The ocean is an important source of atmospheric gases and particles that alter atmospheric chemistry, coastal air quality, and climate. As terrestrial emissions decline and climate change continues, quantifying marine emissions and their effects on key atmospheric constituents is increasingly important for air-quality management and regional climate assessment.
To investigate marine volatile organic compounds (VOCs) and their influence on coastal air quality, we conducted coordinated observations over the East China Sea (ECS) and at a coastal site in Haiyan, Zhejiang. The ECS was generally a net VOC source, particularly for alkenes such as ethylene. Concentrations and fluxes varied strongly in space, with hotspots in nearshore waters. Their low salinity, high nutrient levels, and shipboard incubation results suggest that land-derived nutrients enhanced primary productivity and VOC production. At Haiyan, ocean-dominated air masses were frequently associated with severe photochemical pollution. Although total VOC mixing ratios were relatively low, emissions from productive waters and ships increased both the abundance and fraction of reactive alkenes. Higher temperatures, stronger radiation, and weaker NO titration over the ocean further promoted ozone formation and accumulation. These results demonstrate that emissions from productive marine regions can substantially affect coastal air quality, particularly through secondary production during transport, and suggest that seawater eutrophication may aggravate photochemical pollution.
Marine atmospheric particles also strongly affect coastal air quality, public health, and climate, but their sources are difficult to resolve because of interactions between continental outflow and marine emissions. We conducted five shipborne campaigns across coastal and open-ocean regions, complemented by simulation experiments. Rapid changes in air-mass origin and strong spatial heterogeneity in anthropogenic and marine emissions obscured consistent nearshore–offshore gradients. Nevertheless, marine particulate matter remained relatively abundant. Continental air masses passing over productive coastal waters carried stronger anthropogenic and marine signals, increasing particulate mass and organic fractions. Anthropogenic and marine biogenic emissions also enhanced atmospheric oxidation and acidity, promoting organic functionalization and fragmentation and producing molecules with greater compositional diversity, lower molecular mass, and higher oxidation state and aromaticity. CHO compounds dominated all regions. Anthropogenic emissions increased all molecular classes, whereas CHOS compounds responded particularly strongly to marine biogenic inputs, consistent with enhanced release of dimethyl sulfide during phytoplankton blooms. These findings provide molecular-level evidence that marine biological activity regulates the abundance, composition, and evolution of atmospheric particles in marine environments.

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