To investigate the characteristics of atmospheric environment and possible cross-boundary transports in the north of South China Sea, field experiments were carried out on Weizhou Island from March to April, 2015. The concentration and particle size distributions of atmospheric particulate matters were measured, and the concentration characteristics and the source of particulate matters were analyzed in combination with meteorological factors and back trajectory analysis. The results showed that:the PM1, PM2.5 and PM10concentrations were (21±12) μg·m-3, (35±19) μg·m-3, (43±20) μg·m-3, respectively. The mass concentrations of PM1, PM1-2.5 and PM2.5-10 accounted for 50%, 32%,18% of PM10 mass concentrations, respectively. Besides, the number concentrations of particulate matters with particle sizes of 0.5-1 μm, 1-2.5 μm and 2.5-20 μm accounted for 93.5%, 6.1% and 0.4% of the total number concentration, respectively. The particle number concentration was negatively correlated with visibility and air pressure. Backward trajectory analysis showed that air masses from southwest direction accounted for the highest frequency effect (45.9%), in this case, particulate matters with particle sizes of 0.5-1 μm, 1-2.5 μm and 2.5 μm had the minimum number concentration and NO had the highest concentration. Air masses from the east direction accounted for 34.1% of the frequency effect with the minimum SO2concentration and the highest O3 concentration. The concentrations of NO2, NOx, O3 and CO were the minimum when air masses came from the south direction which accounted for 12.5% of the frequency effect. Air masses from the northeast had the lowest frequency effect (7.4%), but had the maximum particle number concentration, mass concentration and the concentration of gaseous pollutants except O3 and NO. Atmospheric fine particles and gaseous pollutants on Weizhou island were affected by transport from Chinese mainland and Southeast Asia. Pollutants from Chinese mainland were mainly from industrial sources, while pollutants from Southeast Asia were mainly from the shipping business inside and outside ports.
Keywords: Weizhou Island; backward trajectory; cluster analysis; number concentration; size distribution.