Cropping and livestock impacts on surface waters in the Pampas region (Argentina)

Abstract

The rivers and streams of the cropping and livestock regions of Buenos Aires province (Argentina) contain variable concentrations of pollutants and high concentrations of nutrients that simultaneously affect aquatic ecosystem communities. In the present study, we evaluated the water quality of the Burgos stream and El Tala river (San Pedro, Buenos Aires province) by analyzing chemical contaminants (As, Cu, Pb, Zn, and glyphosate), nutrients (ammonium, nitrate, and phosphate), and algal toxicity bioassays. Surface water was collected at six sampling stations in three months (April and September 2019, and February 2020). By taking into account the percentages of algal growth inhibition (%I), the standard species Raphidocelis subcapitata and a species isolated from the study area, Scendesmus acutus, showed different sensitivities to the water samples, with a maximum %I of 70.64% and 34.62%, respectively. Moreover, algal growth stimulation was observed due to the high nutrient concentrations. A risk quotient (RQ) was applied to evaluate the environmental hazards of the chemical contaminants Cu, Pb, Zn, and glyphosate on the algal populations. According to the RQ values obtained for Pb (1.20 and 3.30) and Zn (1.17 and 2.12), the growth of algal populations could be at risk due to the maximum environmental concentrations measured of Pb (132 µg L-1) and Zn 106 µg L-1). The present study showed the first approach of an environmental risk analysis based on simultaneous determinations of chemical contaminants and laboratory bioassays with algae, using a strain of alga isolated from the aquatic ecosystems studied.