Holman I P, Dubus I G, Hollis J M, Brown C D
Cranfield University at Silsoe, Silsoe, Bedford MK45 4DT, UK.
Sci Total Environ. 2004 Jan 5;318(1-3):73-88. doi: 10.1016/S0048-9697(03)00375-9.
Although macropore flow is recognized as an important process for the transport of pesticides through a wide range of soils, none of the existing spatially distributed methods for assessing the risk of pesticide leaching to groundwater account for this phenomenon. The present paper presents a spatially distributed modelling system for predicting pesticide losses to groundwater through micro- and macropore flow paths. The system combines a meta version of the mechanistic, dual porosity, preferential flow pesticide leaching model MACRO (the MACRO emulator), which describes pesticide transport and attenuation in the soil zone, to an attenuation factor leaching model for the unsaturated zone. The development of the emulator was based on the results of over 4000 MACRO model simulations. Model runs describe pesticide leaching for the range of soil types, climate regimes, pesticide properties and application patterns in England and Wales. Linking the MACRO emulator to existing spatial databases of soil, climate and compound-specific loads allowed the prediction of the concentration of pesticide leaching from the base of the soil profile (at 1 m depth) for a wide range of pesticides. Attenuation and retardation of the pesticide during transit through the unsaturated zone to the watertable was simulated using the substrate attenuation factor model AQUAT. The MACRO emulator simulated pesticide loss in 10 of 12 lysimeter soil-pesticide combinations, for which pesticide leaching was shown to occur and also successfully predicted no loss from 3 soil-pesticide combinations. Although the qualitative aspect of leaching was satisfactorily predicted, actual pesticide concentrations in leachate were relatively poorly predicted. At the national scale, the linked MACRO emulator/AQUAT system was found to predict the relative order of, and realistic regional patterns of, pesticide leaching for atrazine, isoproturon, chlorotoluron and lindane. The methodology provides a first-step assessment of the potential for pesticide leaching to groundwater in England and Wales. Further research is required to improve the modelling concept proposed. The system can be used to refine regional groundwater monitoring system designs and sampling strategies and improve the cost-effectiveness of the measures needed to achieve 'good status' of groundwater quality as required by the Water Framework Directive.
尽管大孔隙流被认为是农药在多种土壤中迁移的一个重要过程，但现有的用于评估农药淋溶至地下水风险的空间分布方法均未考虑这一现象。本文提出了一种空间分布建模系统，用于预测农药通过微孔和大孔隙流路径向地下水的流失。该系统将描述土壤层中农药迁移和衰减的机理型双孔隙优先流农药淋溶模型MACRO的元版本（MACRO模拟器）与非饱和带的衰减因子淋溶模型相结合。模拟器的开发基于4000多次MACRO模型模拟的结果。模型运行描述了英格兰和威尔士土壤类型、气候条件、农药特性及施用模式范围内的农药淋溶情况。将MACRO模拟器与现有的土壤、气候和特定化合物负荷空间数据库相链接，能够预测多种农药从土壤剖面底部（1米深度）淋溶的浓度。使用底物衰减因子模型AQUAT模拟了农药在通过非饱和带到达地下水位过程中的衰减和阻滞情况。MACRO模拟器在12个蒸渗仪土壤 - 农药组合中的10个中模拟了农药流失情况，这些组合显示出农药淋溶现象，并且还成功预测了3个土壤 - 农药组合无农药流失。虽然淋溶的定性方面得到了令人满意的预测，但渗滤液中实际农药浓度的预测相对较差。在国家尺度上，发现链接的MACRO模拟器/AQUAT系统能够预测阿特拉津、异丙隆、绿麦隆和林丹的农药淋溶的相对顺序及实际区域模式。该方法为英格兰和威尔士农药淋溶至地下水的可能性提供了初步评估。需要进一步研究以改进所提出的确建模概念。该系统可用于完善区域地下水监测系统设计和采样策略，并提高实现《水框架指令》要求的地下水质量“良好状态”所需措施的成本效益。
