School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
Environ Toxicol Chem. 2020 Dec;39(12):2570-2587. doi: 10.1002/etc.4884. Epub 2020 Nov 10.
The temporal dynamics of pesticide concentrations in streams remains poorly characterized in southwestern Ontario, a region of the province where land use is dominated by agriculture. Understanding the magnitude and duration of pulsed exposures to pesticides in these small streams is critical when estimating the risk of pesticides to these aquatic ecosystems. The present study investigated the application of a high-frequency water sampling approach paired with the collection of flow data to characterize the pulsed exposure of pesticides to small streams in southwestern Ontario. Six sites along 2 different streams with different magnitudes of agricultural land use in their upstream catchments were sampled using half-day composite samples from July to October 2018 and from May to September 2019. A total of 1043 samples were collected over the 2 yr, of which 210 were analyzed. Samples for analysis were chosen based on flow, water level, and precipitation data. Liquid and gas chromatography coupled with tandem mass spectrometry was used to measure >500 pesticides in each water sample. A total of 35 different compounds were detected over the 6 sampling sites. For pesticides that were detected in >10% of water samples above the method quantification limit, a deterministic risk assessment using water quality guidelines and a probabilistic risk assessment using species sensitivity distributions were performed. The calculated hazard quotients showed that 2,4-D, atrazine, metolachlor, and metribuzin exceeded a level of concern of 1 at the highest concentrations detected. In all cases, hazard concentrations that would be protective of 95% of species from the species sensitivity distributions were greater than the 95th centile of the environmental exposure distributions, meaning that the risk from the pesticides was low. Environ Toxicol Chem 2020;39:2570-2587. © 2020 SETAC.
安大略省西南部地区的土地利用以农业为主，该地区溪流中农药浓度的时间动态仍未得到充分描述。了解这些小溪流中农药脉冲暴露的幅度和持续时间对于评估这些水生生态系统中农药的风险至关重要。本研究调查了一种高频水采样方法的应用，该方法与流量数据的收集相结合，以描述安大略省西南部小溪流中农药的脉冲暴露。在 2018 年 7 月至 10 月和 2019 年 5 月至 9 月期间，使用半每日组合样本对上游流域农业用地规模不同的 2 条不同溪流的 6 个地点进行采样。在 2 年期间共采集了 1043 个样本，其中 210 个进行了分析。根据流量、水位和降水数据选择用于分析的样本。液相和气相色谱串联质谱法用于测量每个水样中的>500 种农药。在 6 个采样点共检测到 35 种不同的化合物。对于在高于方法定量限的>10%水样中检测到的农药，如果使用水质准则进行确定性风险评估和使用物种敏感性分布进行概率风险评估，则进行评估。计算出的危害系数表明，2,4-D、莠去津、甲草胺和二甲戊灵在检测到的最高浓度下超过了 1 的关注水平。在所有情况下，保护物种敏感性分布中 95%物种的危害浓度都大于环境暴露分布的第 95 百分位数，这意味着农药的风险较低。Environ Toxicol Chem 2020;39:2570-2587。 © 2020 SETAC。
