A facile synthesis of Ag3PO4/BiPO4 p-n heterostructured composite as a highly efficient photocatalyst for fluoroquinolones degradation.

Ag3PO4/BiPO4 heterojunction photocatalysts with an intergrowth structure composed of sphere-shaped Ag3PO4 and nanorod BiPO4 were synthesized via a facile combination of solvothermal method and in-situ deposition process. They exhibit enhanced photocatalytic activities under sunlight irradiation, and the heterojunction composite with the 10 wt% loading amounts of Ag3PO4 presented the highest photocatalytic activities against norfloxacin (NFX), ofloxacin (OFXL) and ciprofloxacin (CIP), with high degradation efficiencies of 94.7%, 95.4% and 92.1%, respectively. Additionally, the Ag3PO4/BiPO4 photocatalyst demonstrates outstanding structural and photocatalytic stability. The superior performance was attributed to the effective charge transfer across the p-n heterojunction interface and the enhancement of light absorption. This work provides a new insight into the development of novel BiPO4-based heterojunction composites and meets the remediation for contaminated aqueous environment.

Metagenomics reveals functional profiling of microbial communities in OCP contaminated sites with rapeseed oil and tartaric acid biostimulation.

Organochlorine pesticides (OCPs) contaminated sites pose great threats to both human health and environmental safety. Targeted bioremediation in these regions largely depends on microbial diversity and activity. This study applied metagenomics to characterize the microbial communities and functional groups composition features during independent or simultaneous rapeseed oil and tartaric acid applications, as well as the degradation kinetics of OCPs. Results showed that: the degradation rates of α-chlordane, ß-chlordane and mirex were better when (0.50% w/w) rapeseed oil and (0.05 mol L-1) tartaric acid were applied simultaneously than singular use, yielding removal rates of 56.4%, 53.9%, and 49.4%, respectively. Meanwhile, bio-stimulation facilitated microbial enzyme (catalase/superoxide dismutase/peroxidase) activity in soils significantly, promoting the growth of dominant bacterial communities. Classification at phylum level showed that the relative abundance of Proteobacteria was significantly increased (p < 0.05). Network analysis showed that bio-stimulation substantially increased the dominant bacterial community's proportion, especially Proteobacteria. The functional gene results illustrated that bio-stimulation facilitated total relative abundance of degradation genes, phosphorus, carbon, nitrogen, sulfur metabolic genes, and iron transporting genes (p < 0.05). In metabolic pathways, functional genes related to methanogenesis and ammonia generation were markedly upregulated, indicating that bio-stimulation promoted the transformation of metabolic genes, such as carbon and nitrogen. This research is conducive to exploring the microbiological response mechanisms of bio-stimulation in indigenous flora, which may provide technical support for assessing the microbial ecological remediation outcomes of bio-stimulation in OCP contaminated sites.

Efficient Degradation of 2,4-Dichlorophenol on Activation of Peroxymonosulfate Mediated by MnO2.

Sulfate radical based-advanced oxidation process has received increasing interest in the remediation of wastewater and contaminated soil. In this study, degradation of 2, 4-dichlorophenol (2, 4-DCP) was investigated over peroxymonosulfate (PMS) activation by MnO2, which was prepared by liquid-phase oxidation method. The prepared MnO2 was characterized by transition electron microscopy, X-ray diffraction, N2 adsorption-desorption, and X-ray photoelectron spectroscopy. Characterization results showed that α-MnO2 exhibited the highest surface area and Mn (III) content. The PMS activation by MnO2 in 2, 4-DCP degradation followed the order of α-MnO2 > γ-MnO2 > ß-MnO2, which is dependent on the properties of MnO2 including crystal structure, surface area and Mn (III) content. Influences of initial concentration of 2, 4-DCP, PMS and MnO2 dosage, pH and co-existing inorganic ions on the degradation were examined. Electron paramagnetic resonance (EPR) and quenching experiments with ethanol and tert-butanol suggested that sulfate radicals were the dominant radicals in the process. Findings in this study indicated that α-MnO2 was an attractive catalyst for activation of PMS to degrade 2, 4-DCP in aqueous solution.

Feasibility of lettuce cultivation in sophoroliplid-enhanced washed soil originally polluted with Cd, antibiotics, and antibiotic-resistant genes.

Vegetable cultivation in soils polluted with heavy metals, antibiotics and a high abundance of antibiotic-resistance genes (ARGs) can seriously threaten human health through the food chain. Therefore, novel techniques that not only remediate soil, but also ensure food security are urgently required. In the present study, two successive washings with 20gL(-1) of sophoroliplid solution plus ultrasonication (35kHz) were effective in extracting 71.2% Cd, 88.2% tetracycline, 96.6% sulfadiazine, and 100% roxithromycin. Simultaneously, relative abundance of ARGs (tetM, tetX, sulI, and sulII) was decreased to 10(-7)-10(-8) (ARG copies/16S copies). Further, lettuce cultivation in the 2nd washed soil showed significant improvement in vegetable growth indices (fresh/dry weight, root surface area, chlorophyll content and soluble protein content) and a decrease in isolate counts for antibiotic-resistant bacterial endophytes and ARG abundance in lettuce tissues. This combined cleanup strategy provides an environmentally friendly technology for ensuring vegetable security in washed soils.

Persulfate activation with biochar supported nanoscale zero- valent iron: Engineering application for effective degradation of NCB in soil.

Nitrochlorobenzene (NCB) is very common in pesticide and chemical industries, which has become a major problem in soil environment. However, the remediation of NCB contaminated soil is received finite concern. Using biochar as a substrate for nanoscale-zero valent iron (nZVI/p-BC) to activate peroxodisulfate (PDS), a novel heterogeneous oxidative system had been applied in the current study to remediate NCB contaminants in soil. The degradation efficiencies and kinetics of m-NCB, p-NCB, and o-NCB by various systems were contrasted in soil slurry. Key factors including the dosage of nZVI/p-BC, the molar ratio of nZVI/PDS, initial pH and temperature on degradation of NCB were further examined. The results confirmed that the nZVI/p-BC/PDS displayed the remarkable performance for removing NCB compared with other systems. Higher temperature with nZVI/PDS molar ratio of 2:1 under the acidic condition favored the reduction of NCB. The treatment for NCB with optimal conditions were evaluated for the engineering application. The mechanism of nZVI/p-BC/PDS indicated that electron transfer between p-BC and nZVI was responsible for activation of PDS, generating active species (SO4•-, •OH and 1O2) via both the free and non-free radical pathways. Experimental results revealed prominent availability of nZVI/p-BC/PDS system in remediation of actual contaminated field by NCB.

Analysis of the Degradation of OCPs Contaminated Soil by the BC/nZVI Combined with Indigenous Microorganisms.

Organochlorine pesticides (OCPs) were typical persistent organic pollutants that posed great hazards and high risks in soil. In this study, a peanut shell biochar-loaded nano zero-valent iron (BC/nZVI) material was prepared in combination with soil indigenous microorganisms to enhance the degradation of α-hexachlorocyclohexane(α-HCH) and γ-hexachlorocyclohexane(γ-HCH) in water and soil. The effects of BC/nZVI on indigenous microorganisms in soil were investigated based on the changes in redox potential and dehydrogenase activity in the soil. The results showed as follows: (1) The specific surface area of peanut shell biochar loaded with nano-zero-valent iron was large, and the nano-zero-valent iron particles were evenly distributed on the peanut shell biochar; (2) peanut shell BC/nZVI had a good degradation effect on α-HCH and γ-HCH in water, with degradation rates of 64.18% for α-HCH and 91.87% for γ-HCH in 24 h; (3) peanut shell BC/nZVI also had a good degradation effect on α-HCH and γ-HCH in soil, and the degradation rates of α-HCH and γ-HCH in the 1% BC/nZVI reached 55.2% and 85.4%, second only to 1% zero-valent iron. The degradation rate was the fastest from 0 to 7 days, while the soil oxidation-reduction potential (ORP) increased sharply. (4) The addition of BC/nZVI to the soil resulted in a significant increase in dehydrogenase activity, which further promoted the degradation of HCHs; the amount of HCHs degradation was significantly negatively correlated with dehydrogenase activity. This study provides a remediation strategy for HCH-contaminated sites, reducing the human health risk of HCHs in the soil while helping to improve the soil and increase the activity of soil microorganisms.

Contaminant characterization at pesticide production sites in the Yangtze River Delta: Residue, distribution, and environmental risk.

The Yangtze River Delta (YRD) is the largest pesticide-producing region in the world. Contamination of pesticide production sites has always been a focus of public attention. Twenty pesticide production sites in YRD were selected to analyze the residue, distribution, and environmental risk of organic contaminants in soil and groundwater. A total of 194 organic chemicals were detected in all soil and groundwater samples from the 20 sites. Eighty-eight constituents of concern (COCs) exceeded the comparison values of Regional Screening Levels (RSLs), and 80 % exceeded the RSLs by more than five times. The toxic effects of COCs in soil and groundwater were dominated by the carcinogenic risk, referred as "non-threshold". Benzene toluene ethylbenzene & xylene (BTEX) and chloroaliphatic hydrocarbons (CAHs) were the most prevalent at pesticide sites in YRD rather than pesticides, followed by chlorobenzene, chlorophenols, and polycyclic aromatic hydrocarbons (PAHs). CAHs and BTEX could penetrate up to 24 m, while the others were primarily limited to 12 m. Most pesticide production sites showed a great contamination depth of >8 m, some even deeper than 20 m, posing a great risk of contamination to the confined aquifer. Due to the close interconnection of soil with water bodies, the shallow groundwater and adjacent surface water resources are also susceptible to suffering from environmental risk. More than half of the pesticide production sites in the YRD consist primarily of low-permeable clay layers, making in-situ contamination remediation difficult. This study provides a basis for developing remediation technology for pesticide sites in YRD and an ecological reference for further cleaning production and green manufacturing in the pesticide industry.

Rapid Degradation of Nitrochlorobenzene by Activated Persulfate Oxidation With Biochar Supported Nanoscaled Zero Valent Iron.

Although pesticide intermediates are a kind of typical toxic pollutant in contaminated sites, the remediation of these contaminants in groundwater and soils is of limited concern. In the present study we investigated the performance of a novel heterogeneous oxidation system, biochar supported nanoscaled-zero valent iron (nZVI/BC) activated persulfate (PS), in the oxidative degradation of nitrochlorobenzene (NCB), a typical pesticide intermediate. Peanut shell based nZVI/BC was prepared and used as the PS activator. The degradation kinetics of m-, p-, and o-NCB isomers in the aqueous phase were investigated. The effects of BC/nZVI composition (Fe/BC mass ratio), the amount of BC/nZVI and PS, and initial contaminant concentration on NCB removal were also examined. Results suggest that over 90% removals of three NCB isomers could be obtained by the nZVI/BC activated PS system at initial NCB concentration of 10 mg L-1. The combination of nZVI/BC composite and PS showed superior performance to PS alone. The optimal treatment condition was supposed as the Fe: BC ratio of 1:1, Fe amount of 6 mmol L-1, and the mole ratio of Fe to perfulfate of 1:1.

[Heavy Metal Contamination and Health Risk Assessment of Corn Grains from a Pb-Zn Mining Area].

A total of 92 corn grain samples, around the Pb-Zn mining area in Southwest China, were collected to evaluate the contamination and health risk of heavy metals. Heavy metals including Pb, Zn, Cd, Cr, and Ni in samples were analyzed. A single factor pollution index and comprehensive pollution index were calculated to assess the quality of corn grains. The potential health risks to adults and children due to the intake of these heavy metals through consumption of crops were evaluated using the health risk index. The results showed that the average contents of Pb, Zn, Cd, Cr, and Ni in corn grains were 0.30, 23.75, 0.21, 1.33, and 1.15 mg ·kg-1, respectively, Among the metals, the content of Zn, Pb, Cd, Cr, and Ni exceeded the national food hygiene standards. The Nemero index of Pb, Cd, Cr, and Ni ranged from 4.32 to 9.07, indicating an extremely high level, whereas the contamination of Zn reached an alarming level. The assessment results of the comprehensive health risk index for the corn grains indicated that the contamination of heavy metals poses health risks to adults and children by food ingestion; moreover, the children were more sensitive to various heavy metals than the adults. Principle component analysis revealed that the first main component dominated the sources of Pb, Cd, Cr, and Ni, while the second main component, Zn, might have originated from sources different from the other heavy metals. Positive correlations were not observed between the heavy metals in corns and soils.

Insights into removal of tetracycline by persulfate activation with peanut shell biochar coupled with amorphous Cu-doped FeOOH composite in aqueous solution.

Peanut shell biochar (BC) supported on Cu-doped FeOOH composite (Cu-FeOOH/BC) was synthesized using a facile and scalable method. The Cu-FeOOH/BC samples were characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS), x-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) techniques. Novel catalytic composites with different Cu/Fe molar ratios were compared systematically by activating persulfate (PS) for the tetracycline (TC) degradation. 0.5Cu-1FeOOH/BC (Cu/Fe molar ratio = 0.5:1) was confirmed as the optimum activation material and the removal of TC reached 98.0% after 120 min by combining with 20 mM PS at pH 7.0 and 25 °C. The influencing factors including catalyst loading, PS dosage, water matrix species, and pH on the performance system of 0.5Cu-1FeOOH/BC-PS were investigated, respectively. Reaction rate constants (Kobs) on catalyst dosages (0.05, 0.10, 0.20, and 0.30 g L-1) were 0.0072, 0.0101, 0.0244, and 0.0144 min-1, and 0.0090, 0.0146, 0.0244, and 0.0178 min-1 for the change of PS concentrations (5, 10, 20, and 30 mM), which indicated that increasing the concentrations of catalyst and PS appropriately improved TC degradation, but excessive dosages inhibited the reaction process of TC removal. The TC removal rate was inhibited by inorganic anions with the following order of HCO3- > Cl- > HPO42- > SO42- > NO3-. Free radical quenching and capture experiments under different pH values revealed that sulfate radicals existed predominantly in acidic conditions and hydroxyl radicals in alkaline conditions. The catalyst showed an excellent recyclability and stability and the removal efficiency of TC still remained over 90% after five consecutive uses. To conclude, coupling of 0.5Cu-1FeOOH/BC and PS can be successfully applied as an effective and stable technique for the treatment of refractory organic pollutants in wastewater.

Comparing polyvalent bacteriophage and bacteriophage cocktails for controlling antibiotic-resistant bacteria in soil-plant system.

Antibiotic resistant pathogenic bacteria (ARPB) residual in soil-plant system has caused serious threat against public health and environmental safety. Being capable of targeted lysing host bacteria, phage therapy has been proposed as promising method to control the ARPB contamination in environments. In this study, microcosm trials were performed to investigate the impact of various phage treatments on the dissipation of tetracycline resistant Escherichia coli K-12 and chloramphenicol resistant Pseudomonas aeruginosa PAO1 in soil-carrot system. After 70 days of incubation, all the four phage treatments significantly decreased the abundance of the pathogenic bacteria and the corresponding antibiotic resistance genes (tetW and cmlA) in the soil-carrot system (p < 0.05), following the order of the cocktail phage treatment (phages ΦYSZ1 + ΦYSZ2) > the polyvalent phage (ΦYSZ3 phage with broad host range) treatment > host-specific phage (ΦYSZ2 and ΦYSZ1) treatments > the control. In addition, the polyvalent phage treatment also exerted positive impact on the diversity and stability of the bacterial community in the system, suggesting that this is an environmentally friendly technique with broad applications in the biocontrol of ARPB/ARGs in soil-plant system.

Electromigration of cadmium in contaminated soils driven by single and multiple primary cells.

This study tentatively used an iron (Fe) and carbon (C) primary cell, instead of dc electric power, to drive the electromigration of cadmium in contaminated soils. The addition of acid to C compartment increased the electric potential, while the addition of acid to Fe compartment had a slight influence on the potential. It was feasible using the primary cell to drive the electromigration of cadmium in kaolin. The electromigration efficiencies were highly related to the soil pH. Lower pH led to greater migration efficiency. The mechanisms involved the desorption of cadmium from soils to pore solution and the electromigration of cadmium in the pore solution. The desorption was critical to the electromigration process. The series of primary cells could expand the treatment area, but the electromigration efficiencies of cadmium in each cell were less than that achieved by single primary cell. Since the potential gradient produced by the primary cell was rather low, the electromigration rate of pollutants was very low and remediation duration was long. The application would be acceptable in some specific sites, such as acidic soils or artificially controlled acid conditions so that heavy metals have been desorbed from soils.

'Agricultural Waste to Treasure' - Biochar and eggshell to impede soil antibiotics/antibiotic resistant bacteria (genes) from accumulating in Solanum tuberosum L.

Soil contamination with antibiotics and antibiotic resistant bacteria/genes (ARB/ARGs) has becoming an emerging environmental problem. Moreover, the mixed pollutants' transfer and accumulation from soil to tuberous vegetables has posed a great threat against food security and human health. In this work, the application of two absorbing materials (maize biochar and sulfate modified eggshell) was able to reduce the poisonous effect of soil antibiotics on potato root system by stimulate the dissipation of water-soluble antibiotics in soil; and also improve food quality by increasing potato starch, protein, fat, and vitamins. Meanwhile, both amendments could effectively decrease the classes and the accumulative abundance of ARB and ARGs (sulI, sulII, catI, catII, ermA, ermB) in the edible parts of potato. The lowest abundance of ARGs was detected in the biochar application treatment, with the accumulative ARG level of 8.9 × 102 and 7.2 × 102 copies mL-1 in potato peel (sull + catI + ermA) and tuberous root (sulI), respectively. It is the first study to demonstrate the feasibility of biochar and eggshell derived from agricultural wastes as green absorbing materials to reduce soil antibiotic, ARB, and ARGs accumulation risk in tuberous vegetable.

[Principal Component Analysis and Ecological Risk Assessment of Heavy Metals in Farmland Soils around a Pb-Zn Mine in Southwestern China].

The farmland soil around a Pb-Zn mine in southwestern China was studied. One hundred forty-nine surface soil samples were taken from 0-20 cm depth, and the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were tested. The correlations among these heavy metals were studied with multivariate analysis, and the potential sources of the metals were identified. The environmental risk of the metals was evaluated with the Potential Ecological Risk Index method. The results showed that the amounts of Cd, Pb, and Zn were at relatively high level, with average concentrations of 15.56, 419.4, and 933.4mg·kg-1 respectively, indicating the soil was heavily polluted. The average concentrations of Hg and As were 0.13 and 37.3mg·kg-1, suggesting moderate soil pollution. The average concentrations of Cu, Ni, and Cr were lower than Yunnan soil background values. The multivariate analysis suggested that the sources of Cd, Pb, Zn, Hg, and As were similar and came mainly from smelting activities in the mining area. The sources of Cu, Ni, and Cr were similar and can be attributed to natural sources. The comprehensive potential ecological risk index was 2294.8, which suggested a high potential ecological risk. In general, the farmland soils in the research area were polluted seriously by the mining and industrial activities.

Targeted inactivation of antibiotic-resistant Escherichia coli and Pseudomonas aeruginosa in a soil-lettuce system by combined polyvalent bacteriophage and biochar treatment.

High abundances of antibiotic-resistant pathogenic bacteria (ARPB) and antibiotic resistance genes (ARGs) in agricultural soil-plant systems have become serious threats to human health and environmental safety. Therefore, it is crucial to develop targeted technology to control existing antibiotic resistance (AR) contamination and potential dissemination in soil-plant systems. In this work, polyvalent bacteriophage (phage) therapy and biochar amendment were applied separately and in combination to stimulate ARPB/ARG dissipation in a soil-lettuce system. With combined application of biochar and polyvalent phage, the abundance of Escherichia coli K-12 (tetR) and Pseudomonas aeruginosa PAO1 (ampR + fosR) and their corresponding ARGs (tetM, tetQ, tetW, ampC, and fosA) significantly decreased in the soil after 63 days' incubation (p < 0.05). Similar results for endophytic K-12 and PAO1, and ARGs, were also obtained in lettuce tissues following combined treatment. Additionally, high throughput sequencing revealed that biochar and polyvalent phage synergetically improved the structural diversity and functional stability of the indigenous bacterial communities in soil and the endophytic ones in lettuce. Hence, this work proposes a novel biotechnology that combines biochar amendment and polyvalent phage therapy to achieve targeted inactivation of ARPB, which stimulates ARG dissipation in soil-lettuce systems.

Enhanced desorption of hexachlorobenzene from kaolin by single and mixed surfactants.

This study investigated the enhanced desorption of hexachlorobenzene (HCB) from spiked kaolin by single and mixed surfactants. The sorption of surfactants on kaolin followed myristyl pyridinium bromide (MPB) > Tween 80 > sodium dodecyl benzene sulfonic (SDBS). The desorption of HCB by single surfactant increased linearly with the increase of the aqueous micelle concentrations. The potential to enhance HCB desorption was Tween 80 > SDBS > MPB. When the dual mixed surfactants of SDBS-Tween 80 (MPB-Tween 80) were present, the desorption of HCB was larger than that by single SDBS (MPB) and less than that by single Tween 80. The total adsorbed surfactants were kept almost constant in SDBS-Tween 80 but decreased with the increased fraction of Tween 80 above 0.5 in MPB-Tween 80. The presence of little MPB in Tween 80 highly reduced the sorption loss of Tween 80 but slightly decreased the desorption of HCB. Whereas in SDBS-MPB, the presence of little MPB in SDBS remarkably decreased the desorption of HCB and enhanced the loss of SDBS, while the addition of little SDBS in MPB significantly enhanced the desorption and reduced the loss of MPB.

Desorption of copper and cadmium from soils enhanced by organic acids.

The adsorption/desorption behavior of copper and cadmium on soils was investigated in this study. The adsorption isotherm of copper and cadmium conformed to Langmuir equation better than Freundlich equation. The effect of ionic strength, pH, and organic acid, including ethylenediamine tetraacetic disodium acid salt (EDTA), citric acid, oxalic acid and tartaric acid, on the desorption of copper and cadmium was studied. The desorption of copper and cadmium increased with the increase of ionic strength, while the desorption decreased with the rise of pH. The desorption of copper and cadmium enhanced by organic acids was influenced by pH. EDTA showed excellent enhancement on the desorption of both copper and cadmium; citric acid demonstrated great enhancement on the desorption of copper but negligible enhancement on the desorption of cadmium; oxalic acid enhanced the desorption of copper only at pH around 6.4 and enhanced the desorption of cadmium in the pH range from 6.4 to 10.7; tartaric acid slightly enhanced the desorption of copper but negligibly enhanced the desorption of cadmium. The desorption mechanism in the presence of organic acids were explained as the competition of complexation, adsorption and precipitation. The net effect determined the desorption efficiency. This study provided guidance for the selection of organic acids to enhance the electrokinetic (EK) remediation of copper and cadmium from contaminated soils.

Electrokinetic movement of multiple chlorobenzenes in contaminated soils in the presence of beta-cyclodextrin.

This study investigated the electrokinetic (EK) behavior of multiple chlorobenzenes, including 1,2,3,4-tetrachlorobenzene (TeCB), 1,2,4,5-tetrachlorobenzene (i-TeCB), and 1,2,3-trichlorobenzene (TCB) in contaminated clayed soils. The effect of beta-cyclodextrin (beta-CD) on the EK removal of the chlorobenzenes was studied. The largest removal was obtained when Na2CO3/NaHCO3 buffer was used as anodic purging solution without beta-CD. The removal efficiencies were related to the aqueous solubilities of chlorobenzenes. With the same cumulative electroosmotic flow, greater solubility led to higher removal efficiency. The addition of beta-CD inhibited the EK removal efficiency of all chlorobenzenes. The inhibition increased with the increase of beta-CD concentration. With the same beta-CD concentration, the inhibition increased with the rise of electric potential. It was found that the inclusion compounds between beta-CD and chlorobenzenzes were less soluble than chlorobenzenes. The formation of the less soluble inclusion compounds reduced the aqueous solubility of chlorobenzenes and led to the partial immobilization of the chlorobenzenes that desorbed from soil. It was feasible to use the EK technology to remove chlorobenzenes in contaminated soils using water as the anodic flushing solution. The addition of beta-CD was not recommended for the EK removal of chlorobenzenes.

Ecotoxicological bioassays of sediment leachates in a river bed flanked by decommissioned pesticide plants in Nantong City, East China.

Traditionally, the toxicity of river contaminants is analyzed chemically or physically through river bed sediments. The biotoxicity of polluted sediment leachates has not caught our attention. This study aims to overcome this deficiency through a battery of biotests which were conducted to monitor comprehensive toxicity of sediment leachates for the Yaogang River in East Jiangsu Province of China, which is in close proximity to former pesticide plants. The general physical and chemical parameters of major pollutants were analyzed from river bed sediments collected at five strategic locations. The ecotoxicity analyses undertaken include overall fish (adult zebrafish) acute toxicity, luminescent bacteria (Vibrio fischeri) bioassay, and zebrafish embryo toxicity assay. Compared with the control group, sediment leachates increased the lethality, inhibited the embryos hatching and induced development abnormalities of zebrafish embryos, and inhibited the luminescence of V. fischeri. The results show that sediment leachates may assume various toxic effects, depending on the test organism. This diverse toxicity to aquatic organisms reflects their different sensitivity to sediment leachates. It is found clearly that V. fischeri was the organism which was characterized by the highest sensitivity to the sediment leachates. The complicated toxicity of leachates was not caused by one single factor but by multiple pollutants together. This indicates the need of estimations of sediment leachate not only taking into account chemical detection but also of applying the biotests to the problem. Thus, multigroup bioassays are necessary to realistically evaluate river ecological risks imposed by leachates.

Dynamic interplay between microbial denitrification and antibiotic resistance under enhanced anoxic denitrification condition in soil.

Mixed contamination of nitrate and antibiotics/antibiotic-resistant genes (ARGs) is an emerging environmental risk to farmland soil. This is the first study to explore the role of excessive anthropogenic nitrate input in the anoxic dissipation of soil antibiotic/ARGs. During the initial 10 days of incubation, the presence of soil antibiotics significantly inhibited NO3- dissipation, N2O production rate, and denitrifying genes (DNGs) abundance in soil (p < 0.05). Between days 10 and 30, by contrast, enhanced denitrification clearly prompted the decline in antibiotic contents and ARG abundance. Significantly negative correlations were detected between DNGs and ARGs, suggesting that the higher the DNG activity, the more dramatic is the denitrification and the greater are the antibiotic dissipation and ARG abundance. This study provides crucial knowledge for understanding the mutual interaction between soil DNGs and ARGs in the enhanced anoxic denitrification condition.