The total cultivated area in Brazil reached to 62 million ha in 2018, with the predominance of genetically modified soybean and corn (36 and 17 million ha, respectively) in no-tillage systems. In 2018, 5.3 × 105 Mg of active ingredient of pesticides was applied in cropfields, representing about 7.3 L of commercial product by habitant. However, the monitoring of water courses contamination by pesticides remains scarce and is based on traditional grab sampling systems. In this study, we used the grab (water) and passive sampling (Polar Organic Chemical Integrative Sampler-POCIS) to monitor pesticide contamination in the river network of a representative agricultural catchment of southern Brazil. We selected 18 sampling sites located in tributaries and in the main course of the Guaporé River, in Rio Grande do Sul State, with different land use predominance including forest, urban, and agricultural areas. Altogether, 79 and 23 pesticides were, respectively, analyzed in water and POCIS samples. The water of Guaporé River and its tributaries were highly contaminated by many pesticides, especially by four herbicides (2,4-D, atrazine, deethyl-atrazine, and simazine), three fungicides (carbendazim, tebuconazole, and epoxiconazole), and one insecticide (imidacloprid). The amount, type, and concentration of pesticides detected were completely different depending on the sampling technic used. POCIS was effective to discriminate the contamination according to the main land use of each sampling site. The monitored areas with the predominance of soybean cultivation under no-tillage tended to have higher concentrations of fungicide, while in the more diversified region, the herbicides showed higher values. The presence of five herbicides used in corn and grassland forage production was correlated with areas of integrated crop-livestock systems, in contrast to higher contamination by 2,4-D in areas of intensive production of soybean and winter cereals.

中文翻译：

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“现代农业”将许多农药转移到河道中：以巴西南部一个有代表性的农村流域为例。

2018年，巴西的总耕种面积达到6200万公顷，其中转基因大豆和玉米（分别为36和1700万公顷）在免耕系统中占主导地位。2018年，在农田中施用了5.3×105 Mg的农药有效成分，居民使用的商品约占7.3 L. 但是，对农药对水道污染的监测仍然很少，并且是基于传统的抓斗采样系统。在这项研究中，我们使用了抓取（水）和被动采样（Polar有机化学综合采样器-POCIS）来监测巴西南部一个典型农业流域的河网中的农药污染。我们选择了位于南里奥格兰德州瓜瓜雷河支流和支流的18个采样点，具有不同的土地利用优势，包括森林，城市和农业地区。在水和POCIS样品中分别分析了79种和23种农药。瓜珀雷河及其支流的水受到许多农药的高度污染，特别是四种除草剂（2,4-D，阿特拉津，去乙基阿特拉津和西玛津），三种杀真菌剂（多菌灵，戊唑醇和环氧环唑）和一种杀虫剂（吡虫啉）。根据所使用的采样技术，检测到的农药的数量，类型和浓度完全不同。POCIS有效地根据每个采样点的主要土地用途来区分污染。在免耕条件下以大豆种植为主的受监测地区，杀菌剂的浓度往往较高，而在更多样化的地区，除草剂显示出更高的价值。玉米和草原牧草生产中使用的五种除草剂的存在与农作物－牲畜综合系统的面积相关，而大豆和冬季谷物的集约化生产区域中2,4-D的污染较高。