Stokdyk Joel, Firnstahl Aaron, Bradbury Kenneth, Muldoon Maureen, Kieke Burney, Borchardt Mark A
U.S. Geological Survey, Upper Midwest Water Science Center, Laboratory for Infectious Disease and the Environment, 2615 Yellowstone Drive, Marshfield, WI 54449, USA.
U.S. Geological Survey, Upper Midwest Water Science Center, Laboratory for Infectious Disease and the Environment, 2615 Yellowstone Drive, Marshfield, WI 54449, USA.
Water Res. 2025 May 1;275:123202. doi: 10.1016/j.watres.2025.123202. Epub 2025 Jan 25.
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.
家庭井水可能会受到来自地表污染物的影响而质量下降，但私人井水所有者缺乏保护水源免受周边干扰的手段。美国威斯康星州西南部的农村居民依赖私人井水，土地利用方式和破碎的碳酸盐基岩使得地下水容易受到污染。为了确定私人井水污染的程度、来源和风险因素，对秋季（n = 301）和春季（n = 529）在两天时间内随机抽取的井水样本进行了硝酸盐和指示菌分析，并且对一个子集（n = 138）在四个季节事件中进行了采样，通过定量聚合酶链反应分析病原体和微生物源追踪标记物。在多变量模型中分析了代表土地利用、水文、地质和水井建设的风险因素与污染之间的关联。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。硝酸盐污染与农业土地利用有关，套管延伸至页岩隔水层以下的水井所获取的水比从其上方取水的水井受污染程度更低。在64口水井（46%）中检测到了人类粪便微生物，降雨是污染的关键风险因素，这表明当运输条件有利时，化粪池系统的废水会污染水井。分别在33口和13口水井中检测到了来自牛/反刍动物和猪的粪便微生物，其浓度随着水井附近耕地面积的增加而升高。在66口水井（48%）中检测到了病毒、细菌和原生动物的病原体基因，其中人畜共患病原体的检测次数多于人类特异性病原体，而作为废水指示物的人类拟杆菌是私人井中病原体存在情况的一个不明确的预测指标。了解诸如地质等环境的重要因素，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层面政策提供参考。
