Department of Geochemistry, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1300 Copenhagen K, Denmark.
Chemosphere. 2011 Jul;84(4):471-9. doi: 10.1016/j.chemosphere.2011.03.029. Epub 2011 Apr 9.
Leaching of the strongly sorbing pesticides glyphosate and pendimethalin was evaluated in an 8-month field study focussing on preferential flow and particle-facilitated transport, both of which may enhance the leaching of such pesticides in structured soils. Glyphosate mainly sorbs to mineral sorption sites, while pendimethalin mainly sorbs to organic sorption sites. The two pesticides were applied in equal dosage to a structured, tile-drained soil, and the concentration of the pesticides was then measured in drainage water sampled flow-proportionally. The leaching pattern of glyphosate resembled that of pendimethalin, suggesting that the leaching potential of pesticides sorbed to either the inorganic or organic soil fractions is high in structured soils. Both glyphosate and pendimethalin leached from the root zone, with the average concentration in the drainage water being 3.5 and 2.7 μg L(-1), respectively. Particle-facilitated transport (particles >0.24 μm) accounted for only a small proportion of the observed leaching (13-16% for glyphosate and 16-31% for pendimethalin). Drain-connected macropores located above or in the vicinity of the drains facilitated very rapid transport of pesticide to the drains. That the concentration of glyphosate and pendimethalin in the drainage water remained high (>0.1 μg L(-1)) for up to 7d after a precipitation event indicates that macropores between the drains connected to underlying fractures were able to transport strongly sorbing pesticides in the dissolved phase. Lateral transport of dissolved pesticide via such discontinuities implies that strongly sorbing pesticides such as glyphosate and pendimethalin could potentially be present in high concentrations (>0.1 μg L(-1)) in both water originating from the drainage system and the shallow groundwater located at the depth of the drainage system.
在一项为期 8 个月的野外研究中评估了强吸附性农药草甘膦和二甲戊灵的浸出情况，该研究重点关注优先流和颗粒促进的迁移，这两种过程都可能增强结构土壤中此类农药的浸出。草甘膦主要吸附在矿物吸附位上，而二甲戊灵主要吸附在有机吸附位上。两种农药以等量施用于结构紧实、有排水瓦管的土壤，并按比例采集排水以测量其中的农药浓度。草甘膦的浸出模式与二甲戊灵相似，这表明吸附在无机或有机土壤部分的农药的浸出潜力在结构土壤中很高。草甘膦和二甲戊灵都从根区淋出，排水水中的平均浓度分别为 3.5 和 2.7μg/L。颗粒促进的迁移（粒径＞0.24μm）仅占观察到的浸出量的一小部分（草甘膦为 13-16%，二甲戊灵为 16-31%）。位于排水渠上方或附近的与排水渠相连的排水连通大孔促进了农药向排水渠的快速迁移。草甘膦和二甲戊灵在排水水中的浓度在降水事件后长达 7 天仍保持较高水平（＞0.1μg/L），这表明排水渠之间与下方裂缝相连的大孔能够以溶解相运输强吸附性农药。通过这种不连续性的溶解农药的侧向迁移意味着强吸附性农药（如草甘膦和二甲戊灵）可能以高浓度（＞0.1μg/L）存在于源自排水系统的水中和位于排水系统深度的浅层地下水中。
