Risk assessment and ecotoxicological effects of leachates extracted from industrial district soils of Nanjing, China.

With the intensification of industrial development and urbanization, soil pollution is increasingly prominent. Therefore, the potential adverse effects caused by industrial activities need to be investigated. In this study, nine soil samples were collected from the industrial district of Nanjing, China, and the heavy metal concentrations were analyzed. Ambient severity of health (ASI) and ambient severity of ecology (ASII) caused by heavy metals in soil extracts were also evaluated via the multi-media environmental goals (MEG). The environmental risk assessment model was used to assess the health risk of soil extracts. The toxicity of soil extracts was diagnosed for wheat and Vicia faba. The results indicate that the contents of heavy metals were significantly different among the nine soil samples and mass concentration of heavy metals were as followed: Pb > Mn > As > Zn > Cd. Except for CK and S9, the total health impact of all sampling sites were greater than 1. Also, the total ecological hazard degrees of the five heavy metals were all greater than 1, which showed that the soil extracts were harmful to human health and ecological environment. According to the risk characterization model, the carcinogen risk of soil extracts was 1 to 10 orders of magnitude higher than that of non-carcinogens. Drinking water intake was the most direct and primary exposure route. In addition, the ecotoxicological results indicated that with the increase of heavy metal concentration, the activity of amylase (AMS) decreased, while the activity of peroxide (POD) increased, indicating that the soil extracts were toxic to V. faba. The micronucleus rates of V. faba root tips in the sampling soils were significantly higher compared with the control group, reflecting the higher genotoxicity. Our study provides theoretical support for the evaluation of potential health and ecological risks in this industrial district.

Risk assessment and ecotoxicological diagnosis of soil from a chemical industry park in Nanjing, China.

Soil pollution due to the activities of industrial parks, is becoming an increasingly serious issue, particularly throughout China. Therefore, it is essential to explore the soil pollution characteristics and its ecotoxicological effects on model species, such as higher plant species, in typical industrial areas. In this study, concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) were examined in the soil collected from 10 sampling sites at a chemical industry park in Nanjing, China. The pollution index was used to assess the heavy metal pollution level of soils, while the hazard index (HI) and carcinogenic risk index (RI) were calculated to assess the human health risk of soil PAHs. In addition, wheat (Triticum aestivum L.) was used as the model species to evaluate the ecotoxicological effects of polluted soil in pot experiments. Results showed that the content of heavy metals and PAHs varied greatly in soil samples, among which the heavy metal pollution at S1, S2 and S3 was the most serious. The health risk assessment of PAHs indicated that non-carcinogenic and carcinogenic values for all soil samples were below the threshold levels. Statistical analysis of the correlation between contaminated soil and toxic effects in wheat found that the significance values of regression equations were all less than 0.05 for chlorophyll content, peroxidase (POD) and amylase (AMS) activity. This indicates that the chlorophyll content, POD and AMS activity in wheat leaves could be suitable biomarkers for evaluation of the combined toxicity of multiple pollutants. This study provides a reference for future research on the risk assessment of soil containing multiple pollutants from industrial chemical parks.

Intestinal damage, neurotoxicity and biochemical responses caused by tris (2-chloroethyl) phosphate and tricresyl phosphate on earthworm.

Organophosphate esters (OPEs) draw growing concern about characterizing the potential risk on environmental health due to its wide usage and distribution. Two typical types of organophosphate esters (OPEs): tris (2-chloroethyl) phosphate (TCEP) and tricresyl phosphate (TCP) were selected to evaluate toxicity of OPEs to the soil organism like earthworm (Eisenia fetida). Histopathological examination (H&E), oxidative stress, DNA damage and RT-qPCR was used to identify the effects and potential mechanism of their toxicity. Hameatoxylin and eosin (H&E) demonstrated that intestinal cells suffered serious damage, and the observed up-regulation of chitinase and cathepsin L in mRNA levels confirmed it. Both TCEP and TCP significantly increased the DNA damage when the concentrations exceeded 1 mg/kg (p < 0.01), and a dose-response relationship was observed. In addition, TCEP and TCP also changed the acetylcholinesterase (AChE) activity and expression of genes associated with neurotoxic effects in earthworms even under exposure to low OPEs concentration (0.1 mg/kg). Moreover, genes associated with nicotinic acetylcholine receptors (nAChR) and carrier protein further demonstrated that highest concentration of TCEP (10 mg/kg) may have an overloading impact on the cholinergic system of E. fetida. Integrated Biological Response index (IBRv2) showed that TCEP exerted stronger toxicity than TCP under the same concentrations. We deduced that the observed intestinal damage, oxidative stress and neurotoxic effect might be the primary mechanisms of TCEP and TCP toxicity. This study provides insight into the toxicological effects of OPEs on earthworm model, and may be useful for risk assessment of OPEs on soil ecosystems.

Acute toxicity of multi-walled carbon nanotubes, sodium pentachlorophenate, and their complex on earthworm Eisenia fetida.

Laboratory experiments were undertaken to relate biomarker responses to the toxicities of multi-walled carbon nanotubes (MWCNTs) and sodium pentachlorophenate (PCP-Na), both individually and combined. The acute toxicities of MWCNTs and PCP-Na on earthworm Eisenia fetida were studied through different exposure methods (filter paper contact test, immersion contact test, and artificial soil contact test). Enzyme activity and malondialdehyde (MDA) content in the earthworm E. fetida exposed to MWCNTs and PCP-Na in filter paper contact test, both individually and under combined exposure, were determined. After exposure, PCP-Na induced observable acute toxicity while the MWCNTs induced slight toxicity. Interestingly the earthworms exposed to the mixture of MWCNTs and PCP-Na demonstrated different expression of enzymatic biomarkers from those exposed to MWCNTs or PCP-Na alone. Our results indicated that the toxicity of PCP-Na on E. fetida may be alleviated by the appearance of MWCNTs for all exposure methods except for immersion contact test.

Health risk assessment of semi-volatile organic pollutants in Lhasa River China.

The semi-volatile organic compounds in Lhasa River were determined qualitatively and quantitatively by gas chromatography method with mass spectrometric detection. Total concentrations of 23 organic pollutants in samples from five sites ranged from 1.56 to 2.78 µg/L. The average concentrations for ΣPAEs, ΣPAHs and ΣBTEXs obtained in this study were 1.53, 0.33 and 0.51 µg/L, respectively. Moreover, the results of analysis of variable showed that there were significant differences (P < 0.05) among the sites for levels of ΣPAHs, ΣPAEs and ΣBTEXs. Cluster analysis was applied to detect spatial similarity for grouping of sites under the monitoring network. The results indicated that the five sites in this study could be divided into two significant groups, i.e. low and high pollutant groups. Health risk assessment was conducted by multimedia environmental goals (MEG), risk quotient (RQ) for each pollutant and hazard quotient (HQ) approach from USA ecological risk assessment (ERA) for screening stage. Calculated both total ambient severity and RQ were less than 1 and therefore minimal risk to human and ecological health. For analysis results of HQ, whether for the ingestion exposure or dermal adsorption pathway were all less than 1, the results also agreed with the RQ model and MEG model for evaluating the potential for adverse health effects due to exposure semi-volatile organic compounds from surface water. Therefore, SVOCs in Lhasa River posed little or no threat to the health of local consumers and ecological environment.

Potential health impact and genotoxicity analysis of drinking source water from Liuxihe Reservoir (P.R. China).

Water from the Liuxihe Reservoir (a source of drinking water for Guangzhou City, P. R. China) was analyzed for semi-volatile organic compounds (SVOCs) and the results were used for a potential health impact assessment and genotoxicity test with the microalgae Euglena gracilis. The SVOCs were tested using USEPA Method 525.2, and the health risk assessment was conducted at a screening level using the hazard quotient (HQ) approach. Alkaline single-cell gel electrophoresis (comet assay) was used to evaluate DNA damage and determine the genotoxicity of the source water. The concentrations of the SVOCs in Liuxihe Reservoir were very low and phthalic acid esters were the main SVOCs present. The mean HQ values of pollutants were all less than one, indicating no risk. However, the lifetime carcinogenic risks (LCRs) were found to be close to the threshold of 1.00E-5. The results show that the water in the Liuxihe Reservoir might pose a potential carcinogenic risk to local residents. The highly concentrated extracts of the water samples could induce DNA damage in the microalgal cells and a dose-effect relationship was identified. These results showed that Liuxihe Reservoir water, as a source of drinking water, could pose a potential LCR to local consumers.

Mouse organ coefficient and abnormal sperm rate analysis with exposure to tap water and source water in Nanjing reach of Yangtze River.

Organ coefficients (including kidney, testis, liver and spleen coefficient) and abnormal sperm rate were used in our study to reflect the exposure to the Yangzte River water. The concentrations of total dissolved metals and semi-volatile organic compounds in tap and source water were measured by ICP-OES and GC-MS, respectively. After mice were fed with purified water (CK), Nanjing tap water (NJT) and Nanjing source water (NJS) for 90 day, the individual and organs (including kidney, testis, liver and spleen) of each mouse were weighted. And abnormal sperm types (such as hook less, banana-like form, amorphous, folded and two tails) were determined by microscope. The results showed that significant differences of liver coefficient between experimental group (NJT, NJS) and control group (CK) were observed; furthermore liver coefficient is positive correlation with the concentrations of total dissolved metals. However, no significant differences of abnormal sperm rates between experimental group (NJT, NJS) and control group (CK) were noted. So liver coefficient might be more sensitive than other organ coefficients to reflect the exposure to tap water and source water, while abnormal sperm rate could not be used to reveal the exposure to them.

Heavy metals levels in fish from aquaculture farms and risk assessment in Lhasa, Tibetan Autonomous Region of China.

Fish is consumed as a common food by humans due to its nutritional and therapeutic benefits. However, they can accumulate toxic chemicals (such as heavy metals, persistent organic pollutants) from water and food chain. Very few studies have been investigated on heavy metal contents in fish from Tibetan Autonomous Region of China. In order to study heavy metals levels in fish from aquaculture farms and evaluate the risk that human consume fish in this area, we collected four types of aquaculture fish species (6 big-head carps, 5 grass carps, 5 carps and 5 tilapias) from fisheries around Lhasa city in this study. 9 heavy metals (Cr, As, Cd, Pb, Cu, Ba, Co, Mn and V) in different tissues of fish were determined by an inductively coupled plasma mass spectrometer. Cr, Ba, Co, Mn and V could easily accumulate in the gill, and Cu was detected in the hearts of all the fishes. Toxic metal (As, Cd and Pb) contents were higher in the liver than those in other tissues, heavy metal levels were the lowest in the muscle among all tissues. Most of heavy metal concentrations in the tilapia tissues were higher than those in other fish tissues, especially arsenic. Arsenic content in the tilapia samples was ~2-4 times higher than the maximum levels (MLs) of contaminants in the national standard, and other metals were all lower than the MLs. Compared the estimated daily intake of heavy metals through fish consumption with tolerable daily intakes recommended by FAO, the metals daily intake of As, Cd and Pb from fish consumption might not pose serious health risk to the local inhabitants. It is therefore necessary to determine the dose level for human, which is considered to be taken daily over a lifetime without adverse effects.

Microalga Euglena as a bioindicator for testing genotoxic potentials of organic pollutants in Taihu Lake, China.

The microalga Euglena was selected as a bioindicator for determining genotoxicity potencies of organic pollutants in Meiliang Bay of Taihu Lake, Jiangsu, China among seasons in 2008. Several methods, including the comet assay to determine breaks in DNA and quantification of antioxidant enzymes were applied to characterize genotoxic effects of organic extracts of water from Taihu Lake on the flagellated, microalga Euglena gracilis. Contents of photosynthetic pigments, including Chl a, Chl b and carotenoid pigments were inversely proportion to concentrations of organic extracts to which E. gracilis was exposed. Organic extracts of Taihu Lake water also affected activities of superoxide dismutase (SOD) and peroxidase (POD) of E. gracilis. There were no statistically significant differences in SOD activities among seasons except in June but significant differences in POD activities were observed among all seasons. The metrics of DNA fragmentation in the alkaline unwinding assay (Comet assay), olive tail moment (OTM) and tail moment (TM), used as measurement endpoints during the genotoxicity assay were both greater when E. gracilis was exposed to organic of water collected from Taihu Lake among four seasons. It is indicated that the comet assay was useful for determining effects of constituents of organic extracts of water on E. gracilis and this assay was effective as an early warning to organic pollutants.

Impact of iron precipitant on toxicity of arsenic in water: a combined in vivo and in vitro study.

Removing arsenic (As) from drinking water is widely dependent on iron (Fe)-based coagulation/flocculation techniques. However, little is known about the influence of Fe precipitant on As toxicity. In this present study, the influence of Fe on As toxicity was determined at systems biology level by in vitro and in vivo experiments. In vitro study based on HepG2 cell line found that Fe increased the As toxicity on cell viability and DNA damage, indicating the synergetic toxic effects. However, when the Fe and As were simultaneously exposed to mice by drinking water for 90 days, the results showed that Fe reduced the changes of hepatic transcriptomic profiles and serum and urine metabolic profiles caused by As exposure, showing the antagonistic toxic effects. The antagonistic effects might be because Fe reduced As bioavailability and accumulation, which was verified by As and Fe levels in feces and liver. The results of this study indicate that Fe precipitant can influence the As toxicity. The interactions between As and Fe and their bioavailability might play important roles in the As toxicity. When assessing the safety of As in drinking water, it is necessary to fully consider the combined effects of As and Fe.

Antimony (Sb) pollution control by coagulation and membrane filtration in water/wastewater treatment: A comprehensive review.

Antimony (Sb) pollution in the water environment caused by the large-scale mining of Sb ore and the wide use of Sb-containing products seriously endangers human health and poses a great threat to the ecological environment. Coagulation is one of the most cost-effective technologies for Sb pollution control in water/wastewater treatment and has been widely used. However, a comprehensive understanding of Sb pollution control by coagulation, from fundamental research to practical applications, is lacking. In this work, based on the current status of Sb pollution in the water environment, a critical review of the Sb removal performance and mechanism by coagulation and related combined processes was carried out. The influencing factors of Sb removal performance by coagulation are introduced in detail. The internal mechanisms and improvement strategies of Sb removal by oxidation/reduction-coagulation and coagulation-membrane filtration technologies are emphasized. Moreover, given the development of Sb-removing coagulants and the resource utilization of Sb-containing sludge, future perspectives of coagulation for Sb removal are discussed. As the first review in this field, this work will illuminate avenues of basic research and practical applications for Sb and Sb-like pollution control in water/wastewater treatment.

Advantages of Bimetallic Organic Frameworks in the Adsorption, Catalysis and Detection for Water Contaminants.

The binary metal organic framework (MOF) is composed of two heterometallic ions bonded to an organic ligand. Compared with monometallic MOFs, bimetallic MOFs have greatly improved in terms of structure, porosity, active site, adsorption, selectivity, and stability, which has attracted wide attention. At present, many effective strategies have been designed for the synthesis of bimetallic MOF-based nanomaterials with specific morphology, structure, and function. The results show that bimetallic MOF-based nanocomposites could achieve multiple synergistic effects, which will greatly improve their research in the fields of adsorption, catalysis, energy storage, sensing, and so on. In this review, the main preparation methods of bimetallic MOFs-based materials are summarized, with emphasis on their applications in adsorption, catalysis, and detection of target pollutants in water environments, and perspectives on the future development of bimetallic MOFs-based nanomaterials in the field of water are presented.

Health risk of semi-volatile organic pollutants in Wujin river inflow into Taihu Lake.

Semi-volatile organic compounds (SVOCs), including polycyclic aromatic hydrocarbons (PAHs), phthalates and pesticides in water of Wujin river inflow into Taihu Lake, were detected for assessment of risk to human health. SVOCs were tested with Method 525.2 established by the US Environmental Protection Agency (EPA) and health risk assessment (HRA) was conducted by the hazard quotient (HQ) approach from US HRA for screening stage. The results for the liquid-solid extraction of water sample measured by gas chromatography/mass spectrometry (GC/MS) showed that three of the tested twenty-three semi-volatile organic contaminants posed potential health risk and the concentrations of 2,4-dinitrotoluene, di-n-butyl phthalate, chrysene and benzo(a)anthracene was 0.736, 15.201, 0.307, and 0.334 µg/l, respectively. SVOCs in the Wujin river water might induce risk to environmental health of Taihu Lake as a source of drinking water.

Genotoxicity of crude extracts of cyanobacteria from Taihu Lake on carp (Cyprinus carpio).

Genotoxicity of crude cyanobacteria extracts (CBE) from blooms in Taihu Lake, China toward common carp (Cyprinus carpio) was measured. The primary extracellular product was determined by HPLC to be Microcystin-LR (MC-LR, L for leucine and R for arginine) with an average concentration of 2.4 × 10(2) µg MC g(-1) dry weight of cyanobacteria. Acute toxicity to carp, expressed as the 72-h LC(50,) was 53 mg, dw cyanobacteria L(-1). Genotoxicity, as determined by the micronucleus (MN) and comet assays were both dose- and time-depended. Deformities of cellular organelles in liver and gill were observed by use of transmission electron microscopy (TEM). The results showed that MC-LR from cyanobacteria from Taihu Lake could induce genotoxic response and tissue-level morphological changes in common carp.

Organic pollutants and ambient severity for the drinking water source of western Taihu Lake.

Measurement of the organic compounds found in western Taihu Lake and evaluation of the ambient severity (AS) of the water using multimedia environmental goals (MEG) was conducted. The comet assay and the antioxidant enzyme approach were used to test the potential toxicity of water samples on the microalgae Euglena gracilis. Total concentrations of 25 organic pollutants in samples from two sites were 6.700 and 14.655 µg/l, respectively, with a calculated total ambient severity (TAS) of less than 1 and therefore minimal risk to human and ecological health. Organic extracts from the samples at these two sites was found to induce dose-dependent DNA damage on microalgae cells. DNA damage together with changes in superoxide dismutase (SOD) and peroxidase (POD) activities indicated that the potential pollutant toxicity was far higher at one of the two sites than at the other site. The comet assay combined with the activities of antioxidant enzymes may be of value as a biomarker for presence of organic pollutants in drinking water sources.

Toxicity of cyanobacterial bloom extracts from Taihu Lake on mouse, Mus musculus.

The acute and sub-chronic toxicities of cyanobacterial extract from Taihu Lake (PR China) on mouse (Mus musculus) were investigated in this study via intraperitoneal (i.p.) injection. Increases in liver/body weight ratios and pathological changes in mouse liver showed adverse effects at the organ level. Images from transmission electron microscopy (TEM) indicated that abnormal membrane structure occurred and that the organelles were damaged severely in the cells of liver and testis. The high dose group received i.p. injection of 12 mg lyophilized algae cells/kg body weight. Malondialdehyde (MDA) levels increased significantly in the livers of this group, along with a significant decrease in catalase (CAT) activity. These results revealed the existence of obvious oxidative stress. Comet assay results also suggested a dose-dependent relationship between DNA damage in hepatocytes/testicular cells and the amount of bloom extract administered to the mice. There was a significant increase in DNA damage compared to the control group and the genotoxicity of the cyanobacterial bloom to testicular cells was higher than in hepatocytes.

Protective effects of eicosapentaenoic acid on genotoxicity and oxidative stress of cyclophosphamide in mice.

The aim of this article is to elucidate the mechanism by which eicosapentaenoic acid (EPA) acts against cyclophosphamide (CP)-induced effects. The prevalence of micronuclei, the extent of lipid peroxidation, and the status of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) in both liver and serum of mice were used as intermediate biomarkers of chemoprotection. Lipid peroxidation and associated compromised antioxidant defenses (CAT and GPX) in CP treated mice were observed in the liver, serum, and were accompanied by increased prevalence of micronuclei in bone marrow. The number of MN was significantly different (p < 0.01) between the groups treated with CP (group III, IV, V, VI) and the solvent control (group II) (3.2 ± 0.7‰). There was a dose-dependent reduction in formation CP induced micronuclei by treatment with 100, 200, or 300 mg EPA/kg BW mice. Activities of SOD, CAT, and extent of lipid peroxidation were statistically different in liver cells of mice exposed to EPA only with CP compared with the CP group (group III). The present findings imply that EPA may be a potential antigenotoxic, antioxidant and chemopreventive agent and could be used as an adjuvant in chemotherapeutic applications.

Robust nitrate removal and bioenergy generation with elucidating functional microorganisms under carbon constraint in a novel multianode tidal constructed wetland coupled with microbial fuel cell.

This study investigated synthetic wastewater treatment under low inflow C/N ratio and characterized NO3--N-transforming and electricity-producing bacteria in a multi-anode tidal constructed wetland-microbial fuel cell (TFCW-MFC). The optimal concurrent average removal rates of NH4+-N and NO3--N were 73% and 78%, respectively, under a flood/rest/flood time of 4 h/2h/4h in "tide" mode accompanied by one recirculation. The lowest NO3--N concentration among all anodes was observed when the electrode gap was 45 cm. Similarly, the 45 cm anode exhibited selective enrichment of Variovorax and Azoarcus. Correction analysis showed that the high relative abundance of Azoarcus was crucial in enhancing NO3--N removal, and the internal resistance significantly decreased as the relative abundance of Acidovorax increased. These results suggest that NO3--N removal and bioelectricity generation can be promoted in a TFCW-MFC with limited carbon by improving the culture conditions for specific genera.

Response Characteristics of Nitrifying Bacteria and Archaea Community Involved in Nitrogen Removal and Bioelectricity Generation in Integrated Tidal Flow Constructed Wetland-Microbial Fuel Cell.

This study explores nitrogen removal performance, bioelectricity generation, and the response of microbial community in two novel tidal flow constructed wetland-microbial fuel cells (TFCW-MFCs) when treating synthetic wastewater under two different chemical oxygen demand/total nitrogen (COD/TN, or simplified as C/N) ratios (10:1 and 5:1). The results showed that they achieved high and stable COD, NH4 +-N, and TN removal efficiencies. Besides, TN removal rate of TFCW-MFC was increased by 5-10% compared with that of traditional CW-MFC. Molecular biological analysis revealed that during the stabilization period, a low C/N ratio remarkably promoted diversities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in the cathode layer, whereas a high one enhanced the richness of nitrite-oxidizing bacteria (NOB) in each medium; the dominant genera in AOA, AOB, and NOB were Candidatus Nitrosotenuis, Nitrosomonas, and Nitrobacter. Moreover, a high C/N ratio facilitated the growth of Nitrosomonas, while it inhibited the growth of Candidatus Nitrosotenuis. The distribution of microbial community structures in NOB was separated by space rather than time or C/N ratio, except for Nitrobacter. This is caused by the differences of pH, dissolved oxygen (DO), and nitrogen concentration. The response of microbial community characteristics to nitrogen transformations and bioelectricity generation demonstrated that TN concentration is significantly negatively correlated with AOA-shannon, AOA-chao, 16S rRNA V4-V5-shannon, and 16S rRNA V4-V5-chao, particularly due to the crucial functions of Nitrosopumilus, Planctomyces, and Aquicella. Additionally, voltage output was primarily influenced by microorganisms in the genera of Nitrosopumilus, Nitrosospira, Altererythrobacter, Gemmata, and Aquicella. This study not only presents an applicable tool to treat high nitrogen-containing wastewater, but also provides a theoretical basis for the use of TFCW-MFC and the regulation of microbial community in nitrogen removal and electricity production.

Spatiotemporal distribution and interaction of denitrifying functional genes in a novel DAS-NUA biofilter used for groundwater nitrate treatment.

A newly combined dewatered alum sludge (DAS) and neutralized used acid (NUA) biofilter has been constructed and investigated recently, aiming for improving nitrate (NO3--N) removal in simulated groundwater and exploring the spatiotemporal distribution of nirS and nosZ. The biofilter achieved 81.54% and 13.6 g N/ (m3 d) removal efficiency of NO3--N during the stabilization period. Spatiotemporal distributions of diversity and composition of nirS and nosZ varied approximately in two media with depths and time. Both DAS and NUA played important roles in attenuating nitrate because of predominant denitrifying genera functions, and the core differences were Rhodanobacter and Rhodobacter in DAS while Halomonas, Pseudogulbenkiania, and Cupriavidus in NUA. Acting as the strongly correlated genera, Magnetospirillum and Halomonas had a significantly positive or negative correlation with other dominant genera. Positive correlations existed among COD, TN, NO3--N, NO2--N, and both nirS and nosZ in the DAS filter, whereas the correlations were negative in the NUA filter. Particularly, the effluent concentration of NO3--N had a significantly negative correlation with the relative abundance of Rubrivivax and Pseudomonas. These results could be useful in adjusting the denitrification of nitrogen contaminants at the genetic level, especially in mitigating the influence of discharge of NO3--N on the process of groundwater restoration.