Electrical resistivity tomography applied to detect contamination on a dairy farm in the Pampean region,Argentina

摘要

On dairy farms, it is important to identify the degree of contamination that different management units, as localized sources, produce on soil and groundwater due to animal effluents. This information may be used to improve management practices in order to maintain not only environmental sustainability but also the standards of milk production. The aim was to test the performance of electrical resistivity tomography to detect anomalies of resistivity and to identify the relative impact,on physicochemical properties of soil and groundwater, produced by the effluents of the different management units of a dairy farm situated in the southern part of Santa Fe Province (Argentina).Twelve electrical resistivity tomography (ERT) profiles were carried out and 2D models of the resistivity distribution were interpreted together with the physicochemical analysis of soil and groundwater samples. At the plots around the milking house, resistivity decreased in the non-saturated zone between 60-84% relative to the background values, being the maximum value for the feeding zone, the most critical management unit, in agreement with sampling results. The surroundings of the lagoon of effluents showed a decrease of resistivity around 80%, even on the phreatic aquifer, due to flooding events in the past. Electrical resistivity tomography was sensitive enough to evaluate anomalies in the distribution of electrical conductivity associated with an increase of nitrates, sulphates and bicarbonates, in addition to phosphorous in soil and chlorides in groundwater,in all cases probably connected directly or indirectly with the animal waste.