Water quality and construction aspects of the wells in the Jaguaribe River alluvial aquifer, Municipality of São João do Jaguaribe, Ceará

Abstract

This article discusses the constructive aspects of the wells and the physicochemical quality of groundwater in the Sedimentary Hydrogeological Domain scenario of the alluvial aquifer of the Lower Jaguaribe River Valley, São João do Jaguaribe, Ceará, in relation to land use and occupation. A significant portion of the mapped wells exhibits deficiencies in terms of construction aspects and sanitary protection recommended by ABNT. Regarding the quality of groundwater, physical-chemical analyses were carried out on 30 samples, determining parameters such as pH, turbidity, electrical conductivity, major cations and anions, total dissolved solids, silica, hardness, alkalinity, nitrogenous compounds, fluoride, iron, aluminum, and phosphate. The concentrations of nitrogenous compounds in the waters of the alluvial aquifer do not suggest significant local anthropogenic contamination, as nitrite and ammonia were rarely detected, and nitrate showed trace concentrations. The primary natural factor affecting water quality is the high concentration of iron, which is reflected in the turbidity and color of the water in almost all wells. Sodium and chloride levels in 37% of the samples characterize brackish water, while the remaining samples have total dissolved solids concentrations of less than 1000 mg L^-1. Therefore, in the study area, fresh water that requires iron removal treatment may become suitable for various uses. pH, ammonia, nitrite, nitrate, sulfate, and aluminum levels all fall within the maximum allowable values. The primary geochemical process affecting water quality is the rock-water interaction due to the long residence time of water in the alluvial aquifer, which, on average, considering the historical series (1973–2020), does not receive rainfall recharge.