Abstract

RICALDI, E.. POLLUTION HALOS IN THE SUB WATERSHED OF THE ANTEQUERA RIVER (PAZÑA, DEPARTMENT OF ORURO). Revista Boliviana de Física [online]. 2009, vol.15, n.15, pp.22-31. ISSN 1562-3823.

Vertical electrical sounding measurements (VES) were taken at the sub watershed of the Antequera River located within the Pazña Municipality in the Department of Oruro. The results were used to study the environmental contamination problems caused by mining activity in the area. Seven profiles were obtained using measurements taken at different longitudes, from the most extensive at Avicaya to the confluence of the area's rivers at 2,800 and 1,800 metres respectively. Surface area data was used to form a preliminary definition of the "polution halos" in two dimensions (maps). The curves of the electrical resistance soundings were converted to a three layer model that enables a preliminary discussion of the "pollution plumes" in three dimensions, i.e., the volume of subterranean pollution. Data and results were correlated with exact electrical conductivity measurements, pH values, and results from a chemical analysis of soil and water taken by a group of hydro-chemical researchers and complemented by visual observations of the state of the ground in situ. A first analysis and interpretation of the results indicates that approximately 60% of the lands in the central longitudinal zone of the planes of the sub watershed of the Antequera River are contaminated. The contaminated areas are distributed between high and low gradient areas in the north water bodies are affected by acidity produced through mining activity. In the south, water quality is affected by the alkaline properties of thermal waters. A percentage of 40% of the sub watershed, especially in the west and surroundings, remains free of contamination (we believe that it must be preserved). Greater detail is shown in the environmental risk map produced as part of the study.

Keywords : geoelectricity; electromagnetic induction and conductivity; environmental studies.

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