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J Environ Qual. 2020 Jan;49(1):152-162. doi: 10.1002/jeq2.20045.
Pesticides are important for agriculture in the United States, and atrazine is one of the most widely used and widely detected pesticides in surface water. A better understanding of the mechanisms by which atrazine and its degradation product, deethylatrazine, increase and decrease in surface waters can help inform future decisions for water quality improvement. This study considers causal factors for trends in pesticide concentration in U.S. streams and models the causal factors, other than use, in structural equation models. The structural equation models use a concomitant trend in corn (Zea mays L.) and a latent variable model, indicating moisture supply and management. The moisture supply and management latent variable model incorporates long-term moisture conditions in the individual watersheds by using the Palmer hydrologic drought index, human influence on the hydrologic cycle through the percentage of the watershed drained by tile drains in 2012, and the base-flow contribution to streamflow, using the base-flow index. The structural equation models explain 77 and 38% of the variability in atrazine and deethylatrazine trends, respectively, across the conterminous United States. The models highlight future water quality challenges, particularly in tile-drained settings where fall precipitation and heavy precipitation are increasing.
农药在美国农业中非常重要，而莠去津是地表水中使用最广泛、检测最广泛的农药之一。更好地了解莠去津及其降解产物去乙基莠去津在地表水中增加和减少的机制，可以为未来的水质改善决策提供信息。本研究考虑了美国溪流中农药浓度变化的因果因素，并在结构方程模型中对除使用之外的因果因素进行了建模。结构方程模型使用玉米（Zea mays L.）的伴随趋势和一个潜在变量模型，表明水分供应和管理。水分供应和管理潜在变量模型通过使用帕尔默水旱指数来整合各个流域的长期水分条件，通过 2012 年流域排水面积的百分比来整合人类对水文循环的影响，以及使用基流指数来整合基流对河流流量的贡献。结构方程模型分别解释了美国大陆地区莠去津和去乙基莠去津趋势变化的 77%和 38%。这些模型突出了未来的水质挑战，特别是在排水瓷砖的环境中，秋季降水和强降水正在增加。
