Occurrence of glyphosate and AMPA in an agricultural watershed from the southeastern region of Argentina

LUPI LEONARDO; MIGLIORANZA, KARINA SILVIA BEATRIZ; APARICIO VIRGINIA; MARINO DAMIAN; BEDMAR FRANCISCO; WUNDERLIN DANIEL A.

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 536 p. 687 - 694

0048-9697

Glyphosate (GLY) and AMPA concentrations were determined in sandy soil profiles, during pre- and post-application events in two agricultural soybean fields (S1 and S2). Streamwater and sediment samples werealso analyzed. Post-application sampling was carried out one month later from the event. Concentrations ofGLY + AMPA in surface soils (0?5 cm depth) during pre-application period showed values 20-fold higher(0.093?0.163 μg/g d.w.) than control area (0.005 μg/g d.w.). After application event soils showed markedly higherpesticide concentrations. A predominance of AMPA (80%) was observed in S1 (early application), while 34% in S2for surface soils. GLY + AMPA concentrations decreased with depth and correlated strongly with organic carbon(r between 0.74 and 0.88, p b 0.05) and pH (r between −0.81 and −0.76, p b 0.001). The slight enrichment ofpesticides observed from 25 cm depth to deeper layer, in addition to the alkaline pH along the profile, is ofhigh concern about groundwater contamination. Sediments from pre-application period showed relativelylower pesticide levels (0.0053?0.0263 μg/g d.w.) than surface soil with a predominance of glyphosate, indicatinga limited degradation. Levels of contaminants (mainly AMPA) in streamwater (ND-0.5 ng/mL) denote the lowpersistence of these compounds. However, a direct relationship in AMPA concentration was observed betweensediment and streamwater. Despite the known relatively short half-life of glyphosate in soils, GLY + AMPA oc-currence is registered in almost all matrices at different sampling times (pre- and post-application events). Thephysicochemical characteristics (organic carbon, texture, pH) and structure of soils and sediment in addition tothe time elapsed from application determined the behavior of these contaminants in the environment. As awhole, the results warn us about vertical transport trough soil profile with the possibility of reachinggroundwater.