铬污染对土壤细菌群落结构及其构建机制的影响

重金属铬污染场迁移过程受多种不确定因素影响，其迁移特性和监测过程很难通过实验进行研究。依据地下水流动基本规律和污染物迁移机理，采用COMSOL软件仿真分析静储量铬污染源的迁移特性及其变化规律，通过开展静态土槽物理模型实验，验证数值正演模拟的可靠性和准确性；以迁移模型为监测基础模型，采用中梯剖面和对称四极测深装置，对铬污染场迁移过程进行双频激电法监测数值正演模拟，分析平整、起伏地形和测点方位布置对监测效果的影响。结果表明：在铬污染物迁移过程中，高渗透系数的透水层对重污染区域表现出强烈的吸附效应，同时会在短时间内加剧污染区域的横向扩散；在视幅频率峰值和视电阻率谷值的异常对应关系上剖面探测要优于测深探测；对称四极测深时，在污染场的投影边缘中央设置测点可更有效地提高测量精度；在进行剖面和测深探测时，山谷会造成激电曲线出现“多峰”现象；在凸起山峰两侧山陲设置供电电极，通过视幅频率和视电阻率曲线可综合确定重度污染区域的具体位置。研究成果丰富了双频激电法对重金属土壤污染场监测的理论，为铬污染场实时监测提供理论依据和技术指导，对推动生态环境保护具有积极意义。

Chromium in drinking water: Sources,metabolism, and cancer risks

Given that the migration process of chromium-contaminated sites is subjected to various uncertainties, it is difficult to investigate the migration characteristics and explore the monitoring process using experiments. Based on the basic law of groundwater flow and the migration mechanisms of pollutants, this study conducted a simulation analysis of the migration characteristics of static chromium contamination sources and the law of changes in the migration characteristics using the COMSOL software. Then, this study verified the reliability and accuracy of numerical forward simulations through physical simulation experiments on a static soil bin. Specifically, using the model of chromium contamination source migration as a basic model for geoelectric monitoring, as well as the intermediate gradient detection device and symmetrical quadrupole sounding device, this study performed numerical forward simulations to monitor the migration process of chromium-contaminated sites with the dual-frequency induced polarization (IP) method. Accordingly, it analyzed the effects of flat and undulating terrains, as well as the orientations of measurement points, on the monitoring effects. The findings are as follows: (1) Permeable beds with high permeability coefficients produce strong adsorption effects for areas with severe chromium contamination during chromium pollutant migration. Meanwhile, these layers can intensify the lateral spreading of polluted areas in a short time. (2) Intermediate gradient detection device outperforms sounding detection in terms of the correspondence between the peaks of apparent amplitude frequency and the IP anomalies of the troughs of apparent resistivity curves. (3) The contamination monitoring accuracy of symmetrical quadrupole sounding can be enhanced by deploying measurement points in the middle of projected edges of contaminated sites. (4) The presence of valleys may induce multiple peaks in the IP curves during intermediate gradient detection and symmetrical quadrupole sounding. (5) By arranging power supply electrodes on the mountain frontiers on both sides of the mountain peaks, areas with severe chromium contamination can be comprehensively pinpointed using the curves of both apparent amplitude frequency and apparent resistivity. These findings enrich the theory of the monitoring of heavy metal-contaminated sites of soils using the dual-frequency IP method and provide theoretical and technical guidance for real-time monitoring of the sites, thus holding positive significance for promoting ecological protection.