Determination of Air Quality Through Analysis of Rainwater in Selected Geographical Areas in Kandy and Kurunegala Districts

Abstract

Dissolution of environmental pollutants, which are released mainly by anthropogenic sources, would alter the chemistry of rainwater, which affects ecosystems including humans. As industrial activated are steadily increased over time, the chemistry of rainwater is continuously changing. As such, it is of vital importance to monitor the rainwater quality to understand the levels of rainwater quality and to predict future risks so that protective measures could be taken. In this context, the study reported was aimed to investigate the chemical characteristics of bulk precipitation in selected areas in Kandy and Kurunegala districts representing urban and semiurban areas, namely, Kandy city, University of Peradeniya (UOP) and a suburb area of Kurunegala (Mallawapitiya) over a period of six months from May 2023 to November 2023, collecting samples on a weekly basis. A total of 75 samples analyzed for rainwater quality parameters using standard procedures revealed that the Kandy, UOP and Kurunegala sites had 32%, 20% and 28% dry-only precipitation events, respectively. A few acidic precipitation events (12%) were recorded in Kandy, and no acidic precipitation was recorded at the sites of the UOP and Kurunegala. The volume weighted mean (VWM) total hardness of the three sites were 5.91 mg CaCO₃ L^− 1 (Kandy), 3.90 mg CaCO₃ L^− 1 (UOP), and 4.54 mg CaCO₃ L^− 1 (Kurunegala), respectively, revealing that rainwater of all sampling sites was soft. The VWM concentration of major anions of the Kandy site was in the order of SO₄²⁻ < NO₃⁻ < Cl⁻ while the other two sites had the order NO₃⁻ < SO₄²⁻ < Cl⁻. The VWM concentrations of trace metals varied in the order of Pb < Cu < Mn < Fe < Zn < Al in both Kandy and UOP sites while in Kurunegala they varied as Pb < Mn < Cu < Fe < Zn < Al. Pearson correlation analysis showed that all three sites exhibit a very strong positive correlation between conductivity and salinity and a very strong to strong correlation between [Cl⁻] – [SO₄ ²⁻], [Cl⁻] – rainfall, and [Al] – [Fe]. Probable sources of these pollutants are vehicular emissions, crustal origin, biomass burning, industries, and agricultural activities.