Distribution of trace elements in the groundwater of the Escobar County, Buenos Aires, Argentina

Abstract

In the lower basins of the Luján, Escobar and Garín rivers, Escobar County, Province of Buenos Aires, Argentina, a regional pollution study was carried out in order to determinate the chemical and biological groundwater affectations, including natural and human factors. Hydrochemistry included well data, well samples, surface water samples, pollution sources and pollution indicators. A GIS was developed including a base map, georeferenced data and associated databases. The preparation and use of thematic cartography was used to analyse relationships. We analysed and detected groundwater contamination in areas with different land use. Water and soil samples were analyzed by multivariate methods so as to evaluate the relationship between trace elements and land use. In the Epiparaneana section we found the following concentrations: Cr between 0.6 and 50 μg/L, Cd between 3 and 18 μg/L, Cu between 4 and 160 μg/L, Fe between 0.11 and 177 μg/L, Mn between 0.03 and 1.44 mg/L, As between 0.002 and 0.041 mg/L, and F between 0.1 and 1.5 mg/L. Zn concentration was between 200 and 800 μg/L in the Pampeano aquifer, and between 20 and 160 μg/L in the Puelches aquifer. D and ¹⁸O isotopes were similar in vertical and horizontal distribution, establishing a hydrodynamic relationship between Epipuelches-Puelches section. The values showed a vertical decrease with depth. The natural association between F and As was related to the Pampeano silts. We found a significant correlation between nitrates and total coliformes (r = 0.85) related to urban use without sanitation services. Fe, Mn, Cu, Zn were related to intensive agricultural use, while Pb, Co, Ni and Cr showed a strong relation to industrial land use. Thematic maps showed a clear overlapping within areas of different association trace and land uses.