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Sources and risk factors for nitrate, pathogens, and fecal contamination of private wells in rural southwestern Wisconsin, USA
Water Research ( IF 11.4 ) Pub Date : 2025-01-25 , DOI: 10.1016/j.watres.2025.123202
Joel Stokdyk, Aaron Firnstahl, Kenneth Bradbury, Maureen Muldoon, Burney Kieke, Mark A. Borchardt

Household well water can be degraded by contaminants from the land's surface, but private well owners lack means to protect the source water from neighboring disturbances. Rural residents of southwestern Wisconsin, USA, rely on private well water, and the combination of land use and fractured carbonate bedrock makes groundwater vulnerable to contamination. To identify the extent, sources, and risk factors of private well contamination, randomly selected wells sampled during two-day periods in fall (n = 301) and spring (n = 529) were analyzed for nitrate and indicator bacteria, and a subset (n = 138) was sampled across four seasonal events for analysis of pathogens and microbial source tracking markers by quantitative polymerase chain reaction. Risk factors representing land use, hydrology, geology, and well construction were analyzed for associations with contamination in multivariable models. The importance of risk factors varied by contaminant, illustrating the multifaceted nature of rural groundwater quality. Nitrate contamination was associated with agricultural land use, and wells with casings that extended below a shale aquitard accessed less contaminated water than those drawing water from above it. Human fecal microbes were detected in 64 wells (46%), and rainfall was the key risk factor for contamination, indicating that wastewater from septic systems was available to contaminate wells when transport conditions were favorable. Manure microbes from cattle/ruminants and pigs were detected in 33 and 13 wells, respectively, and concentrations increased with the hectarage of cultivated land near wells. Pathogen genes for viruses, bacteria, and protozoa were detected in 66 wells (48%), including more detections of zoonotic than human-specific pathogens, and human Bacteroides, an indicator of wastewater, was an equivocal predictor of pathogen presence in private wells. Characterizing important elements of the setting, like geology, and identifying sources and risk factors for contaminants can inform landscape-level policies to protect groundwater quality.

中文翻译:


美国威斯康星州西南部农村私人水井硝酸盐、病原体和粪便污染的来源和风险因素



家庭井水会因土地表面的污染物而降解,但私人井主缺乏保护源水免受邻近干扰的方法。美国威斯康星州西南部的农村居民依赖私人井水,土地利用和破裂的碳酸盐基岩相结合,使地下水容易受到污染。为了确定私人井污染的程度、来源和风险因素,在秋季 (n = 301) 和春季 (n = 529) 的两天期间随机选择采样的井中分析了硝酸盐和指示菌,并在四个季节性事件中对一个子集 (n = 138) 进行了采样,用于通过定量聚合酶链反应分析病原体和微生物来源追踪标志物。分析了代表土地利用、水文、地质和水井建设的风险因素与多变量模型中污染的关联。风险因素的重要性因污染物而异,这说明了农村地下水质量的多面性。硝酸盐污染与农业用地有关,与从页岩滞水层上方取水的井相比,带有套管延伸到页岩滞水层下方的井获得的受污染水更少。在 64 口井 (46%) 中检测到人类粪便微生物,降雨是污染的关键风险因素,这表明当运输条件有利时,来自化粪池系统的废水可以污染水井。分别在 33 口和 13 口井中检测到来自牛/反刍动物和猪的粪便微生物,浓度随着井附近耕地的公顷数而增加。 在 66 口井中检测到病毒、细菌和原生动物的病原体基因 (48%),其中检测到的人畜共患病原体多于人类特异性病原体,而人类拟杆菌(废水的指标)是私人井中存在病原体的模棱两可的预测因子。描述环境的重要元素(如地质)并确定污染物的来源和风险因素可以为保护地下水质量的景观级政策提供信息。
更新日期:2025-01-25
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