Current air–sea VOC flux models parameterize the gas-transfer coefficient (K) solely by wind speed, neglecting the near-surface atmosphere and the key biogeochemical interface, the sea surface microlayer (SML), which introduces uncertainty in emission estimates. Temperature, salinity, dissolved organic matter, and surfactants in the SML regulate interfacial resistance and thus VOC emissions, yet incorporating these factors into K parameterization is essential to overcome model limitations and improve flux accuracy. Complex coastal waters, influenced by terrestrial inputs, biological activity, and anthropogenic emissions, provide ideal natural environment for elucidating multi-factor regulatory mechanisms and optimizing the K formula. In this study, we have invented a low-disturbance floating air chamber with solenoid valves and a self-developed rotating-drum microlayer collector (adjustable speed/depth, ~50–200 μm thickness, 3 L volume), which are used to collect near-surface atmosphere and sea surface microlayer, respectively. Single- and multi-factor gradient experiments (temperature, wind speed, salinity, DOM) were conducted to establish a parameterized formula K=f(U,T,S,D), validated against floating-chamber fluxes in the field. Comprehensive sampling was performed in Pearl River Delta coastal zones (mangroves, ports, residential areas, mariculture) for in-situ or PTR-TOF-MS analysis. Preliminary results show that the multi-factor optimized K more accurately characterizes VOC exchange fluxes across functional zones, revealing SML biogeochemical influences on source-sink patterns, and the improved model provides more accurate flux estimates applicable to other coastal regions.

 

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