Assessing the vulnerability of groundwater resources in semiarid lands of central Argentina

Groundwater resources in semiarid lands of central Argentina are currently threatened by contamination from agricultural pesticides. The objectives of the present work were: (a) to estimate groundwater recharge on a monthly basis to identify periods of high susceptibility of the aquifers to be polluted, (b) to assess groundwater vulnerability to pollution using the Generic and Pesticides DRASTIC GIS-based model for each recharge month previously identified, (c) to quantify the presence of atrazine, imazapyr, glyphosate, and its metabolite AMPA in groundwater, and (d) to check the application of the DRASTIC model in the semiarid lands of central Argentina. According to the estimation of groundwater recharge, the vulnerability of aquifers increases during March, April, and November. The six resultant vulnerability maps revealed that groundwater is under “high-to-moderate” risk of pollution in the study area. About 47 and 88% of the total area is highly vulnerable, according to the Generic and Pesticides DRASTIC maps, respectively. Atrazine and imazapyr were quantified in groundwater at concentrations greater than 0.1 µg l⁻¹ in four of the analyzed compounds. Potential pollution of groundwater was conditioned by the spatial variability of geomorphological features, and influenced by others variables such as the intensity of herbicides use and the physicochemical properties of the compounds. In the present study, groundwater pollution is in line with the DRASTIC maps.