Vegetation and tides regulate the emissions of volatile sulfur compounds from intertidal wetland sediments

Abstract

Volatile sulfur compounds (VSCs)—carbonyl sulfide (COS), dimethyl sulfide (DMS), and carbon disulfide (CS 2 )—play critical roles in atmospheric chemistry. Nevertheless, quantitative understanding of VSC exchange dynamics in coastal wetland ecosystems remains limited. Here, we quantified the sediment‐air fluxes of these VSCs across vegetated ( Spartina alterniflora and Suaeda glauca ) and unvegetated mudflat habitats via year‐round field observations in a temperate intertidal wetland. We found that S. alterniflora sediments exhibited net emissions of COS (4.61 ± 9.19 nmol m −2 s −1 ), DMS (10.25 ± 12.35 nmol m −2 s −1 ), and CS 2 (5.77 ± 7.29 nmol m −2 s −1 ), while S . glauca and mudflats exhibited variable sink–source dynamics. VSC fluxes from S. alterniflora habitats significantly exceeded those from other zones due to high root sulfate and total sulfur contents, as well as microbial organisms and temperature‐dependent microbial activity related to sulfur metabolism. The DMS flux in S. alterniflora zones decreased by 33–224% after ebb tide compared to before flooding, with principal component analysis identifying phase‐specific controls: pre‐flood fluxes were associated with porewater chemistry (pH, redox potential) and atmosphere (water content, pressure) coupling, while post‐ebb fluxes were governed by ionic gradients (conductivity) and residual moisture (water content). Tidal simulation experiments revealed the joint influences of illumination, water content, and anaerobic processes on VSC production, where anaerobic conditions suppressed DMS and CS 2 formation but enhanced COS emission in the dark. These findings establish that coastal VSC fluxes are regulated by the interplay between macrophyte‐mediated sediment biogeochemistry and tidal pumping. This provides mechanistic insights into wetland sulfur cycle modeling.

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