Seasonal and spatial variations of glyphosate in surface waters of Crespo stream, Buenos Aires province, Argentina

PÉREZ, DÉBORA JESABEL; OKADA, ELENA; APARICIO, VIRGINIA; MENONE, MIRTA LUJÁN; COSTA, JOSE LUIS

Buenos Aires

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

SETAC

El Crespo stream is located inside a small watershed (52,000 Ha) which is only influenced by farming activities without urban or industrial impact. The watershed can be divided in two areas, the southern area (upstream), mainly composed of intensive crops and the northern area (downstream) used only for extensive livestock. In this sense, ?El Crespo? stream in an optimal site for monitoring screening of pesticide residues. The objective of this work was to determine the seasonal and spatial variations of glyphosate (GLY), in surface waters of ?El Crespo? stream. We hypothesized that in surface waters of ?El Crespo? stream the levels of GLY vary depending of the season and rainfall events. The water sampling was carried out from October to June (2014-2015) in two sites: upstream (US) and downstream (DS), before and after rain events. The water samples were collected by triplicate in 1 L polypropylene bottles and stored at -20°C until analysis. GLY was extracted from unfiltered water samples with a buffer solution (100 mM Na2B4O7·10H2O/100 mM K3PO4, pH=9) and derivatized with 9-fluorenylmethylchloroformate (1 mg/mL in acetonitrile). Afterwards samples were analyzed using liquid chromatography coupled to a tandem mass spectrometer (UPLC-MS/MS). The detection limit (LD) was 0.1 g/L and the quantification limit (QL) was 0.5 g/L. The rainfall regime was obtained from the database of INTA Balcarce. GLY was detected in 92.3% of the analyzed samples. In the US site, were GLY is regularly applied, the highest GLY concentration was registered in October (2.15 ± 0.16 g/L); from November to June, the GLY levels decreased from 1.97 ± 0.17 g/L to