Pollution by nitrate in the urban and rural zone of Macachín’s town, La Pampa, Argentina

Abstract

The town of Macachín is located over the Valle Argentino aquifer. There, the phreatic aquifer is lodged in a sandy superficial cap and in the slime-sandy sediments. The objective of this work is to depict the pollution of the unconfined aquifer of Macachín, considering the presence of nitrate as determining factor of the quality of the resource. The periurban area was analysed with the purpose of cover the area of relocalization of the sources of potable water for the town. In the urban area, the domiciliary perforations and in those of supply were considered. Samples in perforations and in drilled wells were collected. Temperature, pH, electrical conductivity and the ions concentration for nitrate, nitrite and chloride were measured. Statistical basic parameters were calculated for eight wells in exploitation and also for the perforations and drilled wells. It was concluded that the conditions of the underground waters is little satisfactory. All of the domiciliary wells sampled contained a quantity of nitrate that overcomes the maximum levels allowed for the consumption of potable water. In the city’s wells of supply a significant increase of the nitrate concentrations was identified since 1998, approximately. The contribution of organic matter to the underground water could be originated in the decomposition of the domiciliary wastes arranged in cesspools. In both areas, the nitrate concentrations in the unsaturated zone are similar and superior to the limit allowed for human consumption. The pollutant sources in the rural zone can be permanent corrals of animals.