Supporting Data for “Riverine modulation of volatile sulfur compound distributions: A case study in the Bohai and Yellow Seas”

Volatile sulfur compounds (VSCs), including dimethyl sulfide (DMS), carbonyl sulfide (COS), and carbon disulfide (CS2), play key roles in atmospheric chemistry and climate regulation Although riverine inputs theoretically promote VSCs production by supplying nutrients and chromophoric dissolved organic matter (CDOM), unexpectedly low VSCs concentrations are frequently observed in estuarine waters, suggesting the presence of additional limiting factors that remain poorly understood. In this study, concentrations of DMS, COS, and CS2 were quantified in surface waters, vertical profiles, and the overlying atmosphere of the Bohai and Yellow Seas during spring and summer 2024. Average surface concentrations of DMS, COS, and CS2 were 6.3, 0.11, and 0.09 nmol L-1 in spring, increasing to 9.7, 0.35, and 0.19 nmol L-1 in summer. DMS showed strong positive correlation with chlorophyll-a, while COS correlated with CDOM. Riverine inputs of nutrients and CDOM from the Yellow River enhanced VSCs production, although elevated turbidity limited light availability and thus suppressed biological and photochemical pathways. Atmospheric mixing ratios in spring averaged 61.1, 408.7, and 105.5 pptv for DMS, COS, and CS2, respectively. Sea-to-air flux measurements demonstrated that DMS was the dominant contributor to atmospheric sulfur in the study region, with fluxes of 5.4 µmol m-2 d-1 in spring and increasing to 15.0 µmol m-2 d-1 in summer. By contrast, COS and CS2 contributed smaller but non-negligible sulfur fluxes in spring, averaging 0.6 and 0.4 µmol m-2 d-1, respectively. The results underscore the role of coastal marginal seas as active sources of atmospheric VSCs and highlight the critical influence of riverine input in sharping the production and emission of VSCs in coastal region.