Authors
Rongshuang Xu, Jiahui Shen, Yu-Chi Lin, Yuxiao Yang, Mei-Yi Fan, Yuan Dai, Yan-Lin Zhang
Published in
Environmental science & technology. Sep 16, 2026. Epub Sep 16, 2026.
Abstract
Despite stringent SO2 emission reductions, particulate sulfate (SO42-) concentrations often exhibit a nonlinear response. To reconcile this discrepancy, this study utilized synchronous sulfur isotope (δ34S) observations of precursor SO2 and product sulfate in Nanjing across a decade (winter 2015 vs 2024). Sulfate reductions are observed to lag behind SO2, declining together with elevated δ34S values in ambient sulfate (5.7 ± 1.1‰ vs 6.2 ± 1.3‰) and significantly in SO2 (1.4 ± 1.2‰ vs 6.5 ± 1.6‰), which indicates a shift in emission structure and sulfate formation chemistry. Unexpectedly, while SO2 source apportionment demonstrates a significant decline in contribution of coal combustion to regional SO2 emissions, coal combustion remains the predominant contributor to secondary sulfate, maintaining a stable relative share. This discrepancy implies enhanced conversion efficiency for coal-emitted SO2. We attribute this to the increased contribution of co-emitted transition metal ion (TMI)-catalyzed oxidation (rising from 35.6% to 59.0%), with kinetic calculations underscoring the dominance of the Mn-surface catalysis pathway. Ultimately, these findings suggest that intensified TMI-catalyzed oxidation sustains high sulfate production from coal-emitted SO2 even under low-SO2 conditions, providing a mechanistic explanation for the nonlinear response. These results also highlight the necessity for synergistic co-control strategies within coal-dependent industries.
PMID:
42758854
Bibliographic data and abstract were imported from PubMed on 19 Sep 2026.
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