In Situ Toxicity Reduction and Food Safety Assessment of Pak Choi (Brassica campestris L.) in Cadmium-Contaminated Soil by Jointly Using Alkaline Passivators and Organic Fertilizer.

An economical and effective method is still lacking for cadmium (Cd) toxicity reduction and food product safety improvement in soil-vegetable systems. Therefore, this study aimed to reduce the Cd toxicity to pak choi (Brassica campestris L.) by jointly using passivators and organic fertilizer, highlighting food products' safety based on pot experiments. The results showed that compared with the control, organic fertilizer decreased the Cd content in edible parts and the soil's available Cd by 48.4% and 20.9% on average, respectively, due to the 0.15-unit increases in soil pH. Once jointly applied with passivators, the decrements increased by 52.3-72.6% and 32.5-52.6% for the Cd content in edible parts and for the soil's available Cd, respectively, while the pH increment increased by 0.15-0.46 units. Compared with the control, the transport factor of Cd was reduced by 61.9% and 50.9-55.0% when applying organic fertilizer alone and together with the passivators, respectively. The combination treatment of biochar and organic fertilizer performed the best in decreasing the Cd content in the edible parts and the soil's available Cd. The combination treatment of fish bone meal and organic fertilizer induced the greatest increases in soil pH. The grey relational analysis results showed that the combination treatment of biochar and organic fertilizer performed the best in reducing the potential Cd pollution risk, thereby highlighting the vegetable food safety. This study provides a potential economical and effective technology for toxicity reduction and food safety in Cd-polluted soil.

Typical Sulfonamide Antibiotics Removal by Biochar-Amended River Coarse Sand during Groundwater Recharge.

The high porosity of medium-coarse sand (MCS) layers in groundwater recharge areas presents a high environmental risk. Sulfamethoxazole (SMX) and trimethoprim (TMP) are two common sulfonamide antibiotics in surface water that have a high propensity to migrate into groundwater. In this study, four biochars were prepared and biochar-amended soil aquifer treatment (SAT) columns were constructed to remove SMX and TMP. Batch experiments demonstrated that the sorption isotherms conformed to the Freundlich model. The maximum adsorptions of biochars prepared at 700 °C were 54.73 and 67.62 mg/g for SMX and 59.3 and 73.38 mg/g for TMP. Electrostatic interaction may be one of the primary mechanisms of adsorption. The column experiments showed that the SMX and TMP removal rate of the biochar-amended SAT was as high as 96%, while that of the MCS SAT was less than 5%. The addition of biochar greatly improved the retention capacity of the pollutants in the MCS layer in the groundwater recharge area and effectively reduced environmental risk.

Quantify the effects of groundwater level recovery on groundwater nitrate dynamics through a quasi-3D integrated model for the vadose zone-groundwater coupled system.

Groundwater level (GWL) recovery in some semiarid regions, attributed to mitigation countermeasures for groundwater depletion, potentially causes nitrate accumulated in the vadose zone to be introduced into the aquifer. However, the extent to which GWL recovery affects interactions between the vadose zone and saturated aquifers, migration pathways of soil nitrogen and groundwater nitrate dynamics have not been explicitly determined. This study established a quasi-3D feedback model for the vadose zone-groundwater coupled system in a typical GWL recovery area and quantitatively evaluated the effects of GWL recovery on nitrate-N leaching fluxes via the vadose zone and groundwater nitrate-N dynamics. Within the framework of the integrated model, both the water/contaminant leaching fluxes and the depth to groundwater were exchanged at each flow time step. The obtained results reveal that the temporal changes in nitrate-N leaching fluxes depended on the behaviors of precipitation, farmland irrigation and lithology of the vadose zone, while its spatial patterns were determined by both the GWL undulation and the vertical profiles of nitrate-N content. Furthermore, the GWL recovery caused the magnitude of the nitrate-N leaching fluxes into the aquifer to increase by 44.4%. Along with the GWL recovery, the phreatic aquifer volume increased by 7.47%, and the nitrate-N mass herein increased by 40.06%, which was largely driven by the nitrate-N leaching flux. Consequently, the average groundwater nitrate-N concentration in the GWL recovery region increased by approximately 2.4 mg/L, apart from the artificial recharge route. This finding suggests that the intensified leaching of soil contaminants, given the circumstances of GWL recovery, has a negative effect on groundwater quality. An appropriate groundwater management scheme is therefore urgently required to achieve an optimal balance between GWL recovery and groundwater environment.

Efficient electrocatalytic nitrate reduction via boosting oxygen vacancies of TiO2 nanotube array by highly dispersed trace Cu doping.

Nitrate pollution of water bodies is a serious global-scale environmental problem. The electrocatalytic nitrate reduction reaction (NO3RR) using Cu-based electrodes allows excellent nitrate removal; however, its long-term operation results in copper leaching, leading to health risks. This study proposes a strategy for efficient nitrate removal through the activation of oxygen vacancies on a highly dispersed Cu-doped TiO2 nanotube array (Cu/TNTA) cathode via electrodeposition. The mechanism underlying the activation of oxygen vacancies and enhancement in charge transfer at the cathode-pollutant interface upon trace (0.02 wt%) Cu doping is elucidated by electron paramagnetic resonance analysis, UV-visible diffuse reflection spectroscopy, and Raman spectroscopy. The Cu/TNTA-300 exhibits a nitrate removal rate of 84.3% at 12 h; the electrode activity did not decrease after 10 cycles, and no Cu2+ was detected in the solution. Electrochemical characterization and density functional theory calculations demonstrate that Cu doping promotes efficient charge transfer between nitrate and the electrode and reduces the energy barrier of the nitrate reduction reaction. This work provides a platform for novel design of cathodes for use in efficient and safe electrocatalytic nitrate reduction in environmental water bodies.

In-situ growing of metal-organic frameworks on iron mesh as a recyclable remediation material for removing hexavalent chromium from groundwater.

The recovery and reuse of adsorbents is crucial for the effectiveness and sustainability of mitigation methods for groundwater pollution. Considering the difficulty in recovering powder materials and the low mechanical strength of membrane materials, we developed a sheet material with good recyclability and certain mechanical strength. In this study, an in situ synthesized MIL-100(Fe) film sample was produced by hydrothermal reaction using a commercially available iron mesh as the substrate. The MIL-100(Fe) samples were characterized by SEM, XRD, XPS, and FT-IR. The experiments showed that the material presented excellent removal ability toward Cr(VI) and good recovery performance. In the fourth cycle test, the Cr(VI) removal rate reached more than 95%. The material characterization and adsorption kinetics indicated that the removal mechanism was oxidation-reduction reaction and electrostatic adsorption. The removal experiments at different pH values and with different co-existing ions demonstrated that the material can maintain good removal capacity at pH values between 2 and 8, and common ions in groundwater can promote the removal of Cr(VI) under neutral conditions. The recycling test demonstrated that the sample can be reused. After the sample was recovered and calcined in an inert environment, a network sample containing zero-valent iron was obtained, and it removed Cr(VI) from water at a low pH in 20 min. This study provides a new alternative for the practical removal of Cr(VI) from groundwater.

[Analysis of the Urban Water Eco-environment Protection Strategy in the Beijing-Tianjin-Hebei Region from "Three Waters" Overall Planning].

Clarifying the direction and strategy of water eco-environment protection in the Beijing-Tianjin-Hebei region is of great significance for realizing the water eco-environment protection and high-quality, coordinated development of the Beijing-Tianjin-Hebei area, as well as the goal of building a beautiful China by 2035. From the perspective of "Three Waters" overall planning, based on the urban scale of the Beijing-Tianjin-Hebei region, this study constructed six dimensions of water resources, water environment, water ecology (Three Waters), socio-economic development level, pollutant emissions, and environmental governance efforts. The water eco-environment protection strategy analysis system provided a logical framework for quantifying the current status of the water eco-environment. The ideal value was compared in each city, the PROMETHEE method was used to quantify the gap between each city and the ideal value of water eco-environment protection, and the current situation of the water eco-environment in Beijing-Tianjin-Hebei cities was evaluated. Additionally, water eco-environment protection strategies were formulated according to local conditions. The ranking of the comprehensive level of water eco-environment protection from high to low was Beijing>Tianjin>Qinhuangdao>Hengshui>Zhangjiakou>Langfang>the mean value of net flow value (Phi)>Handan>Chengde>Cangzhou>Baoding>Tangshan>Shijiazhuang>Xingtai; a large gap remained between the level and the ideal value. The hierarchical analysis showed that the advantages and disadvantages of each city's water eco-environment protection were different from dimensions to indicators, and they had the characteristics of local water eco-environment protection. Future efforts should determine the water ecological, environmental protection indicator level of each city in the Beijing-Tianjin-Hebei region, conduct a separate analysis for each city, and propose protection strategies for future development, as well as continue to help the water eco-environmental protection in the Beijing-Tianjin-Hebei region.

A novel comprehensive risk assessment method for sudden water accidents in the Middle Route of the South-North Water Transfer Project (China).

The Middle Route of the South-North Water Transfer Project in China consists of a long open canal and complex hydraulic structures. It provides drinking water for Beijing, Shijiazhuang, and other cities under extremely strict water quality requirements. In the recent decades, water pollution accidents have frequently occurred in water transfer projects. Scientific and effective risk assessment is needed to assess the impact on the overall emergency management, which should be considered to incorporate social, economic, and environmental issues in the timely response to and management of emergencies. In this study, we combine the Drivers-Pressures-State-Impact-Response model, fuzzy comprehensive evaluation method, and coordinated development degree model into a comprehensive risk assessment tool. This new approach was tested on an emergency drilling simulation related to a sudden MRP water pollution accident in 2016. Based on the combined integration weight ranking, "water delivery status," "pollution accident characteristics," "town size," and "public satisfaction" play prominent roles in the risk assessment. Especially, "town size" is identified as the most important influent factor. The Drivers-Pressures-State-Impact-Response model index system and comprehensive risk assessment method can be used to evaluate accidents more scientifically and versatile, which helps managers or experts to make faster and more efficient decisions.

Quantifying effects of conservation practices on non-point source pollution in the Miyun Reservoir Watershed, China.

Non-point source (NPS) pollution, including fertilizer and manure application, sediment erosion, and haphazard discharge of wastewater, has led to a wide range of water pollution problems in the Miyun Reservoir, the most important drinking water source in Beijing. In this study, the Soil and Water Assessment Tool (SWAT) model was used to evaluate NPS pollution loads and the effectiveness of best management practices (BMPs) in the two subwatersheds within the Miyun Reservoir Watershed (MRW). Spatial distributions of soil types and land uses, and changes in precipitation and fertilizer application, were analysed to elucidate the distribution of pollution in this watershed from 1990 to 2010. The results demonstrated that the nutrient losses were significantly affected by soil properties and higher in both agricultural land and barren land. The temporal distribution of pollutant loads was consistent with that of precipitation. Soil erosion and nutrient losses would increase risks of water eutrophication and ecosystem degradation in the Miyun Reservoir. The well-calibrated SWAT model was used to assess the effects of several Best Management Practices (BMPs), including filter strips, grassed waterways, constructed wetlands, detention basins, converting farmland to forest, soil nutrient management, conservation tillage, contour farming, and strip cropping. The removal rates of those BMPs ranged from 1.03 to 38.40% and from 1.36 to 39.34% for total nitrogen (TN) and total phosphorus (TP) loads, respectively. The efficiency of BMPs was dependent on design parameters and local factors and varied in different sub-basins. This study revealed that no single BMP could achieve the water quality improvement targets and highlighted the importance of optimal configuration of BMP combinations at sub-basin scale. The findings presented here provide valuable information for developing the sustainable watershed management strategies.

A three chamber bioelectrochemical system appropriate for in-situ remediation of nitrate-contaminated groundwater and its reaction mechanisms.

A novel laboratory experiment of three chamber bioelectrochemical (surface water-sediment-groundwater, SSG) system was established in this study, which combined a sediment microbial fuel cell (SMFC) reactor and biofilm electrode reactor (BER) and was self-driven. Simulated groundwater was firstly used to explore the reaction mechanisms of this system. The simulated groundwater conditions were static and the surface water and the groundwater systems were isolated. The results showed that the SMFC continuously supplied a stable voltage of 622 mV ±â€¯20 mV, driving the BER and the related nitrate removal process. Compared to the control systems, the SSG system had higher nitrate removal with a denitrification rate of 3.87 mg N/(L·h). In addition, the sediment organic matter in the SMFC reactor decreased by 66.2%. Based on the electrochemical analysis and microbial community analysis, the SMFC reactor and BER worked synergistically to enhance the performance of both reactors in this system. The presence of microorganisms accelerated the electron transfer efficiency throughout the system, and the microcurrent helped a more fixed community structure to develop and stimulated the growth of denitrifying bacteria. The dominant genera detected in the mature biofilm samples were all microorganisms common in soil and groundwater, indicating that this system may be environmentally friendly. The nitrate removal efficiency for actual groundwater was higher than that for the simulated groundwater, indicating that the elements in the actual groundwater promote the nitrate removal efficiency. These results indicate that the SSG system has the potential for in-situ nitrate bioremediation, with minimal maintenance and health risk.

A Semi-distributed Model for Predicting Faecal Coliform in Urban Stormwater by Integrating SWMM and MOPUS.

The microbial contamination of urban stormwater has an important impact on human health and stormwater reuse. This study develops an exploratory semi-distributed model, MOPUS_S, which can simulate faecal coliform levels in separate sewer systems in urban catchments. The MOPUS_S was built by coupling the SWMM model and the microbial MOPUS model. The parameters associated with the deposition and wash-off of microorganisms were more influential than those related to microorganism survival processes. Compared to other existing bacterial models, MOPUS_S showed comparable performance in predicting faecal coliform concentrations. The performance varied largely between rainfall events, with Nash-Sutcliffe efficiency (NSE) values ranging from -5.03 to 0.39 and R² ranging from -0.02 to 0.83, respectively. The model simulation results for low and medium concentrations were better than those for the peak concentrations. Poor simulation results of peak concentrations obviously affect the overall model performance. In general, MOPUS_S could be capable of predicting the faecal coliform load in urban catchments and be a useful tool for urban stormwater management planning.

Factors affecting microbial and physico-chemical pollutants in stormwater in a typical Chinese urban catchment.

An understanding of microbial pollution characteristics is needed for stormwater reuse and development of microorganism simulations in urban stormwater. This study investigated the discharge characteristics of faecal indicator bacteria (faecal coliforms) in urban runoff by field sampling both the underlying surfaces and the stormwater pipe outlet. Faecal coliform contamination in urban runoff was found to be frequent, and the highest instantaneous concentration reached 2.42 × 106 MPN/100 ml. Faecal coliforms did not show a consistent first flush effect amongst the different surfaces sampled, and this was exacerbated under rainfall events with high intensity. PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluation) and GAIA (Geometrical Analysis for Interactive Aid) analyses were further applied to explore the ranking of pollutants, the relationship among the pollutants, and the factors affecting the contamination in cases of multiple underlying surfaces, multiple pollutants and rainfall events. For the pollutants of suspended solids (SS), total phosphorus (TP) and chemical oxygen demand (COD), the road sample contamination was significantly higher than on the roof surfaces. No such trend in ranking of faecal coliforms was observed. Rainfall depth and intensity were found to have a significant influence on stormwater contamination by physico-chemical pollutants, while having a somewhat smaller influence on faecal coliform contamination. Faecal coliform contamination is closely associated with the index related to the antecedent dry period. The average temperature and average relative humidity also showed a positive relationship with faecal coliform contamination. The effects of antecedent dry period duration on contamination of physico-chemical pollutants and faecal coliform are completely opposite. Antecedent dry period duration was positively related to the contamination of physico-chemical pollutants, but negatively related to faecal coliform contamination. Therefore, three variables, i.e., antecedent dry period duration, average temperature and average relative humidity, might be used to model the survival/die-off of faecal coliform during the antecedent dry period.

Effects of the spatial resolution of urban drainage data on nonpoint source pollution prediction.

Detailed urban drainage data are important for urban nonpoint source (NPS) pollution prediction. However, the difficulties in collecting complete pipeline data usually interfere with urban NPS pollution studies, especially in large-scale study areas. In this study, NPS pollution models were constructed for a typical urban catchment using the SWMM, based on five drainage datasets with different resolution levels. The influence of the data resolution on the simulation results was examined. The calibration and validation results of the higher-resolution (HR) model indicated a satisfactory model performance with relatively detailed drainage data. However, the performances of the parameter-regionalized lower-resolution (LR) models were still affected by the drainage data scale. This scale effect was due not only to the pipe routing process but also to changes in the effective impervious area, which could be limited by a scale threshold. The runoff flow and NPS pollution responded differently to changes in scale, primarily because of the difference between buildup and washoff and the more significant decrease in pollutant infiltration loss and the much greater increase of pollutant flooding loss while scaling up. Additionally, scale effects were also affected by the rainfall type. Sub-area routing between impervious and pervious areas could improve the LR model performances to an extent, and this approach is recommended to offset the influence of spatial resolution deterioration.

Microbial community dynamics in a pilot-scale MFC-AA/O system treating domestic sewage.

To investigate the effluent concentrations of pollutants, electricity production and microbial community structure, a pilot-scale microbial fuel cell coupled anaerobic-anoxic-oxic system for domestic sewage treatment was constructed, and continuously operated for more than 1 year under natural conditions. The results indicated that the treatment system ran well most of the whole period, but both effluent qualities and electricity production deteriorated at low temperature. The results of MiSeq sequencing showed that the microbial community structures of both anode and cathode biofilms changed extensively during long-term operation and were correlated with changes in effluent qualities. Fifteen genera of electricigens were detected in the anode biofilm, mainly including Clostridium, Paracoccus, Pseudomonas, and Arcobacter. Partial Mantel test results showed that the temperature had significant effects on the microbial community structure. The electricity production was found to have higher relevance to the variation of the anodic community than that of the cathodic community.