Land use and the distribution of nitrate concentrations in the urban aquifer of the Bauru City, SP

Abstract

This work analyzed nitrate contamination in the Bauru Aquifer System (BAS) in the urban area of the municipality of the same name and related its occurrence with urbanization. The methodology used included: i) record and treatment of hydrochemical data from 634 drilling wells; ii) survey of the evolution of sewage network from 1976 to 2022; iii) analysis of land use and occupation; and iv) evaluation of the nitrate concentrations between 1999 and 2022. The seasonal evaluation of recent nitrate concentrations in 151 groundwater samples from 76 selected drilling wells allowed identifying concentrations up to 23 mg/L N-NO₃^-, whose values are mainly distributed in the central region of the urban area, occupied between 1910 and 1980, with older sewage system (before 1976), and urban occupation density, from medium to high. An increase trend in median nitrate concentration (Md) values was observed, from 0.20 to 3.29 mg/L N-NO₃^-. The statistical analysis between nitrate concentrations, the ages of the urban area and the sewage network, the urban occupancy density, and well depth showed that the urbanization and sanitation affect the presence of this contaminant in the aquifer.