SAMPLING OF AGROCHEMICALS FOR ENVIRONMENTAL ASSESSMENT IN RICE PADDIES - DRY TROPICAL WETLANDS, COSTA-RICA

This paper presents results from a preliminary sampling strategy devel oped to track agricultural contaminants found in surface and subsurfac e media and used commonly in rice paddy cultivation in the dry, tropic al forest coastal region of Guanacaste, Costa Rica. The emphasis is on the impact of eight indicator pesticides, five forms of nitrogen and phosphorus that are common nutrients found in fertilizers. After the f ield sampling strategy was developed, soil and water samples were coll ected twice: once during the beginning of the wet season and once duri ng the initiation of the dry season. Hydrological parameters, soil cla ssifications, agricultural product toxicology, irrigation and drainage networks, cultivated areas, land ownership, and pristine environments have been studied, mapped, and entered into a database in order to un derstand the spatial and temporal distribution of potential contaminan ts and their pending ecological degradation. Alternative crops and agr icultural practices are suggested to reduce or eliminate impacts on bi ological preserves; Data-base development and basin characteristics ha ve been entered into a Geographic Information System (GIS) that is cap able of fully integrating suggested site modeling. Field sampling resu lts indicate that proposed rice paddy cultivation in a relatively undi sturbed basin is likely to have minimal impact on downstream biologica l preserves.