A thesis submitted in partial fulfillment for the requirements of the degree of Master of Science, School of Engineering and Technology

Thesis (M.Sc.) - Asian Institute of Technology, 2001

Four sites representing different land-use were selected in this study. Data records were 475 rain events from 1992 to June 2000. The sampling only used for rain events of larger than 2 mm. Average samples were collected for one week interval. Concentration of major ions (H+, Na+, so/·, N03- and Cl") was used for analysis. Concentration of nssso/· was calculated. The acidified events were about 8.3 %. The seasonal loads of these ions were calculated. The study showed the seasonal cycles clear of nss-So/·. The temporal trends of these ion concentrations were very similar at all sites and showed a consistent increase in late winter. Conversely, they descended in late summer when the precipitation showed higher amount. At all sites, the frequencies of acidified events depended on the weather conditions such as intensity, rainfall and wind velocity. These frequencies were also varied by wind direction in no1th and south. Data reduction was used to classify the parameters into four factors. The first factor was ion concentration that was coming from sea salt. The second factor was ion concentration that was coming from emission sources. The third factor was the weather condition including amount, intensity of rainfall and wind speed. The last factor was wind direction index. The regressions of major anions were presented.