The Bohai Sea, one of the most intensive regions for maritime transportation and offshore oil and gas exploitation in China, exerts significant impacts on the air quality of surrounding coastal cities through anthropogenic emissions. However, substantial uncertainties remain regarding how pollutants emitted from ships and offshore oil and gas platforms influence air quality in the surrounding coastal cities under the modulation of sea-land breeze circulations. In this study, Tianjin, the largest port city in Northern China, was selected as the study area. Based on nearly one year of PM_2.5 observations in Tianjin, the contribution of shipping emissions to urban air quality and its meteorological drivers were quantified using source apportionment and machine-learning approaches. Shipping emissions contributed an average of 3.3 μg m^-3 to urban PM_2.5 concentrations, accounting for approximately 8.4% of the total PM_2.5 concentration. In addition, sea-land breeze circulations substantially enhanced the influence of shipping emission. Under easterly and southeasterly wind conditions, shipping-related PM_2.5 contributions reached 6.4 μg m^-3, nearly twice the annual average level. Wind direction, wind speed, and boundary-layer structure were identified as the key meteorological factors controlling shipping-related pollution contributions. Building upon these findings, this study further plans to employ the WRF-Chem model, driven by an East Asian shipping emission inventory and a satellite-derived emission inventory of offshore oil and gas platforms, to conduct a series of scenario-based simulations. The objective is to quantify the spatiotemporal characteristics of the impacts of marine anthropogenic emissions on PM_2.5 concentrations in coastal cities under different seasons and typical meteorological conditions. By integrating ground-based observations, satellite remote sensing, and numerical modeling, this study aims to investigate the impacts of marine anthropogenic emissions on air quality in coastal cities under sea-land breeze circulation conditions, providing scientific support for air pollution control and sustainable development in coastal regions.
 

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