农田尺度降雨入渗—重分布条件下阿特拉津在非饱和土壤中淋溶风险的评价

RISK ASSESSMENT OF ATRAZINE LEACHING IN SOIL AT FIELD SCALE LEVEL

以农药阿特拉津为研究对象,通过在北京郊区一个面积为72 9m2 (2 7m×2 7m)的田间采集10 0个土壤样品,分别测定其主要理化特性,由土壤的机械组成和干容重测试数据,采用土壤传递函数生成了vanGenuchten型的水力学参数,并进一步间接计算得到阿特拉津运移的弥散度,同时,由实测的土壤有机碳含量估算了阿特拉津的吸附参数。在此基础上,根据柱模型假设,运用HYDRUS 1D软件,就所设计的由实际背景概化而来的降雨入渗—重分布算例,对阿特拉津在农田尺度非饱和土壤中的淋溶动态进行了数值模拟。结果表明:对一场雨量为90mm、雨强为30mmd-1的降雨,在连续3d降雨接着重分布2 0d的情况下,若忽略蒸散作用对土壤水分和阿特拉津运动的影响,则降雨入渗和降雨入渗—重分布过程结束时,通过土壤2 0cm耕层的阿特拉津的最大累积淋溶量分别占施用量的17.87%和75 .4 1% ;采样区域内阿特拉津淋溶通量的空间分布存在较大差异。所探明的阿特拉津易淋溶带,不仅为合理使用该农药、保护土壤环境提供了定量的依据。

Risk assessment of leaching of pesticides at field scale level is of importance to protection of the groundwater environment. In this study, a total of 100 soil samples were taken from a field plot (27 m×27 m), which was located in the suburbs of Beijing. Some physico chemical properties were analyzed of all the samples. By means of soil pedotransfer function, van Genuchten type's hydraulic parameters were generated from measured values of soil particle size fraction and soil bulk density using ROSETTA code. Dispersivities of atrazine were indirectly obtained from water retention curves, and adsorption coefficients of atrazine in different samples were estimated based on measured soil organic carbon content. And then, according to the column model based assumption, and with the aid of HYDRUS 1D software, the infiltration redistribution process simplified from the actual background was simulated for evaluating the maximum risk of atrazine leaching through the unsaturated soil. The results show that, under the condition of a rainfall lasting 3 days with precipitation being 90 mm and intensity 30 mm d -1 and 20 days of redistribution afterwards, if the effect of evapotranspiration on soil water movement and atrazine transport was negligible, the maximum cumulative amount of atrazine leaching down through the tillage layer (20 cm) was 17.87% and 75.41% of the applied dose, respectively, at the end of the infiltration and of the infiltration redistribution processes, and spatial variation of the distribution of leaching flux of atrazine in the sampled area was quite different. The predicted vulnerable zone of atrazine leaching can not only provide quantitative basis for rationalizing use of the pesticide for the sake of environment protection, but also supply important information for preventing shallow groundwater from atrazine contamination.