CHEMICAL COMPOSITION OF RAINWATER IN SINGAPORE

Abstract

The chemical composition of rainwater in Singapore was investigated from July to December 1997. Sampling was done on the rooftop of a building at the NUS campus using a wet only automated rainwater collector. Conductivity, pH, major anions and cations of the samples were determined. The ionic balance was calculated. It was found that more than 90% of the precipitation was acidic, with a mean pH of 4.56. The acidity was mainly due to H2SO4, HNO3 and HCl, and the major neutralising cations for these acids were Ca2+ and NH4+. The concentrations of most of the ions in rainwater were measured during the dry season (August-October 1997) and were influenced by biomass burning in Indonesia, which effected the regional air quality. The inter-element relationships among major anions and cations were examined.