Physical-chemical monitoring of water from the Areial-PB

Abstract

This study aimed to evaluate the water quality of the Areial Dam in Paraíba, Brazil, by monitoring physicochemical parameters at three distinct points and during three sampling periods, comparing the results with the limits established by CONAMA Resolution No. 357/2005 for freshwater and by GM/MS Ordinance No. 888/2021. Samples were collected manually in 5-liter PET bottles from the surface layer (≈20 cm) in the morning and transported under refrigeration (≈4 °C) to the laboratory. The analyses followed the methodologies of the Standard Methods for the Examination of Water and Wastewater (APHA, 2017) and included pH, turbidity, electrical conductivity, total dissolved solids (TDS), hardness, alkalinity, and chlorides, among other parameters. The results indicated that most variables remained within legal standards, with pH between 7.45 and 9.5 and low turbidity. However, a persistent increase in electrical conductivity (1940–2850 µS/cm), total dissolved solids (1079–1421 mg/L), and total hardness (up to 1000 ppm) values ​​was observed, characterizing very hard water with a tendency towards salinization. These results suggest a combined influence of natural factors, such as local geology and seasonal evaporation, and possible anthropogenic impacts, such as agricultural runoff. It is concluded that, although the water presents good overall quality according to legal standards, the observed salinization demands continuous monitoring and sustainable management strategies to prevent future compromise of the dam's water quality.