Enhanced Marine VOC Emissions Driven by Terrestrial Nutrient Inputs and Their Impact on Urban Air Quality in Coastal Regions

Global ocean significantly contributes to atmospheric volatile organic compounds (VOCs), yet the characteristics, drivers, and impacts of marine VOC emissions on coastal air quality remain poorly understood due to limited marine-terrestrial data integration. Therefore, we conducted a study in the East China Sea─a region with high VOC emission potential─and a nearby coastal city in the Yangtze River Delta─a background receptor site. Seawater VOC emissions showed marked spatial variability, with alkenes forming an important component. Terrestrial inorganic nutrient inputs boosted marine primary productivity, elevating VOC concentrations and emissions. Interestingly, in the coastal city, severe photochemical pollution occurred when air masses originated predominantly from the sea. Although maritime air masses contained fewer VOCs, emissions from high-productivity seawater and shipping increased reactive alkene levels. Additionally, higher temperatures, stronger solar radiation, and reduced NO titration effects over the sea facilitated ozone formation. By integrating marine-terrestrial observations, this study underscores the impact of pollutant emissions from high-productivity seas on coastal air quality, particularly through secondary formation during long-range transport. The link between coastal seawater eutrophication and air photochemical pollution emphasizes the need for coordinated air and water pollution control in coastal cities. These findings may apply to other similar coastal environments worldwide.