Chemical and Statistical Analysis of Precipitation in Singapore

The results of chemical analyses of precipitation samples collected in Singapore between August 1997 and July 1998 are presented. Major inorganic and organic ions were determined in 169 rain samples collected using an automated wet-only sampler. The daily sample pH values ranged from 3.49 to 6.54 with a volume-weighted mean of 4.50, and about 88% of the samples had pH values less than 5.0 Nss-SO₄ ^2? accounted for about 53 % of the sum of anions in rain, whereas chloride, nitrate, formate, and acetate accounted for the remainder. Rain chemistry data were analyzed using principal component analysis to find possible sources of the measured chemical species. Three components that accounted for 83.5% of the total variance were extracted: sea-spray (Na⁺, Cl^? and and Mg²⁺) and soil particles (Ca²⁺ and K⁺), acid factor (nss-SO₄ ^2?, NO₃ ^?, NH₄ ⁺, and H⁺), and biomass burning (HCOO^? and CH₃COOO^?).