Spatial and seasonal variability in volatile organic sulfur compounds in seawater and overlying atmosphere of the Bohai and Yellow Seas

Abstract. To better understand the production and loss processes of volatile organic sulfur compounds (VSCs) and their influence factors, VSCs including carbon disulfide (CS₂), dimethyl sulfide (DMS), and carbonyl sulfide (COS) were surveyed in the seawater and atmosphere of the Bohai and Yellow Seas during spring and summer of 2018. The concentration ranges of COS, DMS, and CS₂ in the surface seawater during spring were 0.14–0.42, 0.41–7.74, and 0.01–0.18 nmol L^-1, respectively, and 0.32–0.61, 1.31–18.12, and 0.01–0.65 nmol L^-1 during summer. COS and CS₂ had high concentrations in coastal waters, which may be due to elevated photochemical production rates. High DMS concentrations occurred near the Yellow River, Laizhou Bay, and Yangtze River Estuary coinciding with high nitrate and Chl a concentrations due to river discharge during summer. The depth distributions of COS, DMS, and CS₂ were characterized by high concentrations in the surface seawater that decreased with depth. The mixing ratios of COS, DMS, and CS₂ in the atmosphere were 255.9–620.2 pptv, 1.3–191.2 pptv, and 5.2–698.8 pptv during spring, and 394.6–850.1 pptv, 10.3–464.3 pptv, and 15.3–672.7 pptv in summer. The mean oceanic/atmospheric concentrations of COS, DMS, and CS₂ were 1.8/1.7-, 3.1/4.7-, and 3.7/1.6-fold higher in summer than spring due to the high Chl a concentrations in summer. The mean sea-to-air fluxes of COS, DMS, and CS₂ were 1.3-, 2.1-, and 3.0-fold higher in summer than spring. The sea-to-air fluxes of VSCs indicated that these marginal seas are major sources of VSCs in the atmosphere. The results provide help with a better understanding of the control of VSCs distributions in marginal seas.