RESUMEN
Dibromoethane is a widespread, persistent organic pollutant. Biochars are known mediators of reductive dehalogenation by layered FeII-FeIII hydroxides (green rust), which can reduce 1,2-dibromoethane to innocuous bromide and ethylene. However, the critical characteristics that determine mediator functionality are lesser known. Fifteen biochar substrates were pyrolyzed at 600 °C and 800 °C, characterized by elemental analysis, X-ray photo spectrometry C and N surface speciation, X-ray powder diffraction, specific surface area analysis, and tested for mediation of reductive debromination of 1,2-dibromoethane by a green rust reductant under anoxic conditions. A statistical analysis was performed to determine the biochar properties, critical for debromination kinetics and total debromination extent. It was shown that selected plant based biochars can mediate debromination of 1,2-dibromoethane, that the highest first order rate constant was 0.082/hr, and the highest debromination extent was 27% in reactivity experiments with 0.1 µmol (20 µmol/L) 1,2-dibromoethane, ≈ 22 mmol/L FeIIGR, and 0.12 g/L soybean meal biochar (7 days). Contents of Ni, Zn, N, and P, and the relative contribution of quinone surface functional groups were significantly (p < 0.05) positively correlated with 1,2-dibromoethane debromination, while adsorption, specific surface area, and the relative contribution of pyridinic N oxide surface groups were significantly negatively correlated with debromination.
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Carbón Orgánico , Carbón Orgánico/química , Halogenación , Oxidación-Reducción , Dibromuro de Etileno/química , Modelos QuímicosRESUMEN
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 â¼10 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.
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Álcalis , Arsénico , Agua Subterránea , Aguas del Alcantarillado , Aguas del Alcantarillado/química , Agua Subterránea/química , Álcalis/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Compuestos Férricos/químicaRESUMEN
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.
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Arsénico , Compuestos Ferrosos , Contaminantes del Suelo , Humanos , Arsénico/análisis , Contaminantes del Suelo/análisis , Contaminación Ambiental/análisis , Suelo , Disponibilidad BiológicaRESUMEN
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.
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Chrysopogon , Fabaceae , Contaminantes del Suelo , Biodegradación Ambiental , Suelo/química , Oro , Ácidos , Verduras , Contaminantes del Suelo/análisisRESUMEN
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 â 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.
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Antibacterianos , Cianobacterias , Norfloxacino , Fósforo , Carbón OrgánicoRESUMEN
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.
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Contaminantes del Suelo , Oligoelementos , Humanos , Cobre/toxicidad , Disponibilidad Biológica , Contaminantes del Suelo/metabolismo , Carbón Orgánico , Suelo , Triticum/metabolismoRESUMEN
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.
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Cadmio , Contaminantes del Suelo , Nicotiana , Cinética , Cloruro de Sodio/farmacología , Raíces de Plantas , Xilema , Hojas de la PlantaRESUMEN
Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10-2 min-1 m-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, â¢OH and SO4â¢- radicals in low PT CBs/PDS systems, where the presence of MnII promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.
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Antibacterianos , Norfloxacino , Catálisis , Carbón OrgánicoRESUMEN
Acid mine drainage (AMD), a waste product of mining activities containing sulfates, iron and heavy metals, causes severe environmental degradation and pose risks to human health and sustainable development. Areas impacted by AMD are lacking remediation techniques that holistically address the ecologic, social, and economic needs of affected communities, for which phytoremediation is a promising solution. This review article introduces AMD and AMD-impacted environments and critically discusses phytomanagement, phytoprotection, and phytorestoration approaches towards AMD-impacted environments. Continued research and application of such approaches will help optimize resource and revenue-generating potentials, address biodiversity loss and carbon storage concerns of climate change, and promote sustainable agricultural management. With a focus on energy crops, phytomining critical elements, carbon storage, co-cropping, allelopathy, and ecosystem restoration, this review examines phytoremediation research that addresses positive economic and environmental opportunities for AMD-impacted environments.
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Metales Pesados , Contaminantes Químicos del Agua , Ácidos , Biodegradación Ambiental , Ecosistema , Humanos , Minería , Contaminantes Químicos del Agua/análisisRESUMEN
The heavy metals, including cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), zinc (Zn), and the metalloid arsenic (As) were detected in surface and core soil samples collected from a tobacco growing region in Shandong Peninsula on the east coast of China to evaluate their pollution levels, ecological and health risks, and to analyze their spatial and vertical distributions. The heavy metal sources were identified quantitatively using the positive matrix factorization (PMF) receptor model. In accordance, most of the soils did not have accumulations and were not contaminated by As, Cr, Cu, Ni, Pb, and Zn. High accumulations of Cd and Hg occurred in the soils, posing an ecological risk to the local agricultural environment, while Cr and Ni levels presented a carcinogenic health risk to humans. Four main sources of heavy metals in the soils were identified. Correspondingly Ni and Cr were mainly originated from natural sources, Hg from coal combustion, Cd from agricultural practices, Cu, Pb, and Zn from agricultural practices and industrial activities, and As from industrial activities.
RESUMEN
Industrial by-products provide materials for remediation measures. In this study, a silicon-iron amendment was prepared from residue originating from acid-extracted copper (Cu) tailings based on thermal activation at temperatures ranging from 550⯰C to 1150⯰C for 30â¯min with the use of additives (CaO, Na2CO3, NaOH). The remediation performance of the amendment was evaluated through soil incubation and greenhouse pot experiments with vetiver (Vetiveria zizanioides). The results showed that the highest levels of soluble Si (6.11% of the total Si) and Fe (2.3% of the total Fe) in the amendment were achieved with thermal activation at 1150⯰C for 30â¯min using an optimal ratio between residue and additives (residue: CaO: Na2CO3: NaOHâ¯=â¯1: 0.4: 0.4: 0.2). Heavy metal release indicated that the amendment could be safely used for soil remediation. The incubation experiments showed that the DTPA-extractable Cd, Cr and Pb in contaminated soils decreased with increasing amendment rate, which was not observed for As. The amendment-induced decrease in the Cd, Cr and Pb availability in contaminated soils could be explained by pH-change induced immobilization, Fe-induced chemisorption, Si-induced co-precipitation, and Ca-induced ion exchange. Correlation analysis suggested that there were significant negative correlations between DTPA-extractable Cd, Cr and Pb and the pH, Fe, Si, and Ca in soil pore water and soil. The most suitable amendment rate was determined to be 1% by balancing the efficacy and wise utilization of the amendment. The pot experiment demonstrated that the amendment promoted the vetiver growth and stimulated the accumulation of Cd and Cr in the roots. The amendment was proved to be promising for the phytostabilization of Cd, Cr and Pb in contaminated soils. Further investigations are required to determine whether the amendment is a tool for the long-term remediation of multi-metal-contaminated soils at the field scale.
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Restauración y Remediación Ambiental/métodos , Metales Pesados/química , Contaminantes del Suelo/química , Ácidos , Cobre/análisis , Contaminación Ambiental/análisis , Hierro/análisis , Metales Pesados/análisis , Minería , Silicio/análisis , Suelo/química , Contaminantes del Suelo/análisisRESUMEN
Few plant species used for revegetation grow well in multi-metal-contaminated soils. Vetiver grass (Vetiveria zizanioides) is known to be tolerant of heavy metals. Vetiver has been reported to be effective for revegetation and heavy metal phytoextraction by applying targeted amendments due to its large biomass. In this study, a greenhouse vetiver pot experiment and soil incubation were performed to investigate the growth and Cd, Cr, Cu, Pb, and Zn uptake of vetiver grown in multi-metal-contaminated soils treated with a CaO-activated Si-based slag amendment (0, 0.5, 1.0, and 2.0% w/w). The results showed that the effects of slag amendment on plant growth and heavy metal uptake and distribution were dependent on the amendment dosages and metal species. Although vetiver could grow in contaminated soils, its growth was obviously inhibited. The slag amendment enhanced the vetiver growth and the highest biomass (2.62-fold over the control) was determined at a 1.0% amendment rate. The slag amendment improved plant growth by alleviating the toxicity of heavy metals in plants. This result was mainly attributed to the increases in soil pH and citric acid-extractable Si caused by alkaline amendment. The results suggest that vetiver can be applied to remediate multi-metal-contaminated soils in conjunction with the application of CaO-activated Si-based slag amendment.
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Chrysopogon/crecimiento & desarrollo , Metales Pesados/análisis , Silicio/química , Metales Pesados/química , Suelo , Contaminantes del Suelo/análisisRESUMEN
This study evaluates the results of the characterization of air pollution in urban green areas using edible plants. To this purpose, we examined the effect of location (i.e., three different levels of pollution), substrate (peat moss and vermiculite), and plant species (oilseed rape [ L.] and kale [ L.]) on the accumulation of trace elements on leaves. A total of 36 samples of unwashed leaves were digested with HNO-HO and analyzed for 27 elements by inductively coupled plasma mass spectrometry. Considering the location, plants exposed next to the road showed higher contents of traffic-related elements, and additionally, outdoors samples were enriched in marine aerosol ions. Cadmium and Pb concentrations did not exceed the European legal maximum levels for vegetables, so their consumption would be safe for human health. Results support the hypothesis that edible plants such as kale and rapeseed could be used as bioindicators of atmospheric pollution.
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Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Jardines , Oligoelementos/análisis , Contaminación del Aire/estadística & datos numéricos , Atmósfera/química , Hojas de la PlantaRESUMEN
Metals are among the most toxic pollutants in urban stormwater. To investigate the concentration of dissolved and particulate fractions, the temporal variation during rain events, the effect of wash-off surface, and to assess the pollution status of metals in urban runoff, a total of 155 samples were collected mainly from trafficked areas, roofs and parking lots in Beijing from March to November 2015. Most of the metals were found mainly in the particulate fraction (68-96%) from trafficked surfaces, while for roof runoff Cd, Fe, Mn and Zn were found more equally in dissolved and particulate fractions. Metal concentrations were higher during start of a rain event than later (pâ¯<â¯0.05), and also were higher the longer the period of antecedent dry days. The mean concentration of all metals in trafficked areas exceeded both the Chinese standard Level III (swimming and fishery waters) and the European standards (surface water). Mean concentrations of Cd, Mn, Zn, Al, Fe, Pb and Ni from trafficked areas were 2-10 times higher due to higher traffic intensity and substantial atmospheric deposition, while Sb was 20 times higher than in any other reported data for urban runoff. Cluster analysis (CA) and principal component analysis (PCA) together with Pearson's correlation co-efficient suggested that Cd, Cr, Cu, Mn, Ni, Pb, and Zn mainly originates from vehicular activities, while Mn and Zn in roof runoff is due to atmospheric deposition. The geo-accumulation and pollution indices show that runoff from trafficked areas are moderately to heavily polluted by most metals, except Cu and Zn. Thus, Beijing urban runoff presents an environmental risk towards lakes, bathing water and drinking water. The results can be used as basis for development of stormwater and pollution control strategies.
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Monitoreo del Ambiente/métodos , Metales Pesados/análisis , Material Particulado/análisis , Lluvia/química , Contaminantes Químicos del Agua/análisis , Beijing , UrbanizaciónRESUMEN
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.
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Monitoreo del Ambiente , Contaminantes Ambientales , Artefactos , Cobre , Concentración de Iones de HidrógenoRESUMEN
The physico-chemical factors affecting the distribution, behavior and speciation of chromium (Cr), copper (Cu) and arsenic (As) was investigated at a former wood impregnation site (Fredensborg, Denmark). Forty soil samples were collected and extracted using a sequential extraction technique known as the Chemometric Identification of Substrates and Element Distributions (CISED) and a multivariate statistical tool (redundancy analysis) was applied. CISED data was linked to water-extractable Cr, Cu and As and bioavailable Cu as determined by a whole-cell bacterial bioreporter assay. Results showed that soil pH significantly affected the solid phase distribution of all three elements on site. Additionally, elements competing for binding sites, Ca, Mg and Mn in the case of Cu, and P, in the case of As, played a major role in the distribution of these elements in soil. Element-specific distributions were observed amongst the six identified soil phases including residual pore salts, exchangeable, carbonates (tentative designation), Mn-Al oxide, amorphous Fe oxide, and crystalline Fe oxide. While Cr was strongly bound to non-extractable crystalline Fe oxide in the oxic top soil, Cu and notably, As were associated with readily extractable phases, suggesting that Cu and As, and not Cr, constitute the highest risk to environmental and human health. However, bioavailable Cu did not significantly correlate with CISED identified soil phases, suggesting that sequential extraction schemes such as CISED may not be ideally suited for inferring bioavailability to microorganisms in soil and supports the integration of receptor-specific bioavailability tests into risk assessments as a complement to chemical methods.
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Monitoreo del Ambiente , Metales Pesados/análisis , Contaminantes del Suelo/análisis , Arsénico , Bioensayo , Cromo , Cobre , Dinamarca , Contaminación Ambiental , Modelos Químicos , Medición de Riesgo , SueloRESUMEN
Chromated copper arsenates (CCA) have been extensively used as wood impregnation agents in Europe and North America. Today, CCA contaminated sites remain abundant and pose environmental risks that need to be properly managed. Using a TRIAD approach that combined chemical, ecotoxicological and ecological assessment of soil quality, we investigated the abilities of biochar and zero-valent iron (ZVI) to remediate CCA contaminated soil in a microcosm experiment. Soil samples from a highly contaminated CCA site (1364, 1662 and 540⯵gâ¯g-1 of As, Cu and Cr, respectively) were treated with two different biochars (fine and coarse particle size; 1% wâ¯w-1) and ZVI (5% wâ¯w-1), both as sole and as combined treatments, and incubated for 56â¯days at 15⯰C. In general, bioavailable As (Asbio) and Cu (Cubio) determined by whole-cell bacterial bioreporters corresponded well to water-extractable As and Cu (Aswater and Cuwater). However, in biochar treatments, only Cubio and not Cuwater was significantly reduced. In contrast, under ZVI treatments only Cuwater and not Cubio was reduced, demonstrating the value of complementing analytical with bacterial bioreporter measurements to infer bioavailability of elements to soil microorganisms. The combined fine particle size biochar and ZVI treatment effectively reduced water extractable concentrations of Cr, Cu, and As on site by 45%, 45% and 43% respectively, and led to the highest ecological recovery of the soil bacterial community, as measured using the [3H]leucine incorporation technique. We conclude that the combined application of biochar and ZVI as soil amendments holds promise for in-situ stabilization of CCA contaminated sites.
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Arseniatos/análisis , Carbón Orgánico/química , Hierro/química , Microbiología del Suelo , Contaminantes del Suelo/análisis , Suelo/química , Biodegradación Ambiental , Dinamarca , Monitoreo del Ambiente , MicrobiotaRESUMEN
BACKGROUND: It remains unclear whether adaptation and changes in diversity associated to a long-term perturbation are sufficient to ensure functional resilience of soil microbial communities. We used RNA-based approaches (16S rRNA gene transcript amplicon coupled to shotgun mRNA sequencing) to study the legacy effects of a century-long soil copper (Cu) pollution on microbial activity and composition, as well as its effect on the capacity of the microbial community to react to temporal fluctuations. RESULTS: Despite evidence of microbial adaptation (e.g., iron homeostasis and avoidance/resistance strategies), increased heterogeneity and richness loss in transcribed gene pools were observed with increasing soil Cu, together with an unexpected predominance of phage mRNA signatures. Apparently, phage activation was either triggered directly by Cu, or indirectly via enhanced expression of DNA repair/SOS response systems in Cu-exposed bacteria. Even though total soil carbon and nitrogen had accumulated with increasing Cu, a reduction in temporally induced mRNA functions was observed. Microbial temporal response groups (TRGs, groups of microbes with a specific temporal response) were heavily affected by Cu, both in abundance and phylogenetic composition. CONCLUSION: Altogether, results point toward a Cu-mediated "decoupling" between environmental fluctuations and microbial activity, where Cu-exposed microbes stopped fulfilling their expected contributions to soil functioning relative to the control. Nevertheless, some functions remained active in February despite Cu, concomitant with an increase in phage mRNA signatures, highlighting that somehow, microbial activity is still happening under these adverse conditions.
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Bacterias/virología , Bacteriófagos/aislamiento & purificación , Cobre/farmacología , Perfilación de la Expresión Génica/métodos , Metagenómica/métodos , Suelo/química , Bacterias/clasificación , Bacterias/genética , Bacteriófagos/genética , Cobre/química , Contaminación Ambiental , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Regulación Viral de la Expresión Génica/efectos de los fármacos , Filogenia , ARN Ribosómico 16S/genética , Estaciones del Año , Análisis de Secuencia de ARN/métodos , Microbiología del SueloRESUMEN
Greenhouse vegetable production (GVP) is the major type of vegetable production in China. However, dietary exposure of heavy metals through vegetable consumption has been identified as a potential risk to human health. To ensure safety of vegetables, soil threshold values (STVs) of cadmium (Cd) in GVP systems were assessed based on analysis of soil-vegetable Cd contents in relation to human health risk. Contents of Cd were determined in 324 sampled soil-vegetable pairs from five GVP systems in three Chinese provinces. Soil Cd contents ranged from 0.07 to 1.32â¯mgâ¯kg-1, with 17.9% of sampled soils exceeding current Chinese threshold values. Vegetable Cd contents ranged from 0.0003 to 0.546â¯mgâ¯kg-1, with 8.6% exceeding permissible maxima. Vegetable type and soil pH significantly affected Cd transfer from soil to vegetable with lower transfer at neutral (6.5â¯<â¯pHâ¯≤â¯7.5) to alkaline (pHâ¯>â¯7.5) soils and uptake decreasing in the order: Leafyâ¯>â¯rootstalkâ¯>â¯fruit. Consequently, both soil pH and vegetable type should be taken into consideration as suggested when revising current STVs for Cd in GVP systems in order to capture the health risk correctly and ensure safe vegetable consumption.
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Agricultura , Cadmio/análisis , Contaminantes del Suelo/análisis , Suelo/química , Verduras/química , China , Contaminación de Alimentos/análisis , Contaminación de Alimentos/estadística & datos numéricos , Frutas , Humanos , Metales Pesados/análisis , Hojas de la Planta/químicaRESUMEN
Intensive human activities, in particular agricultural and industrial production have led to heavy metal accumulation in the peri-urban agricultural soils of China threatening soil environmental quality and agricultural product security. A combination of spatial analysis (SA), Pb isotope ratio analysis (IRA), input fluxes analysis (IFA), and positive matrix factorization (PMF) model was successfully used to assess the status and sources of heavy metals in typical peri-urban agricultural soils from a rapidly developing region of China. Mean concentrations of Cd, As, Hg, Pb, Cu, Zn and Cr in surface soils (0-20â¯cm) were 0.31, 11.2, 0.08, 35.6, 44.8, 119.0 and 97.0â¯mgâ¯kg-1, respectively, exceeding the local background levels except for Hg. Spatial distribution of heavy metals revealed that agricultural activities have significant influence on heavy metal accumulation in the surface soils. Isotope ratio analysis suggested that fertilization along with atmospheric deposition were the major sources of heavy metal accumulation in the soils. Based on the PMF model, the relative contribution rates of the heavy metals due to fertilizer application, atmospheric deposition, industrial emission, and soil parent materials were 30.8%, 33.0%, 25.4% and 10.8%, respectively, demonstrating that anthropogenic activities had significantly higher contribution than natural sources. This study provides a reliable and robust approach for heavy metals source apportionment in this particular peri-urban area with a clear potential for future application in other regions.