California Department of Pesticide Regulation, Sacramento, CA, 95814, United States.
California Department of Pesticide Regulation, Sacramento, CA, 95814, United States.
Environ Pollut. 2018 Mar;234:48-58. doi: 10.1016/j.envpol.2017.11.032. Epub 2017 Nov 20.
Pesticides move to surface water via various pathways including surface runoff, spray drift and subsurface flow. Little is known about the relative contributions of surface runoff and spray drift in agricultural watersheds. This study develops a modeling framework to address the contribution of spray drift to the total loadings of pesticides in receiving water bodies. The modeling framework consists of a GIS module for identifying drift potential, the AgDRIFT model for simulating spray drift, and the Soil and Water Assessment Tool (SWAT) for simulating various hydrological and landscape processes including surface runoff and transport of pesticides. The modeling framework was applied on the Orestimba Creek Watershed, California. Monitoring data collected from daily samples were used for model evaluation. Pesticide mass deposition on the Orestimba Creek ranged from 0.08 to 6.09% of applied mass. Monitoring data suggests that surface runoff was the major pathway for pesticide entering water bodies, accounting for 76% of the annual loading; the rest 24% from spray drift. The results from the modeling framework showed 81 and 19%, respectively, for runoff and spray drift. Spray drift contributed over half of the mass loading during summer months. The slightly lower spray drift contribution as predicted by the modeling framework was mainly due to SWAT's under-prediction of pesticide mass loading during summer and over-prediction of the loading during winter. Although model simulations were associated with various sources of uncertainties, the overall performance of the modeling framework was satisfactory as evaluated by multiple statistics: for simulation of daily flow, the Nash-Sutcliffe Efficiency Coefficient (NSE) ranged from 0.61 to 0.74 and the percent bias (PBIAS) < 28%; for daily pesticide loading, NSE = 0.18 and PBIAS = -1.6%. This modeling framework will be useful for assessing the relative exposure from pesticides related to spray drift and runoff in receiving waters and the design of management practices for mitigating pesticide exposure within a watershed.
农药通过多种途径迁移到地表水，包括地表径流、喷雾漂移和地下水流。在农业流域中，人们对地表径流和喷雾漂移的相对贡献知之甚少。本研究开发了一个建模框架，以解决喷雾漂移对受纳水体中农药总负荷的贡献问题。该建模框架由一个用于识别漂移潜力的 GIS 模块、一个用于模拟喷雾漂移的 AgDRIFT 模型以及一个用于模拟各种水文和景观过程（包括地表径流和农药运移）的土壤和水评估工具（SWAT）组成。该建模框架应用于加利福尼亚州的奥雷斯蒂马溪流域。从每日样本中收集的监测数据用于模型评估。农药在奥雷斯蒂马溪上的质量沉积量为施用量的 0.08%至 6.09%。监测数据表明，地表径流是农药进入水体的主要途径，占年负荷的 76%；其余 24%来自喷雾漂移。建模框架的结果分别为 81%和 19%，分别为径流和喷雾漂移。在夏季，喷雾漂移对质量负荷的贡献超过一半。建模框架预测的喷雾漂移贡献略低，主要是由于 SWAT 在夏季对农药质量负荷的预测过低，而在冬季的预测过高。尽管模型模拟存在各种不确定性源，但通过多种统计数据评估，该建模框架的整体性能令人满意：对于日流量模拟，纳什-苏特克里夫效率系数（NSE）范围为 0.61 至 0.74，百分偏差（PBIAS）<28%；对于日农药负荷模拟，NSE=0.18，PBIAS=-1.6%。该建模框架将有助于评估与受纳水体中喷雾漂移和径流相关的农药的相对暴露风险，以及设计流域内减轻农药暴露的管理实践。
