Detection of herbicides in water bodies of the Samambaia River sub-basin in the Federal District and eastern Goiás

Abstract

The objective of this study was to identify and quantify herbicide residues in water samples of rain, cisterns, streams, ponds, springs, semi-artesian wells, dams and a river in the Rio Samambaia sub-basin in the Federal District and eastern Goiás. A total of 287 samples were collected from 20 farms in the sub-basin in the rainy (February, summer) and dry (August, winter) seasons in 2016. Aminomethylphosphonic acid (AMPA, a glyphosate metabolite), clethodim, chlorimuron-ethyl, diuron, fluazifop acid (a fluazifop-p-butyl metabolite and the active ingredient), haloxyfop acid (a haloxyfop-methyl metabolite and the active ingredient), imazamox, mesotrione, metsulfuron, nicosulfuron and pendimethalin were not identified in any water sample. In the rainy season, approximately 99% of the samples contained residues at least one of the evaluated herbicides; in the dry season (, 100% of the samples contained residues of at least one of the evaluated herbicides. When considering only detection frequency, metribuzin, atrazine, clomazone and haloxyfop-methyl were the main herbicides found in the water of the Samambaia River sub-basin. In turn, based on levels higher than the limit of quantification, the main compounds detected were atrazine, clomazone, haloxyfop-methyl and glyphosate. In both seasons, the highest relative concentrations of herbicides for the rainy and dry seasons were found in spring water, 25% and 56%, respectively, and dam water, 23% and 16%, respectively.