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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 NH 4 + and NO 3 - were the predominant ions, followed by 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 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 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 nss - SO 4 2 - and the contrasting decrease in NO 3 - concentrations in rural areas suggest evolving emission sources and environmental conditions. [ABSTRACT FROM AUTHOR]

Alkaline wastewater from tunnel construction can cause environmental problems when draining into water streams like rivers and lakes. Research interest in the neutralization of alkaline wastewater using CO 2 based on the carbon utilization concept has been increasing. In this study, the effects of key parameters such as the flow rate (FR) of CO 2 , initial water temperature (T), pH, and turbidity (TURB) on CO 2 neutralization of alkaline wastewater were investigated through laboratory experiments and field tests using alkaline wastewater collected from the Yunnan Dianzhong Water Diversion Engineering, China. Results revealed that 1.5 L min−1 was the optimal flow rate for CO 2 gas. The water pH (p < 0.001) and TURB (p < 0.001) significantly affected the neutralization performance of CO 2. The pH, TURB, electrical conductivity and total dissolved solids of alkaline wastewater can be effectively reduced by CO 2. The least time required for the treatment was noted at a T, pH, and TURB of 20 °C, 10.5, and 80 NTU, respectively. Laboratory and field stability experiments have shown CO 2 to be effective in reducing the pH of alkaline wastewater and consistently maintaining its pH within the discharge standard compliance range (6–9). A cost saving of $0.26 per 1 m3 of water was achieved comparing with neutralization of alkaline wastewater using citric acid. In summary, this study for the first time explored the efficiency and potential influencing factors for the treatment of alkaline tunnel construction wastewater using CO 2. It proves the effectiveness and economic benefits of the proposed technology. [Display omitted] • PH, turbidity, and CO 2 flow rate mainly affect CO 2 neutralization. • CO 2 neutralization reduces alkaline wastewater pH with good stability. • CO 2 neutralization is 92.86% less expensive compared with citric acid neutralization. • CO 2 neutralization enabled alkaline wastewater to meet the standard discharge (<9). [ABSTRACT FROM AUTHOR]