Me solubility reached 60% (3.7 g/kg).The anaerobic leaching tests were performed under the conditions of a nitrogen atmosphere in a special vessel allowing the redox potential and the pH of the solution to be continuously recorded. In the lake sediment without adding S°, the As solubility increased temporarily; up to 9% of the total As became soluble, and As (III) was the dominant As soluble species (20 mg/kg). In the late leaching phase (—300 mV), the total soluble As decreased, and As (V) became the major soluble species (3.9 mg/kg). In the presence of S°, soluble As and Me were immobilized. The inhibition of As and Me release can be explained by fixation as insoluble sulphides, suggesting that immobilization