Non-methane hydrocarbons in the continental seas of China: Spatiotemporal variability, controlling factors, and...

Coastal regions, as hotspots for non-methane hydrocarbons (NMHCs) emissions, warrant more consideration for their vital impacts on marine climate regulation. This study examined the spatiotemporal distributions, emissions, and environmental effects of NMHCs in the Bohai Sea (BS) and Yellow Sea (YS) during summer and winter. The NMHC concentrations show clear spatial and seasonal variability, with higher levels observed in summer. The horizontal distributions of isoprene closely mirrored chlorophyll-a (Chl-a), suggesting a strong linkage to phytoplankton activities, while other NMHCs appeared to be associated with photochemical processes. Atmospheric alkane concentrations declined from inshore regions to offshore regions indicating the significant input of terrestrial sources, whereas alkenes were predominantly emitted from the ocean. The NMHC sea-to-air fluxes ranged from 11.8 to 306 nmol m^-2 d^-1, underscoring the importance of coastal regions as major sources of atmospheric NMHCs. These emissions significantly promote the formation of secondary organic aerosol (SOA) and ozone (O₃), thereby exerting a vital impact on the marine environment.