Lerch R N, Blanchard P E
USDA-Agricultural Research Service, Cropping Systems and Water Quality Research Unit, 269 Agricultural Engineering Building, University of Missouri, Columbia, Missouri 65211, USA.
Environ Sci Technol. 2003 Dec 15;37(24):5518-27. doi: 10.1021/es030431s.
Herbicide contamination of streams has been well documented, but little is currently known about the specific factors affecting watershed vulnerability to herbicide transport. The primary objectives of this study were (1) to document herbicide occurrence and transport from watersheds in the northern Missouri/southern Iowa region; (2) to quantify watershed vulnerability to herbicide transport and relate vulnerability to soil properties; and (3) to compute the contribution of this region to the herbicide load of the Missouri and Mississippi Rivers. Grab samples were collected under baseflow and runoff conditions at 21 hydrologic monitoring stations between April 15 and July 15 from 1996 to 1999. Samples were analyzed for commonly used soil-applied herbicides (atrazine, cyanazine, acetochlor, alachlor, metolachlor, and metribuzin) and four triazine metabolites (deisopropylatrazine, deethylatrazine, hydroxyatrazine, and cyanazine amide). Estimates of herbicide load and relative losses were computed for each watershed. Median parent herbicide losses, as a percentage of applied, ranged from 0.33 to 3.9%; loss rates that were considerably higher than other areas of the United States. Watershed vulnerability to herbicide transport, measured as herbicide load per treated area, showed that the runoff potential of soils was a critical factor affecting herbicide transport. Herbicide transport from these watersheds contributed a disproportionately high amount of the herbicide load to both the Missouri and Mississippi Rivers. Based on these results, this region of the Corn Belt is highly vulnerable to transport of herbicides from fields to streams, and it should be targeted for implementation of management practices designed to reduce herbicide losses in surface runoff.
溪流受到除草剂污染的情况已有充分记录，但目前对于影响流域对除草剂迁移脆弱性的具体因素知之甚少。本研究的主要目标是：（1）记录密苏里州北部/爱荷华州南部地区流域中除草剂的存在情况及其迁移；（2）量化流域对除草剂迁移的脆弱性，并将脆弱性与土壤特性相关联；（3）计算该地区对密苏里河和密西西比河除草剂负荷的贡献。在1996年至1999年4月15日至7月15日期间，在21个水文监测站的基流和径流条件下采集了抓取样本。对样本分析了常用的土壤施用除草剂（阿特拉津、氰草津、乙草胺、甲草胺、异丙甲草胺和嗪草酮）以及四种三嗪代谢物（去异丙基阿特拉津、去乙基阿特拉津、羟基阿特拉津和氰草津酰胺）。计算了每个流域的除草剂负荷估计值和相对损失。母体除草剂损失中位数（占施用量的百分比）在0.33%至3.9%之间；损失率远高于美国其他地区。以每处理面积的除草剂负荷衡量的流域对除草剂迁移的脆弱性表明，土壤的径流潜力是影响除草剂迁移的关键因素。这些流域的除草剂迁移对密苏里河和密西西比河的除草剂负荷贡献比例过高。基于这些结果，玉米带的这个地区极易受到除草剂从农田向溪流迁移的影响，应将其作为实施旨在减少地表径流中除草剂损失的管理措施的目标区域。
