Agricultural and Environmental Chemistry Graduate Group, University of California, Davis, California, USA.
Environ Toxicol Chem. 2013 Dec;32(12):2686-94. doi: 10.1002/etc.2347. Epub 2013 Oct 18.
Although the freely dissolved form of hydrophobic organic chemicals may best predict aquatic toxicity, differentiating between dissolved and particle-bound forms is challenging at environmentally relevant concentrations for compounds with low toxicity thresholds such as pyrethroid insecticides. The authors investigated the distribution of pyrethroids among 3 forms: freely dissolved, complexed with dissolved organic carbon, and sorbed to suspended particulate matter, during a yearlong study at a secondary wastewater treatment plant. Effluent was fractionated by laboratory centrifugation to determine whether sorption was driven by particle size. Linear distribution coefficients were estimated for pyrethroid sorption to suspended particulate matter (K(id)) and dissolved organic carbon (K(idoc)) at environmentally relevant pyrethroid concentrations. Resulting K(id) values were higher than those reported for other environmental solids, and variation between sampling events correlated well with available particle surface area. Fractionation results suggest that no more than 40% of the pyrethroid remaining in secondary effluent could be removed by extending settling periods. Less than 6% of the total pyrethroid load in wastewater effluent was present in the dissolved form across all sampling events and chemicals.
尽管疏水性有机化学品的自由溶解形式可能最能预测水生毒性，但对于毒性阈值较低的化合物（如拟除虫菊酯类杀虫剂），在环境相关浓度下区分溶解和颗粒结合形式具有挑战性。作者在一个二级污水处理厂进行了为期一年的研究，调查了拟除虫菊酯在 3 种形式之间的分布：自由溶解、与溶解有机碳络合和被悬浮颗粒物吸附。通过实验室离心对废水进行分级，以确定吸附是否由粒径驱动。在环境相关的拟除虫菊酯浓度下，估算了拟除虫菊酯对悬浮颗粒物（K(id)）和溶解有机碳（K(idoc)）的吸附线性分布系数。得出的 K(id)值高于其他环境固体物质的报道值，并且采样事件之间的变化与可用的颗粒表面积很好地相关。分级结果表明，通过延长沉降时间，只能去除二级出水中不超过 40%的拟除虫菊酯。在所有采样事件和化学物质中，废水中总拟除虫菊酯负荷中只有不到 6%以溶解形式存在。
