The results of chemical analyses of precipitation samples collected in Sing
apore between August 1997 and July 1998 are presented. Major inorganic and
organic ions were determined. in 169 rain samples collected using an automa
ted wet-only sampler. The daily sample pH values ranged from 3.49 to 6.54 w
ith a volume-weighted mean of 4.50, and about 88% of the samples had pH val
ues less than 5.0. Nss-SO42- 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 anal
ysis to find possible sources of the measured chemical species. Three compo
nents that accounted for 83.5% of the total variance were extracted: sea-sp
ray (Na+, Cl- and and Mg2+) and soil particles (Ca2+ and K+), acid factor (
nss-SO42-, NO3-, NH4+, and H+), and biomass burning (HCOO- and CH3COO-).