Changes in source contributions to the oxidative potential of PM2.5 in urban Xiamen, China

• Published in: Journal of environmental sciences (China) 2025-03, Vol.149, p.342-357
• Main Authors: Li, Jia-Min, Zhao, Si-Min, Miao, Qi-Yu, Wu, Shui-Ping, Zhang, Jie, Schwab, James J.
• Format: Article
• Language: English
• Subjects: Chemical composition; Interannual change; Oxidative potential; PMF-MLR; Source apportionment
• ISSN: 1001-0742
• DOI: 10.1016/j.jes.2024.02.003

•Water-soluble metal ions were the dominant contributors to the DTT activity in PM2.5.•Organics contributed more to DTT activity in 2022 than in 2017/2018.•PM2.5 showed a lower exposure risk and higher intrinsic oxidative toxicity in 2022.•The relative contributions of vehicle emissions, coal/biomass burning, and ship emissions to DTT activity decreased dramatically in 2022. The toxicity of PM2.5 does not necessarily change synchronously with its mass concentration. In this study, the chemical composition (carbonaceous species, water-soluble ions, and metals) and oxidative potential (dithiothreitol assay, DTT) of PM2.5 were investigated in 2017/2018 and 2022 in Xiamen, China. The decrease rate of volume-normalized DTT (DTTv) (38%) was lower than that of PM2.5 (55%) between the two sampling periods. However, the mass-normalized DTT (DTTm) increased by 44%. Clear seasonal patterns with higher levels in winter were found for PM2.5, most chemical constituents and DTTv but not for DTTm. The large decrease in DTT activity (84%−92%) after the addition of EDTA suggested that water-soluble metals were the main contributors to DTT in Xiamen. The increased gap between the reconstructed and measured DTTv and the stronger correlations between the reconstructed/measured DTT ratio and carbonaceous species in 2022 were observed. The decrease rates of the hazard index (32.5%) and lifetime cancer risk (9.1%) differed from those of PM2.5 and DTTv due to their different main contributors. The PMF-MLR model showed that the contributions (nmol/(min·m3)) of vehicle emission, coal + biomass burning, ship emission and secondary aerosol to DTTv in 2022 decreased by 63.0%, 65.2%, 66.5%, and 22.2%, respectively, compared to those in 2017/2018, which was consistent with the emission reduction of vehicle exhaust and coal consumption, the adoption of low-sulfur fuel oil used on board ships and the reduced production of WSOC. However, the contributions of dust + sea salt and industrial emission increased. The change trends of PM2.5, DTT activity, non-cancer and cancer risks due to the selected elements (V, Cr(VI), Mn, Ni, As, Se, Cd, Ba, Pb, Mo, Sb, and Co) [Display omitted]