Elias Daniel, Bernot Melody J
Department of Biology, Ball State University, 2000 W. University Ave. CL121, Muncie, IN, USA.
Environ Monit Assess. 2017 Apr;189(4):162. doi: 10.1007/s10661-017-5870-1. Epub 2017 Mar 14.
Agrochemicals can be transported from agricultural fields into streams where they might have adverse effects on water quality and ecosystems. Three enrichment experiments were conducted in a central Indiana stream to quantify pesticide and nitrogen transport dynamics. In an enrichment experiment, a compound solution is added at a constant rate into a stream to increase compound background concentration. A conservative tracer (e.g., bromide) is added to determine discharge. Water and sediment samples are taken at several locations downstream to measure uptake metrics. We assessed transport of nitrate, atrazine, metolachlor, and carbaryl through direct measurement of uptake length (S ), uptake velocity (V ), and areal uptake (U). S measures the distance traveled by a nutrient along the stream reach. V measures the velocity a nutrient moves from the water column to immobilization sites. U represents the amount of nutrient immobilized in an area of streambed per unit of time. S varied less than one order of magnitude across pesticides. The highest S for atrazine suggests greater transport to downstream ecosystems. Across compounds, pesticide S was longest in August relative to October and July. V varied less than one order of magnitude across pesticides with the highest V for metolachlor. U varied three orders of magnitude across pesticides with the highest U associate with sediment-bound carbaryl. Increasing nitrate S suggests a lower nitrate demand of biota in this stream. Overall, pesticide transport was best predicted by compound solubility which can complement and improve models of pesticide abundance used by water quality programs and risk assessments.
农用化学品可从农田流入溪流，进而可能对水质和生态系统产生不利影响。在印第安纳州中部的一条溪流中进行了三项富集实验，以量化农药和氮的迁移动态。在富集实验中，将复合溶液以恒定速率添加到溪流中，以提高复合背景浓度。添加一种保守示踪剂（如溴化物）来测定流量。在下游的几个位置采集水和沉积物样本，以测量吸收指标。我们通过直接测量吸收长度（S ）、吸收速度（V ）和面积吸收量（U）来评估硝酸盐、阿特拉津、异丙甲草胺和西维因的迁移情况。S 测量养分沿溪流河段移动的距离。V 测量养分从水柱移动到固定位点的速度。U表示单位时间内固定在河床单位面积上的养分数量。不同农药的S 变化小于一个数量级。阿特拉津的最高S 表明其向下游生态系统的迁移能力更强。在不同化合物中，8月份的农药S 相对于10月和7月最长。不同农药的V 变化小于一个数量级，异丙甲草胺的V 最高。不同农药的U变化三个数量级，沉积物结合态西维因的U最高。硝酸盐S 的增加表明该溪流中生物群对硝酸盐的需求较低。总体而言，农药迁移最好通过化合物溶解度来预测，这可以补充和改进水质计划和风险评估中使用的农药丰度模型。
