CHEMICAL COMPOSITION AND SOURCES ATTRIBUTION OF RAINWATER IN BANDUNG AREA, INDONESIA

Data of international and national monitoring stations have showed evidences of rainwater acidification in Indonesia. This research aimed to investigate the small-scale variations and the influence of urban activities to rainwater chemical composition in Bandung, Indonesia, as well as to determine the contributing sources to its chemical variation. Rainwater bulk samples had been collected weekly at 4 (four) locations representing differences in altitude and local land use, from February to September 2016. Samples were analyzed for pH, conductivity, and major ions (SO4, NO3, Cl-, Na+, Ca2+, Mg2+, K+, and NH4). The results showed that the pH of rainwater were in the range of acidic to normal (average 5.42 ± 0.72), where ammonium acted as the major neutralizing factor (NF). Small-scale spatial variability of nss-SO4, NO3, nss-Cl-, nss-Ca2+, nss-Mg2+, and NH4 within 4 (four) locations were observed. Sulphate and NO3 as well as Ca2+ and Mg2+ were significantly correlated, with r = 0.870 and r = 0.929, respectively. Principal Component Analysis (PCA) indicated three main sources of rainwater chemistry. Firstly, a mix of natural sources (e.g., sea-salt aerosols, crustal elements and waste decomposition) which consisted of sea-salt SO4, ss-Cl-, Na+, ss-Ca2+, nss-Ca2+, ss-K+, nss-K+ and NH4. Secondly, fossil fuel combustion/vehicular emissions, which consisted of nss-SO4, NO3, H+, and nss-Mg2+; and thirdly, nss-Cl + presumably from other acid reaction. These three components accounted for 80.25% of the total variance. The results suggested that local and long-range transported emissions of natural and anthropogenic sources contributed to the rainwater chemistry in the Bandung area.