Rain events may impact the chemical pollution burden in rivers. Forty-four small streams in Germany were profiled during several rain events for the presence of 395 chemicals and five types of mixture effects in in vitro bioassays (cytotoxicity; activation of the estrogen, aryl hydrocarbon, and peroxisome proliferator-activated receptors; and oxidative stress response). While these streams were selected to cover a wide range of agricultural impacts, in addition to the expected pesticides, wastewater-derived chemicals and chemicals typical for street runoff were detected. The unexpectedly high estrogenic effects in many samples indicated the impact by wastewater or overflow of combined sewer systems. The 128 water samples exhibited a high diversity of chemical and effect patterns, even for different rain events at the same site. The detected 290 chemicals explained only a small fraction (<8%) of the measured effects. The experimental effects of the designed mixtures of detected chemicals that were expected to dominate the mixture effects of detected chemicals were consistent with predictions for concentration addition within a factor of two for 94% of the mixtures. Overall, the burden of chemicals and effects was much higher than that previously detected in surface water during dry weather, with the effects often exceeding proposed effect-based trigger values.

中文翻译：

---

在降雨事件期间，在小型农业流中进行的化学品的体外生物测定中评估混合物的效果。

降雨事件可能会影响河流中的化学污染负担。在几次降雨事件中，对德国的44条小溪进行了剖析，得出395种化学物质的存在和5种体外混合效应生物测定（细胞毒性；雌激素，芳基烃和过氧化物酶体增殖物激活受体的激活；氧化应激反应）。选择这些河流以覆盖广泛的农业影响，除了预期的农药外，还检测到废水衍生的化学品和典型的街道径流化学品。许多样品中出乎意料的高雌激素效应表明废水或联合下水道系统溢流的影响。128个水样本即使在同一地点发生不同的降雨事件时，也表现出高度的化学和效应模式多样性。所检测到的290种化学物质仅解释了所测效果的一小部分（<8％）。预期将主要控制所检测化学物质的混合物效应的所检测化学物质的设计混合物的实验效果与94％混合物中浓度增加值在2的预测相一致。总体而言，化学物和效应的负担比干燥天气期间先前在地表水中检测到的负担要高得多，其效应通常超过了基于效应的建议触发值。