Abstract

A significant proportion of the pesticides that are widely used in agriculture are highly toxic pollutants, despite their low concentrations. They have high capacity for polluting water, soil and air,especially during their application. The difficulty and cost of analyses to identify them and the inefficiency of conventional water treatment for human consumption,combined with the lack of legislation on this subject, has favored their accumulation in the environment. The present study was conducted in the lower part of the São Francisco River, in Brazil, between the Xingo hydroelectric power plant (municipality of Piranhas, Alagoas State [AL]) and the mouth of the river (municipality of Piacabucu, Alagoas State [AL]).This stretch of the river is approximately 240 km long. Water was sampled in November 2021, at transects downstream from the municipalities of Piranhas AL, Pao de Acucar AL, Traipu AL, Sao Bras AL, Propria (Sergipe State) and Penedo AL. The technique used for analytical monitoring was gas chromatography coupled to mass spectrometry (GC-MS).The presence of 14 pesticides was detected, among the 31 that were evaluated. Among the compounds identified,three are classified as extremely toxic, six are classified as highly toxic and five are classified as moderately toxic. The presence of three compounds was identified in the municipality of Pao de Acucar and two of these were highly toxic.In Traipu, there were four compounds, among which one was extremely toxic and two were highly toxic. In Sao Bras,there were four compounds, among which three were the same as found in Traipu. Propria and Penedo presented the highest diversity of pesticide contaminants, respectively nine and ten pollutants.