Principal Component Analysis of Seasonal Trends in Groundwater Contamination around the Abule-Egba Dumpsite, Lagos, Nigeria

Abstract

This study assessed seasonal variations in groundwater contamination around the Abule-Egba dumpsite in Lagos, Nigeria, using Principal Component Analysis (PCA). Groundwater samples were collected from five boreholes and one leachate spring during both the wet and dry seasons. Physicochemical parameters, including pH, temperature, electrical conductivity, total dissolved solids, turbidity, and major ions (e.g., NO₂⁻, SO₄²⁻, Cl⁻, Ca²⁺, Mg²⁺), as well as heavy metals such as Pb, Cd, Cr, and Fe, were analyzed. The PCA revealed distinct seasonal patterns in contaminant distribution. During the wet season, the first three principal components explained approximately 80.84% of the total variation in groundwater quality data. In contrast, the dry season showed an even stronger pattern, with the first three components accounting for over 92% of the variance, PC1 alone contributing 66.16%. PC1 was influenced heavily by parameters linked to natural geochemical interactions, leachate infiltration, and human activities. The concentrations of nitrates and heavy metals recorded were observed to be higher during the wet season. The findings show that the Abule-Egba dumpsite has a significant impact on the groundwater quality within the vicinity of the dumpsite, as several locations had contaminant levels exceeding the limit set by the World Health Organization and the Nigerian Standard of Drinking Water Quality.