Rainwater Composition and Acidity at Five Sites in Malaysia, in 1996

Rainwater chemical composition and acidity were determinedfrom weekly-averaged wet-only rainwater samples collected atfive sites in Malaysia throughout 1996. The major aim of thiswork was to assess the extent to which acid deposition, foundpreviously at one site in the Klang Valley, was a general,rather than local, phenomenon. To this end, three measurementsites were located spanning the length of the Klang Valley (anurban-industrial region of approximately 3000 km2containing the Malaysian capital, Kuala Lumpur). A fourth sitewas located outside, but adjacent to the Klang Valley, and thefinal site was located 300 km to the southeast, in anurban/industrial region adjacent to Singapore. Annual pHvalues in the range 4.16–4.40 and estimated total depositionfluxes of acidic sulfur and nitrogen species in the range 120–350 meq m-2 yr-1 show all sites to be impactedsignificantly by acidic deposition. Average contributionswere 60% as sulfur species, 40% as nitrogen species. Theresults confirm that potentially significant levels of aciddeposition occur in Malaysia as a regional phenomenonassociated with urban/industrial activities.