Department of Environmental Sciences, University of California, Riverside, California 92521, United States.
Environ Sci Technol. 2012 Jun 5;46(11):6028-34. doi: 10.1021/es300749p. Epub 2012 May 17.
Pesticides such as pyrethroids have been frequently found in runoff water from urban areas and the offsite movement is a significant cause for aquatic toxicities in urban streams and estuaries. To better understand the origination of pesticide residues in urban runoff, we investigated the association of pyrethroid residues with loose particles in runoff water from concrete surfaces after treatment with commercial products of bifenthrin and permethrin. In runoff water generated from simulated precipitations after 1 to 89 d exposure under dry outdoor conditions, over 80% of the pesticides was found on particles >0.7 μm for most treatments. The solid-water partitioning coefficient (K(d)) on day 1 was estimated to be 2.4 × 10(3) to 1.1 × 10(5) L/kg for permethrin and bifenthrin on these solids. Except for solid formulations, the pesticide-laden particles likely originated from dust particles preexisting on the concrete before treatment and the disintegration of the surficial concrete matter through weathering. We consequently tested a simple sponge-wipe method to collect and analyze the loose particles on concrete. Concurrent analyses (n = 30) showed an excellent linear correlation between the amount of pesticides transferrable to runoff water and that on the wipe (R(2) = 0.78, slope = 1.13 ± 0.11, P < 0.0001). The fact that the linear relationship has a slope close to 1.0 suggests that this method may be used to predict pesticide residues available for contaminating runoff water before runoff actually occurs. The importance of loose particles should be considered when developing practices to mitigate pesticide runoff contamination from urban residential areas.
城市地区径流水中经常会检测到拟除虫菊酯等农药，而这些农药的场外迁移是城市溪流和河口水生毒性的一个重要原因。为了更好地了解城市径流水中农药残留的来源，我们研究了在使用联苯菊酯和氯菊酯的商业产品处理后，混凝土表面径流水中与松散颗粒结合的拟除虫菊酯残留。在户外干燥条件下 1 至 89 天模拟降水产生的径流水中，对于大多数处理，超过 80%的农药存在于>0.7μm 的颗粒上。第 1 天的固-水分配系数（K(d)）估计为 1.1×10(5)至 2.4×10(3)L/kg，适用于这些固体上的氯菊酯和联苯菊酯。除了固体制剂外，载有农药的颗粒可能来自处理前混凝土表面预先存在的灰尘颗粒，以及通过风化使表面混凝土物质解体。因此，我们测试了一种简单的海绵擦拭方法来收集和分析混凝土上的松散颗粒。同时分析（n=30）显示，可转移到径流水中的农药量与擦拭物上的农药量之间存在极好的线性相关性（R(2)=0.78，斜率=1.13±0.11，P<0.0001）。线性关系的斜率接近 1.0，这一事实表明，在实际径流水发生之前，这种方法可以用于预测可用农药残留，从而污染径流水。在制定减轻城市住宅区农药径流污染的实践时，应考虑松散颗粒的重要性。
