Spatiotemporal distribution in chemical composition of wet atmospheric deposition in Bandung Indonesia.

Abstract

Bandung, Indonesia, represents the complex interactions between climate variability, basin topography, and deposition processes. This study conducted a long-term spatiotemporal analysis, including pH distribution and pollutant accumulation monitoring, to observe the chemical composition of wet deposition in Bandung as part of the Acid Deposition Monitoring Network in East Asia (EANET). The results revealed that ${\text{NH}}_4^{+}$ and ${\text{NO}}_3^{-}$ were the predominant ions, followed by ${\text{SO}}_4^{2-}$ , with their distribution varying across different sites due to local emissions and atmospheric processes. The interactions between these ions, particularly the formation of secondary inorganic aerosols such as ammonium sulfate and ammonium nitrate, were closely linked to the basin's localized sources and topographical features. Areas experiencing high traffic congestion were classified as acidic regions due to their low pH levels. In contrast, a rural site exhibited a basic pH due to the high concentration of ion ${\text{NH}}_4^{+}$ . Variations in pH and conductivity, along with the impacts of climatic events such as El Niño and La Niña, emphasized the role of weather patterns in shaping wet deposition dynamics. Seasonal trends indicated elevated total ion concentrations during the dry season, driven by sea salt contributions, as supported by strong correlations between Na⁺ and ${\text{Cl}}^{-}$ and between Na⁺ and Mg²⁺. Additionally, geological materials and atmospheric reactions contributed to the strong correlations observed between soil-derived cations and acidic species. The increasing trend in ${\text{nss}-\text{SO}}_4^{2-}$ and the contrasting decrease in ${\text{NO}}_3^{-}$ concentrations in rural areas suggest evolving emission sources and environmental conditions.