Resumo

GIULIANO ALBO, María J  e  BLARASIN, Mónica T. Hidrogeoquímica y estimación del fondo natural de nitratos del agua subterránea en un agroecosistema del pedemonte de la sierra de Comechingones. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.3, pp.378-392. ISSN 0004-4822.

For many rural communities, groundwater is the only source for human consumption. A problem that changes groundwater chemistry is the occurrence of nitrates, an indicator of anthropogenic pollution. Nitrate sources are agricultural activities (use of agrochemicals and extensive or intensive livestock). Due to the potential impact of such activities, the objective of this study is to assess the hydrochemical characteristics of the unconfined aquifer in an agroecosystem and to estimate the characteristic natural background value (NBV), the natural background range (NBR) and anomalous nitrate values. All these issues were linked to hydrogeological characteristics and land uses. Nitrates values between 3.0 and 192.5 mg/L were detected in groundwater. The NBR was 3.0 to 10.1 mg/L and the NBV was 7.5 mg/L. From all the samples obtained, 65 % is above the maximum limit of NBR and 87.5 % exceeds the NBV. The anomalous NO3- values are associated with different pollution sources. The highest are related to punctual sources, mainly cow and pig feed-lots, whereas the lowest are linked to diffuse contamination sources like disperse animal farming and fertilizers (urea, ammonium phosphate and sulfate) for soybean and maize crop.

Palavras-chave : Nitrates; Anomalies; Geochemistry; Agricultural ecosystem; Unconfined aquifer.

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