Nitrate temporal and spatial patterns in 12 water-supply wells, Yucatan, Mexico

The nitrate concentration in 12 water-supply wells were monitored for the p eriod April 1992 to March 1993. Each water-supply well was sampled once a m onth. The nitrate concentrations in the 12 wells ranged from 7 to 156 mg/l. Two water-supply wells (Chacsinkin and Peto) showed concentrations that re ached 3.5 times the maximum permissible limit for the Drinking Water Standa rd (45 mg/l). A third water-supply well (Akil) exceeds the norm for 7 out o f 12 months. The use of nitrogen-rich fertilizers are responsible for high nitrate concentrations in groundwater in the southern part of Yucatan, Mexi co where intensive agricultural practices exist.