Abstract:
The atmospheric precipitation is an important phenomenon in which pollutants are scavenged
from the atmosphere. Wet deposition accounts for rain, fog and snow, while dry deposition is
the accumulation and fallout of aerosol particles and gases without dissolution of water. It is
very important to have baseline data on the chemical composition of the atmosphere to take
regulatory measures to control atmospheric pollution in Sri Lanka. The main objective of
this study was thus to determine selected trace metals (Al, Fe, Mn, Cu, Zn, Pb) in bulk
precipitation samples collected weekly in three sampling locations, namely the University of
Peradeniya premises, Polgolla and Kandy for a period of one year from August 2013 to July
2014. Trace metals were determined in filtered and preserved rainwater (bulk) samples using
Graphite Furnace Atomic Absorption Spectrometer, and volume weighted mean values of
selected trace metals were subsequently calculated. Kandy municipality showed the highest
contamination and followed the sequence of Al > Zn > Fe > Mn > Cu > Pb and volume
weighted mean concentrations of above sequence are 53.6 μg L-1, 38.0 μg L-1, 5.8 μg L-1, 5.4
μg L-1, 4.2 μg L-1, <2.0 μg L-1. Polgolla dam site also recorded some trace metal
contamination following the sequence, Al > Zn > Fe > Cu > Mn > Pb and volume weighted
mean concentrations of above sequence are 51.5 μg L-1, 40.5 μg L-1, 4.8 μg L-1, 2.4 μg L-1,
1.5 μg L-1, <2.0 μg L-1. Despite less industrialization and less traffic congestion, Peradeniya
University premises also showed some extent of atmospheric trace metal contamination
following sequence of Al > Zn > Cu > Fe > Mn > Pb and volume weighted mean
concentrations of above sequence are 46.1 μg L-1, 44.3 μg L-1, 2.6 μg L-1, 1.9 μg L-1, 1.7 μg
L-1, <2.0 μg L-1. Principal component analysis (PCA), used to predict possible sources for the
above trace metal contaminants, indicates that Mn, Cu and Zn are originated mainly from
anthropogenic activities, such as fossil fuel combustion and burning municipal waste. Al and
Fe are mainly originated from natural sources as those metals are the major components of
alumino-silicate based earth crust.
