The Experts below are selected from a list of 43644 Experts worldwide ranked by ideXlab platform
Biswajeet Pradhan - One of the best experts on this subject based on the ideXlab platform.
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a novel machine learning based approach for the risk assessment of nitrate Groundwater Contamination
Science of The Total Environment, 2018Co-Authors: Farzaneh Sajedihosseini, Arash Malekian, Biswajeet Pradhan, Bahram Choubin, Omid Rahmati, Sabrina Cipullo, Frederic CoulonAbstract:This study aimed to develop a novel framework for risk assessment of nitrate Groundwater Contamination by integrating chemical and statistical analysis for an arid region. A standard method was applied for assessing the vulnerability of Groundwater to nitrate pollution in Lenjanat plain, Iran. Nitrate concentration were collected from 102 wells of the plain and used to provide pollution occurrence and probability maps. Three machine learning models including boosted regression trees (BRT), multivariate discriminant analysis (MDA), and support vector machine (SVM) were used for the probability of Groundwater pollution occurrence. Afterwards, an ensemble modeling approach was applied for production of the Groundwater pollution occurrence probability map. Validation of the models was carried out using area under the receiver operating characteristic curve method (AUC); values above 80% were selected to contribute in ensembling process. Results indicated that accuracy for the three models ranged from 0.81 to 0.87, therefore all models were considered for ensemble modeling process. The resultant Groundwater pollution risk (produced by vulnerability, pollution, and probability maps) indicated that the central regions of the plain have high and very high risk of nitrate pollution further confirmed by the exiting landuse map. The findings may provide very helpful information in decision making for Groundwater pollution risk management especially in semi-arid regions.
Erik Nixdorf - One of the best experts on this subject based on the ideXlab platform.
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development and application of a novel method for regional assessment of Groundwater Contamination risk in the songhua river basin
Science of The Total Environment, 2017Co-Authors: Erik Nixdorf, Yuanyuan Sun, Mao Lin, Olaf KolditzAbstract:The main objective of this study is to quantify the Groundwater Contamination risk of Songhua River Basin by applying a novel approach of integrating public datasets, web services and numerical modelling techniques. To our knowledge, this study is the first to establish Groundwater risk maps for the entire Songhua River Basin, one of the largest and most Contamination-endangered river basins in China. Index-based Groundwater risk maps were created with GIS tools at a spatial resolution of 30arc sec by combining the results of Groundwater vulnerability and hazard assessment. Groundwater vulnerability was evaluated using the DRASTIC index method based on public datasets at the highest available resolution in combination with numerical Groundwater modelling. As a novel approach to overcome data scarcity at large scales, a web mapping service based data query was applied to obtain an inventory for potential hazardous sites within the basin. The Groundwater risk assessment demonstrated that <1% of Songhua River Basin is at high or very high Contamination risk. These areas were mainly located in the vast plain areas with hotspots particularly in the Changchun metropolitan area. Moreover, Groundwater levels and pollution point sources were found to play a significantly larger impact in assessing these areas than originally assumed by the index scheme. Moderate Contamination risk was assigned to 27% of the aquifers, predominantly associated with less densely populated agricultural areas. However, the majority of aquifer area in the sparsely populated mountain ranges displayed low Groundwater Contamination risk. Sensitivity analysis demonstrated that this novel method is valid for regional assessments of Groundwater Contamination risk. Despite limitations in resolution and input data consistency, the obtained Groundwater Contamination risk maps will be beneficial for regional and local decision-making processes with regard to Groundwater protection measures, particularly if other data availability is limited.
Qingqing Shi - One of the best experts on this subject based on the ideXlab platform.
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a review of Groundwater Contamination near municipal solid waste landfill sites in china
Science of The Total Environment, 2016Co-Authors: Zhiyong Han, Guozhong Shi, Luoyu Wei, Qingqing ShiAbstract:Landfills are the most widely used method for municipal solid waste (MSW) disposal method in China. However, these facilities have caused serious Groundwater Contamination due to the leakage of leachate. This study, analyzed 32 scientific papers, a field survey and an environmental assessment report related to Groundwater Contamination caused by landfills in China. The Groundwater quality in the vicinity of landfills was assessed as "very bad" by a comprehensive score (FI) of 7.85 by the Grading Method in China. Variety of pollutants consisting of 96 Groundwater pollutants, 3 organic matter indicators, 2 visual pollutants and 6 aggregative pollutants had been detected in the various studies. Twenty-two kinds of pollutants were considered to be dominant. According to the Kruskal-Wallis test and the median test, Groundwater Contamination differed significantly between regions in China, but there were no significant differences between dry season and wet season measurements, except for some pollutants in a few landfill sites. Generally, the Groundwater Contamination appeared in the initial landfill stage after five years and peaked some years afterward. In this stage, the Nemerow Index (PI) of Groundwater increased exponentially as landfill age increased at some sites, but afterwards decreased exponentially with increasing age at others. After 25years, the Groundwater Contamination was very low at selected landfills. The PI values of landfills decreased exponentially as the pollutant migration distance increased. Therefore, the Groundwater Contamination mainly appeared within 1000m of a landfill and most of serious Groundwater Contamination occurred within 200m. The results not only indicate that the Groundwater Contamination near MSW landfills should be a concern, but also are valuable to remediate the Groundwater Contamination near MSW landfills and to prevent the MSW landfill from secondary pollutions, especially for developing countries considering the similar situation of MSW disposal.
Yuting Xiao - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the building pressure cycling method for evaluating vapor intrusion from Groundwater Contamination
Environmental Science and Pollution Research, 2020Co-Authors: Yanqiu Liu, Yuting Xiao, Jun Man, Yue Wang, Wei Tang, Qiang Chen, Yijun YaoAbstract:Vapor intrusion (VI) risk assessments determine the cleanup level of Groundwater in the absence of ingestion. In recent VI investigations, the building pressure cycling (BPC) method has been applied to help minimize ambiguity caused by temporal variability of indoor air samples that are important to risk assessments, and, consequently, determine Groundwater cleanup level accurately. In this study, we use a three-dimensional numerical model to examine the dynamic migration of VOCs from Groundwater after the application of BPC. First, we validated the numerical model with field measurements. Then, the verified model is used to investigate the effects of site-specific features in determining the performance of BPC operation. At last, we summarize past field applications of BPC to examine the simulated results. Our study indicates that the BPC-induced indoor depressurization can increase the building loading rate in the first 2–3 h, which would then drop to 2–3 times of that with natural conditions in most cases of Groundwater Contamination. In some cases involving a strong source, e.g., a vapor source above the capillary fringe or a Groundwater source with sandy soil above the Groundwater level, the normalized building loading rates can be maintained as high as 4–9 without decrease after the first 2–3 h. Significantly higher increase in building loading rate may indicate a potential presence of a preferential pathway between the Groundwater Contamination and concerned building.
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modeling capillary fringe effect on petroleum vapor intrusion from Groundwater Contamination
Water Research, 2019Co-Authors: Yuting XiaoAbstract:Abstract At contaminated sites, indoor inhalation of volatile organic compounds from Groundwater Contamination, known as vapor intrusion (VI), is an important exposure pathway to determine Groundwater cleanup level. Based on empirical analysis, US EPA concluded that there is a low probability for vapors from fuel hydrocarbons dissolved in Groundwater to induce indoor concentrations that exceed risk-based standards, and recommended 6 feet vertical building-source separation distance as the risk screening tool for such cases. In this study, we examine this recommendation by performing numerical modeling to investigate the detailed effects of the capillary fringe on petroleum vapor biodegradation and attenuation. First, the numerical model is validated by comparison with laboratory data and field measurements in US EPA's database. Then the verified model is used to simulate two scenarios involving the capillary fringe effect, one with a Groundwater source at various depth and the other with a soil gas source located above the Groundwater level. For a Groundwater contaminant source, the capillary fringe plays a significant role in VI by controlling the soil moisture content and oxygen availability, thus affecting the soil gas concentration biodegradation and attenuation. Specifically, the capillary fringe effect can significantly decrease the indoor air concentration by decreasing upward diffusion rates of hydrocarbon, increasing the thickness of the aerobic zone, and enhancing aerobic biodegradation. As a result, it is highly unlikely for sources located at Groundwater level to induce unacceptable vapor intrusion risks, supporting US EPA's recommendation. Moreover, the simulations suggest that the vertical smear zone of residual light non-aqueous liquid Contamination, induced by temporal fluctuations of Groundwater level, may lead to a potential threat to indoor air quality for a short vertical source-building separation distance, and thus requires more attention. The sensitivity test of the numerical model also indicates that it is the vertical separation distance between building foundation and the top of the smear zone instead of the smear zone thickness that should be given more attention during the investigation.
Dong Wang - One of the best experts on this subject based on the ideXlab platform.
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The Human Health Risk Assessment Based on Process Simulation and Uncertainty Analysis
Atlantis Press, 2018Co-Authors: Yue Pan, Xiankui Zeng, Xinyu Gao, Dong WangAbstract:Water resource is an important part of human living and production. With the modernization of cities, the problem of Groundwater Contamination is becoming more and more serious. It is outstanding to effectively assess the risk of Groundwater Contamination to human health. This paper proposes a human health risk assessment method based on the simulation of contaminant transport process and parameter uncertainty analysis. The method combines health risk assessment with Groundwater contaminant transport processes and applies the TOUGH2 program to simulate the temporal and spatial distribution of contaminant in Groundwater. In order to improve the accuracy of the assessment results, the influence of the uncertainty of the transport model on human health risk assessment is taken into account. And the key parameter (e.g., the permeability) of the transport model is inversed by Markov chain Monte Carlo simulation method. Based on a sandbox experiment, the human health risk exposed to a typical dense non-aqueous phase liquids contaminant tetrachloroethylene (PCE) is evaluated by considering the parameter uncertainty of the PCE transport model, which confirmed that the method can provide decision-making information for the management and prevention of contaminated sites
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emission distribution and leaching of methyl isothiocyanate and chloropicrin under different surface containments
Chemosphere, 2007Co-Authors: Y Zhang, Dong WangAbstract:Abstract The environmental fate of fumigants methyl isothiocyanate (MITC) and chloropicrin (CP) is of great concern for potential air and Groundwater Contamination while retaining sufficient concentrations for pest control efficacy. The emission, gas phase distribution, leaching, and persistence of MITC and CP were examined in repacked columns filled with sandy soils under three surface conditions: tarp without irrigation, tarp with limited irrigation, and 5-d irrigation without tarp cover. For MITC, cumulative emission constituted 62%, 36%, and 0.3% of the amount applied under tarp without irrigation, tarp with limited irrigation, and 5-d irrigation without tarp surface conditions, respectively. The corresponding cumulative emission losses were 45%, 30%, and 5.4% for CP. During the first 24 h after injection, soil air concentrations of the two fumigants were much higher in the 15–25 cm depth range than other depths in the soil profile. Small amounts of leaching occurred for both fumigants, indicating potential for Groundwater Contamination should heavy rain fall or irrigation occurs immediately after soil fumigation. Very small amounts of residual MITC and CP (
