Abstract Identification of sources of fecal pollution in urban areas is critical for protecting public health, the environment, and guiding remediation. We collected 670 water samples at 46 sites in 2018 to study fecal pollution in the Toronto Harbour and Don River watershed. Water samples were analyzed for E. coli, wastewater chemicals, and microbial source tracking DNA markers using a digital PCR technique. Microbial DNA markers were useful for interpreting the sources of elevated E. coli concentrations in the study. The HF183 marker for human sewage was the most frequently detected DNA marker, occurring in 100% of samples taken from the Don River and associated outfalls. It was also frequently detected in the Inner Harbour and outfalls along the Toronto harbour front. It was detected less frequently and at lower levels in the outer harbour. Detection of a human mitochondrial DNA marker and wastewater chemical markers such as caffeine provided additional evidence of widespread sewage contamination. The gull DNA marker was widely detected, but at lower frequencies and levels than human source DNA markers. A wet weather response of increased E. coli and human DNA marker concentrations occurred at most sites. However, human DNA markers were also widely detected on dry weather sampling days, indicating sewage cross-connections in stormwater and dry weather CSO systems. The cumulative impact of cross-connected stormwater outfalls is likely an under-recognized source of sewage contamination. E. coli and HF183 DNA marker levels observed can serve as benchmarks for evaluating future water quality improvements from wastewater infrastructure investments.

中文翻译：

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微生物源追踪以识别在潮湿和干燥天气中污染多伦多港和顿河流域的粪便源

摘要 城市地区粪便污染源的识别对于保护公众健康、环境和指导修复至关重要。2018 年，我们在 46 个地点收集了 670 个水样，以研究多伦多港和顿河流域的粪便污染。使用数字 PCR 技术分析水样中的大肠杆菌、废水化学品和微生物来源追踪 DNA 标记。微生物 DNA 标记可用于解释研究中大肠杆菌浓度升高的来源。人类污水的 HF183 标记物是最常检测到的 DNA 标记物，出现在 100% 从顿河和相关排污口采集的样本中。它也经常在内港和多伦多港口前沿的排放口中被发现。它在外港被检测到的频率较低且水平较低。人类线粒体 DNA 标记和废水化学标记（如咖啡因）的检测提供了广泛的污水污染的额外证据。海鸥 DNA 标记被广泛检测到，但频率和水平低于人类来源的 DNA 标记。大多数地点发生了大肠杆菌和人类 DNA 标记浓度增加的潮湿天气反应。然而，在干旱天气采样日也广泛检测到人类 DNA 标记，表明雨水和干旱天气 CSO 系统中的污水交叉连接。交叉连接的雨水排放口的累积影响可能是一个未被充分认识的污水污染源。观察到的大肠杆菌和 HF183 DNA 标记水平可作为评估未来废水基础设施投资改善水质的基准。