Alkali Extraction of Arsenic from Groundwater Treatment Sludge: An Essential Initial Step for Arsenic Recovery.

Arsenic (As)-bearing Fe(III) precipitate groundwater treatment sludge has traditionally been viewed by the water sector as a disposal issue rather than a resource opportunity, partly due to assumptions of the low value of As. However, As has now been classified as a Critical Raw Material (CRM) in many regions, providing new incentives to recover As and other useful components of the sludge, such as phosphate (P) and the reactive hydrous ferric oxide (HFO) sorbent. Here, we investigate alkali extraction to separate As from a variety of field and synthetic As-bearing HFO sludges, which is a critical first step to enable sludge upcycling. We found that As extraction was most effective using NaOH, with the As extraction efficiency increasing up to >99% with increasing NaOH concentrations (0.01, 0.1, and 1 M). Extraction with Na2CO3 and Ca(OH)2 was ineffective (<5%). Extraction time (hour, day, week) played a secondary role in As release but tended to be important at lower NaOH concentrations. Little difference in As extraction efficiency was observed for several key variables, including sludge aging time (50 days) and cosorbed oxyanions (e.g., Si, P). However, the presence of ∼10 mass% calcite decreased As release from field and synthetic sludges considerably (<70% As extracted). Concomitant with As release, alkali extraction promoted crystallization of poorly ordered HFO and decreased particle specific surface area, with structural modifications increasing with NaOH concentration and extraction time. Taken together, these results provide essential information to inform and optimize the design of resource recovery methods for As-bearing treatment sludge.

Comparing cadmium uptake kinetics, xylem translocation, chemical forms, and subcellular distribution of two tobacco (Nicotiana tabacum L.) cultivars.

Tobacco (Nicotiana tabacum L.) is a potential phytoremediator that can reduce soil cadmium (Cd) contamination. Pot and hydroponic experiments were conducted to investigate the difference in absorption kinetics, translocation patterns, accumulation capacity, and extraction amounts between two leading tobacco cultivars in China. We studied the chemical forms and subcellular distribution of Cd in the plants to understand the diversity of the detoxification mechanism of the cultivars. The concentration-dependent kinetics of Cd accumulation in leaves, stems, roots, and xylem sap for cultivars Zhongyan 100 (ZY100) and K326, fitted well with the Michaelis-Menten equation. K326 exhibited high biomass, Cd tolerance, Cd translocation, and phytoextraction abilities. The acetic acid, sodium chloride, and water-extractable fractions accounted for > 90% of Cd in all ZY100 tissues but only in K326 roots and stems. Moreover, the acetic acid and NaCl fractions were the predominant storage forms, while the water fraction was the transport form. The ethanol fraction also contributed significantly to Cd storage in K326 leaves. As the Cd treatment increased, more NaCl and water fractions were found in K326 leaves, while only NaCl fractions increased in ZY100 leaves. For subcellular distribution, > 93% Cd proportions were primarily stored in both cultivars' soluble or cell wall fraction. The proportion of Cd in the cell wall fraction of ZY100 roots was less than that of K326, while that proportion in the soluble fraction in ZY100 leaves was higher than in K326 leaves. These findings demonstrate that Cd accumulation patterns, detoxification, and storage strategies differ between the cultivars, providing a deeper understanding of Cd tolerance and accumulation mechanism in tobacco plants. It also guides the screening of germplasm resources or gene modification to improve the Cd phytoextraction efficiency of tobacco.

Evaluation of pH-Dependent Metal Speciation Artifacts in Whole-Cell Bioreporter Analysis.

Whole-cell bacterial biosensors (bioreporters) are commonly applied for determination of metal toxicity and bioavailability in environmental samples. This is accomplished using a standard procedure whereby the sample is mixed with bioreporter cells suspended in a buffered medium at a fixed pH (set-point pH assay). This experimental approach can alter the sample pH. We therefore hypothesized that metal speciation artifacts compromising our ability to use bioreporters for determination of the "true" metal bioavailability in environmental samples may be introduced. Using the copper-specific bioreporter DF57-Cu15 as a model, we compared the conventional set-point pH assay to a flexible pH assay allowing for bioavailability determination at in situ sample pH. Our results demonstrate that pH-dependent metal speciation bias may occur when using the conventional set-point pH assay, and we recommend performing bioreporter measurements and calibrations at in situ sample pH. Although we only studied copper bioavailability, our results also have implications for bioreporter determination of other analytes displaying pH-dependent speciation such as other metals and some organics. We call for additional bioreporter studies of chemical speciation artifacts as this represents a problem hitherto overlooked in bioreporter literature. We thus conclude that there may be considerable scope for optimization of existing bioreporter assays for assessment of environmental pollutant bioavailability.

Comparison of Metals and Tetracycline as Selective Agents for Development of Tetracycline Resistant Bacterial Communities in Agricultural Soil.

Environmental selection of antibiotic resistance may be caused by either antibiotic residues or coselecting agents. Using a strictly controlled experimental design, we compared the ability of metals (Cu or Zn) and tetracycline to (co)select for tetracycline resistance in bacterial communities. Soil microcosms were established by amending agricultural soil with known levels of Cu, Zn, or tetracycline known to represent commonly used metals and antibiotics for pig farming. Soil bacterial growth dynamics and bacterial community-level tetracycline resistance were determined using the [3H]leucine incorporation technique, whereas soil Cu, Zn, and tetracycline exposure were quantified by a panel of whole-cell bacterial bioreporters. Tetracycline resistance increased significantly in soils containing environmentally relevant levels of Cu (≥365 mg kg-1) and Zn (≥264 mg kg-1) but not in soil spiked with unrealistically high levels of tetracycline (up to 100 mg kg-1). These observations were consistent with bioreporter data showing that metals remained bioavailable, whereas tetracycline was only transiently bioavailable. Community-level tetracycline resistance was correlated to the initial toxicant-induced inhibition of bacterial growth. In conclusion, our study demonstrates that toxic metals in some cases may exert a stronger selection pressure for environmental selection of resistance to an antibiotic than the specific antibiotic itself.

Heavy Metal Leaching as Affected by Long-Time Organic Waste Fertilizer Application.

The recycling of urban waste products as fertilizers in agriculture may introduce contaminants such as heavy metals into soil that may leach and contaminate groundwater. In the present study, we investigated the leaching of heavy metals from intact soil cores collected in the long-term agricultural field trial CRUCIAL. At the time of sampling, the equivalent of >100 yr of urban waste fertilizers following Danish legislation had been applied. The leaching of Cu was significantly increased in the treatments receiving organic waste products compared with the unfertilized control but remained below the permissible level following Danish drinking water guidelines. The leaching of Cu was controlled primarily by the topsoil Cu content and by the leaching of dissolved organic carbon (DOC) but at the same time significantly correlated with leaching of colloids in soils that had not received fertilizer or had received an organic fertilizer with a low concentration of Cu. The leaching of Zn, Cd, and Co was not significantly increased in urban waste-fertilized treatments. The leaching of Mo was elevated in accelerated waste treatments (both agricultural and urban), and the leaching of Mo was linked to the leaching of DOC. Since leaching of Cr and Pb was strongly linked to the level of colloid leaching, leaching of these metals was reduced in the urban waste treatments. Overall, the results presented should not raise concern regarding the agricultural use of urban waste products in agriculture as long as the relevant guidelines are followed.

Method for assessment of stormwater treatment facilities - Synthetic road runoff addition including micro-pollutants and tracer.

Stormwater treatment facilities (STFs) are becoming increasingly widespread but knowledge on their performance is limited. This is due to difficulties in obtaining representative samples during storm events and documenting removal of the broad range of contaminants found in stormwater runoff. This paper presents a method to evaluate STFs by addition of synthetic runoff with representative concentrations of contaminant species, including the use of tracer for correction of removal rates for losses not caused by the STF. A list of organic and inorganic contaminant species, including trace elements representative of runoff from roads is suggested, as well as relevant concentration ranges. The method was used for adding contaminants to three different STFs including a curbstone extension with filter soil, a dual porosity filter, and six different permeable pavements. Evaluation of the method showed that it is possible to add a well-defined mixture of contaminants despite different field conditions by having a flexibly system, mixing different stock-solutions on site, and use bromide tracer for correction of outlet concentrations. Bromide recovery ranged from only 12% in one of the permeable pavements to 97% in the dual porosity filter, stressing the importance of including a conservative tracer for correction of contaminant retention values. The method is considered useful in future treatment performance testing of STFs. The observed performance of the STFs is presented in coming papers.

Unraveling the Complex Behavior of AgNPs Driving NP-Cell Interactions and Toxicity to Algal Cells.

While the importance of nanoparticle (NP) characterization under relevant test conditions is widely recognized in nanotoxicology, few studies monitor NPs behavior in the presence of exposed organisms. Here we studied the behavior of nine types of silver nanoparticles (AgNPs) during the 48 h algal toxicity test. In particular, we investigated NP aggregation and dissolution by time-resolved inductively coupled plasma mass spectrometry and ultrafiltration and performed mass balance measurements to study the distribution of Ag in the test system. We also determined the amount of extra- and intracellular Ag by chemically etching AgNPs on the surface of algal cells and used dark field microscopy for their imaging. We observed that positively charged branched polyethilenimine (bPEI)-coated AgNPs tend to aggregate in the presence of algae and interact with test vessels and algal cells, while citrate-coated AgNPs have a tendency to dissolve. On the other hand, with large variation of half-maximum effective concentration (EC50) across tested NPs (5.4 to 300 ngAg mL-1), Ag internalized by the algal cells at EC50 was similar (0.8 to 3.6 ngAg mL-1) for all AgNP types. These data show that while sorption to the vessels, dissolution, and aggregation impact on the distribution of AgNPs in the test system and on interactions with algal cells, AgNP toxicity is strongly correlated with the NP-cell surface interaction and internalization of Ag.

Aluminum Oxide-Coated Sand for Improved Treatment of Urban Stormwater.

Infiltration facilities for urban stormwater runoff, such as biofilters, rain gardens, and curb extensions, typically contain an engineered soil mixture for effective drainage and retention of pollutants. The treatment efficiency of such soils is generally considered high for many pollutants. However, recent studies have revealed that in situ mobilization of soil organic matter may cause leaching of a range of pollutants and therefore diminish the long-term performance of engineered soils. The purpose of this study was to develop and test sand coated with aluminum (Al) oxides for improving the retention of organic matter and a range of common pollutants in engineered soils. Two alternative Al-coating methods were successfully developed in the laboratory. The Al coating of the sand increased the specific surface area from 0.3 to 1.1 m g to 0.87 to 2.2 m g depending on sand fraction. One method was upscaled to produce 100 kg coated sand. The stability of the coatings was studied in batch experiments. Dry shaking showed a high resistance of the coating against mechanical stress. Increasing the ionic strength by the addition of NaCl seemed to improve the stability of the coatings. Varying pH showed that acidic conditions could compromise the Al coating stability. Overall, one coating method showed slightly better results in terms of higher surface area and stability. The Al coating significantly improved the retention capacity of the sand toward dissolved organic carbon. The results document that it is possible to coat sand effectively with Al oxides and consequently to improve the retention capacity and lifetime of engineered soils for urban stormwater management.

Diffusive Gradients in Thin Films as a Reference Method for Assessing Soil Phosphorus by Visual and Near-Infrared Spectroscopy.

Phosphorus (P) deficiency is a severe challenge in many agricultural areas around the globe, while at the same time, aquatic environments are threatened by leaching and runoff of excess P in other areas. Accurate, cheap, and rapid assessment of crop P needs and risk of P loss is therefore necessary to optimize the use of P fertilizer worldwide. The purpose of this study was to develop a method to predict soil P concentrations by visual and near-infrared spectroscopy using reference P concentrations determined by diffusive gradients in thin films (DGT); Olsen P results were included for comparison. The study was conducted on paddy soils from six main rice-producing ( L.) provinces in southern China. Using DGT P as a reference resulted in a better visual and near-infrared calibration to predict soil P concentrations, as compared with using Olsen P.

Land management of bracken needs to account for bracken carcinogens--a case study from Britain.

Bracken ferns are some of the most widespread ferns in the World causing immense problems for land managers, foresters and rangers. Bracken is suspected of causing cancer in Humans due to its content of the carcinogen ptaquiloside. Ingestion of bracken, or food and drinking water contaminated with ptaquiloside may be the cause. The aim of this study was to monitor the content of ptaquiloside in 20 bracken stands from Britain to obtain a better understanding of the ptaquiloside dynamics and to evaluate the environmental implications of using different cutting regimes in bracken management. The ptaquiloside content in fronds ranged between 50 and 5790 µg/g corresponding to a ptaquiloside load in the standing biomass of up to 590 mg/m(2) in mature fronds. Ptaquiloside was also found in the underground rhizome system (11-657 µg/g) and in decaying litter (0.1-5.8 µg/g). The amount of ptaquiloside present in bracken stands at any given time is difficult to predict and did not show any correlations with edaphic growth factors. The content of ptaquiloside turned out to be higher in fronds emerging after cutting compared to uncut fronds. Environmental risk assessment and bracken management must therefore be based on actual and site specific determinations of the ptaquiloside content. Care must be taken to avoid leaching from cut ferns to aquifers and other recipients and appropriate precautionary measures must be taken to protect staff from exposure to bracken dust.

Copper use and accumulation in catfish culture in the Mekong Delta, Vietnam.

Aquaculture of Pangasius hypophthalmus (striped catfish) in Vietnam reached 1.1 million tonnes in 2011 and catfish fillets are exported worldwide. The intensive cultures of catfish mainly in earth ponds have made it necessary to apply CuSO4 and other chemicals to control external parasites and other pathogens. However, accumulation of Cu in aquaculture ponds may pose a hazard to growth of fish or to the aquatic environment. The aim of this study was to determine accumulation of Cu in sediment, water and fish in a catfish pond with a history of repeated treatment with CuSO4 in the Mekong Delta, Vietnam. Copper concentrations in pond sediment were in the interval 21.3-45.7 mg kg(-1) dw and did not exceed the Vietnamese values for soil to be used for agricultural production (70 mg kg(-1) dw.). During three samplings the total mean concentration of Cu in pond water (4 µg L(-1)) did not exceed the LC50-value (70 µg L(-1)) for catfish and the mean dissolved concentration of Cu (0.986 µg L(-1)) did not seem to constitute a risk for the stability of the aquatic ecosystem. No significant variation in Cu concentrations between sampling sites in the pond and depth of sediment profile were determined. The accumulation of Cu in catfish was highest in the liver compared to the skin, gills and muscle tissue. With the current practice of removing pond sludge three to four times during a production cycle little if any Cu seems to accumulate in catfish ponds despite repeated anti-parasite treatments with CuSO4. Further studies are needed to assess the eco-toxicity and impact on agricultural production when pond sediment is discharged into aquatic recipients and used as soil fertilizer.

Co-cropping vetiver grass and legume for the phytoremediation of an acid mine drainage (AMD) impacted soil.

Acid mine drainage (AMD) is a form of environmental pollution from mining activity that can negatively affect soil environments by acidification, salinisation, and metal(loid) contamination. The use of plants to remediate (phytoremediation) these impacted environments while generating plant-based value is a promising approach to more accessible and cost-benefiting restoration of post-mining, marginal lands. In this study, a 3-month growth-chamber pot experiment was conducted to investigate the influence of co-cropping two plant species, Chrysopogon zizanioides (vetiver grass) and the legume Medicago truncatula (barrel clover) with a wheat straw biochar amendment on the phytostabilisation of metal(loid)s Cr, Zn, and As and the phytoextraction of rare earth element (REE) in an AMD impacted soil from a gold mining region in South Africa. The results showed that co-cropping with vetiver significantly lowered the legume's Cr, Zn, and As root contents by 80%, 32% and 54%, respectively, and improved the plant's overall metal(loid) tolerance by increasing its translocation from root to shoot tissue. The biochar further inhibited root uptake of Cr and Zn, by 71% and 36%, and increased the legume biomass by 40%. Both plant species and cropping treatments exhibited low REE extraction capabilities by shoot tissue, which accounted for less than 0.2% of total soil REE contents. The study shows that co-cropping with vetiver and biochar amendment are effective tools for the phytoremediation of AMD impacted soil mainly by lowering plant uptake and improving plant metal(loid) tolerance. Likely mechanisms at play include the alteration of rhizosphere chemistry and species-specific physiological and molecular responses. These effects offer support for the phytostabilisation of AMD impacted soil with the generation of plant-based value through dual (and safe) cultivation (phytoprotection) rather than through REE recovery from plant biomass (phytoextraction). These techniques could allow for the simultaneous restoration of post-mining, mining-impacted and marginal lands with agricultural production.

Assessment of the stabilization effect of ferrous sulfate for arsenic-contaminated soils based on chemical extraction methods and in vitro methods: Methodological differences and linkages.

Stabilization of arsenic-contaminated soils with ferrous sulfate has been reported in many studies, but there are few stabilization effects assessments simultaneously combined chemical extraction methods and in vitro methods, and further explored the corresponding alternative relationships. In this study, ferrous sulfate was added at FeAs molar ratio of 0, 5, 10 and 20 to stabilize As in 10 As spiked soils. Stabilization effects were assessed by 6 chemical extraction methods (toxicity characteristic leaching procedures (TCLP), HCl, diethylenetriamine pentaacetic acid (DTPA), CaCl2, CH3COONH4, (NH4)2SO4), and 4 in vitro methods (physiologically based extraction test (PBET), in vitro gastrointestinal method (IVG), Solubility Bioaccessibility Research Consortium (SBRC) method, and the Unified Bioaccessibility Research Group of Europe method (UBM)). The results showed that the HCl method provides the most conservative assessment results in non-calcareous soils, and in alkaline calcareous soils, (NH4)2SO4 method provides a more conservative assessment. In vitro methods provided significantly higher As concentrations than chemical extraction methods. The components of the simulated digestion solution as well as the parameters may have contributed to this result. The small intestinal phase of PBET and SBRC method produced the highest and lowest ranges of As concentrations, and in the range of 127-462 mg/kg and 68-222 mg/kg when the FeAs molar ratio was 5. So the small intestinal phase of PBET method may provide the most conservative assessment results, while the same phase of SBRC may underestimate the human health risks of As in stabilized soil by 51 %(at a FeAs molar ratio of 5). Spearman correlation analysis indicated that the small intestinal phase of PBET method correlated best with HCl method (correlation coefficient: 0.71). This study provides ideas for the assessment of stabilization efforts to ensure that stabilization meets ecological needs while also being less harmful to humans.

The use of elements as a substitute for biomass in toxicokinetic studies in small organisms.

Determining pollutant concentrations in the tissues of experimental test organisms is necessary for understanding uptake and excretion mechanisms of toxicants. Using small organisms can make the determination of organism biomass inaccurate. We here propose the use of selected tissue element contents as a proxy for tissue biomass. Forty different elements were determined in tissues of the two worm species Enchytraeus crypticus and Caenorhabditis elegans derived from cultures exposed to combinations of varying temperatures and sublethal concentrations of Cu and Cd. Three criteria were used to select good biomass indicators: The element concentration must (1) be present in concentrations above the limit of quantification of the analytical method, (2) must be stable and (3) must not be affected by the treatment. If the organisms are believed to have significant amounts of soil in their gut, the element must also be present at higher concentrations in the tissue compared to the soil. The three elements K, Mg and P all lived up to the first three criteria for both worm species, showing correlation coefficients between element content and tissue biomass of 0.97, 0.96 and 0.97 (n = 25) and 0.997, 0.998 and 0.992 (n = 10) for K, Mg and P in the E. crypticus and C. elegans, respectively. Only P would be an appropriate biomass indicator for organisms with a soil gut uptake assuming the tissue concentrations in soil eating organisms are similar to those measured in the present study. Using Mg as a biomass indicator on a verification dataset of Cu and Cd uptake in E. crypticus, compared to giving Cu and Cd content per individual organism, decreased the coefficient of variation from 31 ± 21 to 21 ± 17 % and from 34 ± 22 to 9.3 ± 6.4 % for tissue Cu and Cd, respectively. We therefore conclude that the use of an element as a biomass indicator can reduce tissue concentration variability.

Composition, Flavor, Chemical Foodsafety, and Consumer Preferences of Bottled Water.

The worldwide consumption of bottled water has experienced an annual increase of 5.5% since 2004 and different authors have speculated that this is due to beliefs of superior flavor and health qualities of bottled water over tap water. The content of certain minerals varies by 2 to 6 orders of magnitude between bottled water brands. The major cations Ca, Mg, Na, and K can be found in concentrations up to 730, 450, 1900, and 270 mg/L but are usually below 100 mg/L; higher concentrations have only been found in some European and North American bottled water samples. The dominating anions are HCO3 - , Cl- , and SO4 2- . Sensory evaluation and description of water strongly depend on personal preferences and sensitivities. The major cations can be detected by taste in concentrations down to 2 digits in the mg/L range; however, the intensity depends on which anions are present. Most cations add different degrees of salty, sour, sweet, and bitter tastes to water depending on their concentrations. Al, Ca, Cu, Fe, Mg, and Zn may introduce metallic, astringent, and irritative sensations and for Fe and Cu also retro-nasal odors may influence the metallic sensation. Drinking water with total dissolved solids in the range of 100 to 400 mg/L results in good sensory quality. Known off-flavor problems originate from by-products of ozonation and leaching of organics from bottling material which may also be enhanced by ozonation, and microbial by-products from the source water such as geosmin and 2-methylisoborneol, lubricants, or cleaning agents used in the bottling industry.

Pollution and potential mobility of Cd, Ni and Pb in the sediments of a wastewater-receiving river in Hanoi, Vietnam.

Large quantities of untreated industrial and domestic wastewater are discharged from the city of Hanoi into urban rivers. Sediment samples from three sites in the To Lich River in Hanoi were assessed with respect to the concentrations and potential mobility of cadmium (Cd), nickel (Ni) and lead (Pb). Due to very high Cd concentrations up to 700 mg kg(-1) at one site, the sediment was considered highly unsuitable for any types of land use if dredged and disposed of on land. Chemical sequential extractions of wet and anoxic sediment samples showed that Cd and Pb were largely associated with the redox-sensitive fractions and could thus be mobilised following measures such as resuspension or dredging. To assess the potential mobilisation of heavy metals from the anoxic sediment due to oxidation, the samples were exposed to different oxidants (i.e. atmospheric air and hydrogen peroxide) and afterwards submitted to a leaching test. These experiments showed that although oxidation may increase the equilibrium pore water concentrations of heavy metals in the sediments, other sediment mineral fractions seem to effectively immobilise heavy metals potentially released from the oxidisable fraction.

Impacts of biochar materials on copper speciation, bioavailability, and toxicity in chromated copper arsenate polluted soil.

Trace element polluted soils pose risks to human and environmental health. Biochar can decrease trace element bioavailability in soils, but their resulting ability to reduce soil toxicity may vary significantly depending on feedstocks used, pyrolysis conditions, and the target pollutants. Chromated copper arsenate (CCA) polluted sites are common, but only very few types of biochar have been tested for these sites. Hence, we tested fourteen well-characterized biochar materials for their ability to bind Cu and reduce toxicity in a CCA polluted soil in a 56-day experiment. Biochar (1%, wt/wt) increased plant (wheat, Triticum aestivum L.) shoot and root growth by 6-58% and 0-73%, reduced soil toxicity to Arthrobacter globiformis by 7-55%, decreased bioavailable Cu (Pseudomonas fluorescens bioreporter) by 5-65%, and decreased free Cu2+ ion activities by 27-89%. The A. globiformis solid-contact test constituted a sensitive ecotoxicological endpoint and deserves further attention for assessment of soil quality. Oil seed rape straw biochar generally performed better than other tested biochar materials. Biochar performance was positively correlated with its high cation exchange capacity, multiple surface functional groups, and high nitrogen and phosphorus content. Our results pave the way for future selection of feedstocks for creation of modified biochar materials with optimal performance in CCA polluted soil.

Phosphorus doped cyanobacterial biochar catalyzes efficient persulfate oxidation of the antibiotic norfloxacin.

In this study, cyanobacterial biochars (CBs) enriched/doped with non-metallic elements were prepared by pyrolysis of biomass amended with different N, S, and P containing compounds. Their catalytic reactivity was tested for persulfate oxidation of the antibiotic norfloxacin (NOR). N and S doping failed to improve CB catalytic reactivity, while P doping increased reactivity 5 times compared with un-doped biochar. Biochars produced with organic phosphorus dopants showed the highest reactivity. Post-acid-washing improved catalytic reactivity. In particular, 950 ℃ acid-washed triphenyl-phosphate doped CB showed the largest degradation rate and reached 79% NOR mineralization in 2 h. Main attributes for P-doped CBs high reactivity were large specific surface areas (up to 655 m2/g), high adsorption, high C-P-O content, graphitic P and non-radical degradation pathway (electron transfer). This study demonstrates a new way to reuse waste biomass by producing efficient P-doped metal-free biochars and presents a basic framework for designing carbon-based catalysts for organic pollutant degradation.

Selection for Cu-tolerant bacterial communities with altered composition, but unaltered richness, via long-term Cu exposure.

Toxic metal pollution affects the composition and metal tolerance of soil bacterial communities. However, there is virtually no knowledge concerning the responses of members of specific bacterial taxa (e.g., phyla or classes) to metal toxicity, and contradictory results have been obtained regarding the impact of metals on operational taxonomic unit (OTU) richness. We used tag-coded pyrosequencing of the 16S rRNA gene to elucidate the impacts of copper (Cu) on bacterial community composition and diversity within a well-described Cu gradient (20 to 3,537 µg g(-1)) stemming from industrial contamination with CuSO(4) more than 85 years ago. DNA sequence information was linked to analysis of pollution-induced community tolerance (PICT) to Cu, as determined by the [(3)H]leucine incorporation technique, and to chemical characterization of the soil. PICT was significantly correlated to bioavailable Cu, as determined by the results seen with a Cu-specific bioluminescent biosensor strain, demonstrating a specific community response to Cu. The relative abundances of members of several phyla or candidate phyla, including the Proteobacteria, Bacteroidetes, Verrumicrobia, Chloroflexi, WS3, and Planctomycetes, decreased with increasing bioavailable Cu, while members of the dominant phylum, the Actinobacteria, showed no response and members of the Acidobacteria showed a marked increase in abundance. Interestingly, changes in the relative abundances of classes frequently deviated from the responses of the phyla to which they belong. Despite the apparent Cu impacts on Cu resistance and community structure, bioavailable Cu levels did not show any correlation to bacterial OTU richness (97% similarity level). Our report highlights several bacterial taxa responding to Cu and thereby provides new guidelines for future studies aiming to explore the bacterial domain for members of metal-responding taxa.

Contents and mass balances of cadmium and arsenic in a wastewater-fed fish pond of Hoang Mai, Hanoi, Vietnam.

Wastewater-fed aquatic production has been practiced since the 1960s in peri-urban Hanoi. Wastewater is used as a cheap and reliable source of both water and nutrients but there is a risk that it may lead to accumulation of potentially toxic elements (PTEs) in the production systems and produce and thereby constitute a food safety risk. This study investigates the cadmium (Cd) and arsenic (As) concentrations in water, sediment, plant and fish of a wastewater fed-fish pond in Hoang Mai district, Hanoi, Vietnam. Cd concentrations in the water were lower than the Vietnamese quality guidelines (0.8-1.8 µg Cd/L) for protection of aquatic life but As concentrations in inlet and outlet water of 44.3 and 21.3 µg/L, respectively both were higher that the guidelines (20 µg As/L) and may cause toxicity to fish in the pond and the surrounding vegetable farms using the outlet water for irrigation. The concentrations of Cd and As in fish and Cd in water spinach did not constitute a food safety risk. However, As concentrations in water spinach may be of concern. A mass balance estimate for the fish pond showed that about 12% of the incoming As accumulate in suspended particular matters, 40% settle down to the sediment, less than 0.1% accumulate in the fish and water spinach and 48% overflow with the pond effluent. The concentrations of Cd were too low to make a mass balance for the fish pond.