成都平原蔬菜生产中灌溉水对农药渗漏的影响研究

Effect of irrigation on pesticides leaching in vegetable farming in Chengdu plain using PEARL model

针对成都平原蔬菜生产中大量施用农药、大量灌水的特点,首次在国内应用欧洲官方成熟的农药评估模型——PEARL模型,研究评估了成都平原当前蔬菜生产中的灌溉方式对两种不同特性农药的渗漏的影响。杀毒矾(土壤吸附力(KOM)为0 L/kg,半衰期(DT50)为80 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是190μg.L-1,而有灌溉条件下其渗出质量浓度则可达523μg.L-1,是没有灌溉条件下的2.75倍。三唑磷(KOM为200 L.kg-1,DT50为60 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是0.025μg.L-1,而有灌溉条件下其渗出质量浓度为0.13μg.L-1,比没有灌溉时提高了4.2倍。不管有没有灌溉三唑磷在该地区对地下水的污染风险都很小,而杀毒矾的风险则很高。因此,农药的化学特性是影响农药渗漏的最重要的因子。在蔬菜生产中应尽量选用被土壤吸附力强、半衰期短的农药,例如:三唑磷;农药在土壤中的移动载体是土壤水,不合理的灌溉会大大地加大农药淋溶,应当多使用微喷、滴灌等节水灌溉措施,减少使用漫灌等耗水多的原始灌溉方式。

The aim of this study was to estimate the effects of irrigation on pesticide leaching in vegetable farming in the Chengdu plain. Leaching with and without irrigation was simulated for two different pesticides by using the PEARL model. In a system without irrigation, the simulated maximum concentration of oxadixyl （KOM is 0 L.kg^-1, DT50 is 80 days） under normal agricultural practice at 1 m depth was 190 μg.L^-1. Under irrigated circumstances the maximum Oxadixyl concentration at 1 m depth reached 523 μg.L^-1, which is 2.75 times higher. For Traizophos （KOM is 200 L.kg^-1 and DT50 is 60 days） the maximum simulated concentrations were 0.025 μg.L^-1 without irrigation and 0.13 μg.L^-1 with irrigation, which is 4.2 times higher than the concentration in the system without irrigation. The potential of ground water pollution by Traizophos in the study area is whereas the potential for pollution with Oxadixyl is estimated at very high. The main pesticide parameters that influence the pesticides leaching are the degradation velocity （expressed in half life in soil） and the sorption capacity （expressed in the horn）. A short half-life and a high Kom, is associated with low leaching risks; a long half life and a low Kom is associated with high leaching risks. Since water is the carrier of pesticides through the soil, the amount of irrigation water has high impact on pesticides leaching. Intensive flooding-irrigation increases the risks of pesticides leaching to ground water. The results suggest that adoption of micro-irrigation techniques as opposed to traditional flooding irrigation will reduce the risks of groundwater pollution with pesticides in the area.