FAST TRANSMISSION OF NITRATES INTO A DETRITIC AQUIFER (LEPE, HUELVA, SPAIN)

The nitrate ion has become in recent years extremely prevalent, particularly in the uncarbonated coastal aquifers. This is due to its almost exclusive origin in contamination from agricultural activities, which are especially intense in these aquifers. This article describes a study of the causes of fast mobilization of nitrates and their almost instant (though very localized) transmission to detritic coastal aquifer, increasing sharply their percentage in the groundwater and making it undrinkable. The nitrates originate from solid and liquid nitrogenous fertilizers which are used as manure in the growing of strawberries and citrus fruits by the farmers of the region. The high amount of fertilizers used, the proximity of many crops to the groundwater wells for urban supply the unsuitable construction of certain wells, and a period of very intense precipitation during November and December in 1989 can be considered among the principal causes of the high content of nitrates in the groundwater in some locations which has obliged the Town Hall of Lepe to declare the water undrinkable for 3 1/2 months.