Abstract

MORALES VARGAS, Ricardo. Risk analysis methodology for agrochemical contamination: San Blasriver basin, Costa Rica. Rev. costarric. salud pública [online]. 2013, vol.22, n.1, pp.34-44. ISSN 1409-1429.

Objective: To establishsoil and hydrogeological parameters for the basin; as well as fertilizer and pesticide physical and chemical parameters that could be used to analyze their risk of percolation. Materials and methods: A field and literature survey was conducted to characterize the basin from a hydrogeological standpoint. The concentration of nitrates and pesticides in ground water and surface water was analyzed. Some of the intrinsic vulnerability characteristics of the aquifer were considered, in particular those related to adsorption and retention of contaminants and those related to chemical characteristics of the soil. The distribution coefficient and retardation value were determined for six agrochemicals of high use in the basin, in order to establish their relative risk to groundwater. The Pearson correlation coefficient was calculated for nitrate concentration in groundwater and the diverse soil parameters considered. Results: Groundwater in agricultural are as has two to three times the nitrate concentration relative to that of groundwater in wells for human consumption. Glyphosate was foundin agricultural irrigation canals. The soil chemical parameters morestrongly related to contaminant (nitrates)inground water were: a) cation exchange capacity, b) aluminum/silicon ratio,c) % soil nitrate retention, and d) soil pH using distilled water.The sum of fines (% clay + % silt) was found to directly relate to groundwater nitrate concentration. Discussion: Parameters are proposed for risk analysis in alluvial aquifers in the Pacific coast of Costa Rica, where agricultural use is predominant. Terbutylazine, ametryn, carbendazim, diuronand nitrates representan important threat to the aquifer.

Keywords : aquifer; risk; vulnerability; pesticides; nitrates; Costa Rica.

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