Department of Environmental Sciences, University of California, Riverside, California 92521, USA.
Environ Toxicol Chem. 2010 Jun;29(6):1203-8. doi: 10.1002/etc.184.
Contamination of surface aquatic systems by insecticides is an emerging concern in urban watersheds, but sources of contamination are poorly understood, hindering development of regulatory or mitigation strategies. Hardscapes such as concrete surfaces are considered an important facilitator for pesticide runoff following applications around homes. However, pesticide behavior on concrete has seldom been studied, and standardized evaluation methods are nonexistent. In the present study, a simple batch method for measuring pesticide wash-off potential from concrete surfaces was developed, and the dependence of washable pesticide residues was evaluated on pesticide types, formulations, time exposed to outdoor conditions, and number of washing cycles. After application to concrete, the washable fraction of four pyrethroids (bifenthrin, permethrin, cyfluthrin, and cyhalothrin) and fipronil rapidly decreased, with half-lives < or =3 d, likely due to irreversible retention in micropores below the concrete surface. The initial fast decrease was followed by a much slower declining phase with half-lives ranging from one week to two months, and detectable residues were still found in the wash-off solution for most treatments after 112 d. The slow decrease may be attributed to a fraction of pesticides being isolated from degradation or volatilization after retention below the concrete surface. Wash-off potential was consistently higher for solid formulations than for liquid formulations, implying an increased runoff contamination risk for granular and powder formulations. Trace levels of pyrethroids were detected in the wash-off solution even after 14 washing-drying cycles over 42 d under outdoor conditions. Results from the present study suggest that pesticide residues remain on concrete and are available for contaminating runoff for a prolonged time. Mechanisms for the long persistence were not clearly known from the present study and merit further investigation.
表面水生系统受到杀虫剂污染是城市流域中一个新出现的问题，但污染的来源还了解甚少，这阻碍了监管或缓解策略的制定。硬景观（如混凝土表面）被认为是家庭周围施药后农药径流的重要促进因素。然而，关于混凝土上农药的行为很少被研究，也没有标准化的评估方法。在本研究中，开发了一种简单的批量方法来测量混凝土表面的农药洗脱潜力，并评估了可洗去的农药残留对农药类型、配方、暴露于户外条件的时间和清洗循环次数的依赖性。施用于混凝土后，四种拟除虫菊酯（联苯菊酯、氯菊酯、氯氟氰菊酯和氯氰菊酯）和氟虫腈的可洗去部分迅速减少，半衰期 < 或 = 3 天，可能由于不可逆地保留在混凝土表面以下的微孔中。初始快速下降后，半衰期从一周到两个月不等的缓慢下降阶段，大多数处理在 112 天后仍能在洗脱溶液中检测到残留。缓慢的下降可能归因于一部分农药在保留在混凝土表面以下后与降解或挥发隔离。固体制剂的洗脱潜力始终高于液体制剂，这意味着颗粒状和粉状制剂的径流污染风险增加。即使在户外条件下经过 42 天、14 次洗涤-干燥循环后，洗脱溶液中仍检测到痕量的拟除虫菊酯。本研究结果表明，农药残留留在混凝土上，并可长时间用于污染径流。本研究尚不清楚导致长期持久性的机制，值得进一步研究。
