Field measurements of aerosols were conducted on Xiaoyangshan Island in the East China Sea in May 2006 to investigate the impact of anthropogenic air pollutants to the coastal environment. MM5/CMAQ was used to model the development of the episode and identify the sources of major ionic species during the episode. The results showed that the major ionic species in TSP were SO₄^2-, NO₃^- and NH₄⁺, which accounted for about 76% of the total water soluble ions (TWSI). The mean concentrations of SO₄^2-, NO₃^- and NH₄⁺ were 20.9, 10.4 and 5.1 µg m^-3, respectively, and the peak values on a foggy day were 69.87, 38.48 and 22.75 µg m^-3, respectively. The most abundant ionic species was SO₄^2-. The increase of SO₄^2- concentration was found to be significantly correlated with the decrease of the atmospheric visibility (correlation coefficient = 0.82). Process analysis implied that advection, diffusion and cloud chemical processes contributed to this pollution episode. Backward trajectory analysis revealed that the airflow on the foggy and most polluted day during the sampling campaign was westerly, i.e., from the continent. Both the measured data and modeling results showed that the coastal atmosphere was seriously affected by terrestrial pollutants in the continental outflow.