Groundwater Contamination by Nitrates in the Yucatan Peninsula, Mexico
1997
Pacheco A., Julia | Cabrera S., Armando
Limestone is the main rock type that underlies the northern Yucatan Peninsula, and the region is therefore characterized by karstic features and high permeability and porosity. Rainfall infiltrates rapidly through fissures until it reaches the water table. No surface waters exist in the area, except in sinkholes and at the coastal margin, and the aquifer is the only source of water supply. The aquifer is also the only place where waste waters are discharged, thereby contributing to the most important water-quality problem of the entire Peninsula.For this study, approximately 380 water samples were analyzed for nitrate, using both the Brucine and the ultraviolet methods. These samples came from eight shallow wells in a rural part of the northern Peninsula and were collected during 1983–86. Nitrate concentrations in 56 percent of the analyzed samples were greater than 45 mg/L. These values exceed by several times the maximum permissible levels established by both Mexican and U.S. health agencies and are sufficient to cause methemoglobinemia in infants (blue baby syndrome). Nitrate concentrations vary seasonally and are generally greatest during the rainy season. Substantial differences in values of nitrate concentrations were observed in groundwater from adjacent wells, indicating local rather than regional contamination.
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