The objective of this study was to evaluate and to monitor the presence of pesticides in the waters of the São Gonçalo channel and the Piratini river located in the southern region of the State of Rio Grande do Sul. During the rice growing season, water samples were collected five times, three samples from the river Piratini and four from the São Gonçalo canal. The methodology used for the analysis of residues of quinclorac, carbofuran and clomazone was the High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) and for residues of the pesticides fipronil and betacyfluthrin, the Gas Chromatography with Electron Capture Detection (GC-ECD) was used. Results show that from sowing to harvesting the quantity of pesticide residues in water decreased. It was also observed that, at the lowest point (Laranjal), a greater number of analyses contaminated with residues was detected (11 samples with some type of pesticide). Insecticide carbofuran and herbicide quinclorac were pesticides that presented residues more frequently (16 and 15 times, respectively). Clomazone and fipronil were present in each of the 7 samples with residues and betacyfluthrin was not detected at any site.
Gonçalo channel; Piratini River; herbicide; insecticide; water quality
