Spatio-temporal Study of Pollutants in the Rio De Ondas Hydrographic Basin, West of Bahia, Brazil Using Multivariate Analysis

Abstract

Water bodies are containers that receive a large load of pollutants through the release of domestic, industrial, and agricultural effluents. With this focus, this work aimed to conduct a temporal-spatial variability study in the Rio de Ondas Hydrographic Basin through multivariate statistical analysis. For this, seventeen collection sites were established in four stations along the Rio de Ondas and its tributaries between 2017 and 2018. Ionic chromatography with suppressed conductivity was used for ions determination, while ICP-OES determined metals' total concentrations. The land use and occupation assessment between 1985 and 2015 was conducted using images from Landsat 5 and 8 satellites and the descriptive and multivariate analysis of the data using version 10 of the Statistica software. The results showed that, in thirty years, there was a growth of 569% of agricultural activities in the watershed area, with significant suppression of native vegetation, favoring the transport of pollutants to rivers. Ca2+, PO42−, Al, Cu, and Zn concentrations showed a statistically significant difference between the seasons, with higher medians in the rainy season. Rainy season influenced the formation of three groups in the PCA, consisting of electrical conductivity, salinity, TDS, and PO42− (group 1); temperature, Fe, SO42− and Cl− (group 2); and Ca2+, Mg2+, Na+, and HCO3− (group 3). The strong correlation between parameters of each group indicates anthropic influence on the watershed's water quality. However, levels are within the potability standard.