Classificação da salinidade da água de poços com base na concentração de cloretos

Abstract

The scarcity of surface water resources is a recurring problem that affects the Brazilian semiarid. The waters found underground in the state of Ceará are a more viable alternative for human consumption. The crystalline formations that constitute the state's geology, however, tend to produce high salinity waters, with the chloride ion being one of the main causes of this salinity. The presence of chlorides in water results in its salty taste and the high salinity can be harmful to crops if the waters are used for irrigation. CONAMA’s Resolution No. 396/08 establishes the maximum value for the chloride content allowed in water for human consumption and CONAMA’s Resolution No. 357/05, classifies water bodies as to their salinity. Samples from 15 wells located in different regions of the state were analyzed at the Laboratório de Química Ambiental in NUTEC, under the parameters of chloride concentration and conductivity. The salinity of the samples was then calculated based on the chloride content. Most of the samples collected from wells in the central-west region showed chloride contents within the limits allowed by the legislation, being classified as fresh water. The samples taken in the northeastern region of the state and most of the samples from the central-north region had chloride levels higher than allowed and were classified as brackish waters, not being recommended for human consumption until they are subjected to adequate treatment.