Urbanization and initial groundwater quality investigation in Malabe, Sri Lanka

Malabe, an eastern suburb of the capital city of Colombo, is one of the most rapidly urbanized and industrialized areas in Sri Lanka. Groundwater is a valuable resource in Malabe and it is being polluted. Malabe is located in a wet climatic zone with a lateritic aquifer that normally contains water with a very low pH that can cause quality problems. Our objective was to investigate and analyze the Malabe groundwater quality to understand the characteristics of significant parameters and their correlation so that policy planning can be correctly done. Groundwater samples from 16 water wells were collected and evaluated for eight physicochemical parameters, i.e., pH, turbidity, electrical conductivity (EC), color, nitrate (NO₃), nitrite (NO₂), sulfate (SO₄), and phosphate (PO₄). Two biological parameters were also determined for four wells. The essence of this finding is that the groundwater is very acidic, has a very low EC, but high coliform counts. Multivariable statistics of the data were performed using Pearson’s correlation and principal components analysis (PCA) using the Princom package in the R statistical package. The first four principal components (PCs) explained 79.8 % of the total observed variance in the data. The most significant parameters from the first principal component, PC1, were the positive correlations of turbidity and PO₄, and negative correlations of EC and NO₃A significant positive loading of pH with a negative loading of SO₄ was illustrated in PC2. These findings were similar to the correlation results. We concludes that the high acidity of the groundwater is primarily caused by industrial waste. The groundwater pollution of the Malabe area was not cause by inorganic fertilizer but by anthropogenic waste runoff. Our finding is crucial for groundwater quality management in the study area.