Trace Metal Composition of Bulk Precipitation in Selected Locations of Kandy District, Sri Lanka

Abstract

Atmospheric precipitation in Sri Lanka occurs mainly through rain whose terrestrial composition significantly varies based on the location as the regional geography and anthropogenic factors can largely affect environmental pollutants that are added to the atmosphere. It is therefore very important to have baseline data on the chemical composition of the atmosphere to take regulatory measures to control atmospheric pollution although very limited data available in Sri Lanka. The main objective of this study was thus to quantitatively determine selected trace metals (Al, Cr, Cu, Fe, Mn, Pb, and Zn) in bulk precipitation samples collected weekly in three sampling locations, namely the University of Peradeniya (UoP), Polgolla, and Kandy City Central (KCC), for a period of 1 year from March 2018 to March 2019. Trace metals determined using atomic emission spectrophotometry indicated that the KCC site showed the highest contamination following the sequence (with respective volume-weighted mean (VWM) concentration values) of Al (79.7 μg L−1) > Fe (42.8 μg L−1) > Zn (39.3 μg L−1) > Mn (13.9 μg L−1) > Cu (9.8 μg L−1) > Cr (2.4 μg L−1). The corresponding values of the Polgolla site showed the sequence Zn (64.3 μg L−1) > Al (52.1 μg L−1) > Fe (17.9 μg L−1) > Mn (11.1 μg L−1) > Cu (5.4 μg L−1) > Cr (1.8 μg L−1). Due to less industrialization and less traffic congestion, the UoP site showed low trace metal levels in the order Zn (29.8 μg L−1) > Al (21.3 μg L−1) > Fe (14.2 μg L−1) > Cu (7.4 μg L−1) > Mn (4.3 μg L−1) > Cr (0.9 μg L−1). Principal component analysis indicated that Cu, Mn, and Zn originated mainly from anthropogenic activities, such as combustion of fossil fuel and burning of municipal waste, while Al and Fe mainly originated from natural sources.