An investigation of inorganic nitrogen compounds in the groundwater in the Valley of Mexico

Abstract

Contaminated surface water and well water from various locations in the valley were sampled and analysed for geochemical and environmental isotope parameters. The results were compared in an attempt to identify the presence of the surface water in the well water. Unfortunately the characteristics of the surface water were generally not different enough from the well water to determine if widespread anthropogenic contamination was occurring. Anthropogenic contamination in recharge areas appears to be indicated by elevated nitrate concentrations in these areas. Anthropogenic contamination in the southern part of the valley was demonstrated by high ammonium concentrations and the presence of faecal coliforms in the groundwater. Although wells completed below the clay in the central part of the valley do not appear to be contaminated, we should not assume that the clay is impermeable and therefore offers complete protection from surface sources of contamination. -from Author