Inter-comparison of Chemical Composition and Originality of Atmospheric PM10 at Coastal Regions and Offshore Islands in the Subtropical East Asia

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Inter-comparison on the chemical characteristics, spatiotemporal variation, and source originality of atmosphere PM10 at the coastal regions and offshore islands of subtropical region in East Asia was investigated. A total of six sampling sites including three coastal and three island sites over the Minjiang estuary were selected for simultaneously manually sampling PM10 to investigate the differences of coastal and island PM10 concentration, chemical properties, and emission sources. After sampling, an ion chromatographer (IC) was used to analyze the concentration of major anions (F−, Cl−, SO42−, and NO3−) and cations (NH4+, K+, Na+, Ca2+and Mg2+). The metallic elements (Na, Ca, Al, Fe, Mg, K, Zn, Cr, Ti, Mn, Ni, Pb, and Cd) of PM10 were measured with an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The carbonaceous contents, including elemental, organic, and total carbons (OC, EC, and TC), of PM10 were analyzed with an elemental analyzer (EA). The source apportionment of PM10 was further resolved by a receptor model based on chemical mass balance (CMB). Field measurement results showed that high concentrations of PM10 (102 ± 25 μg/m3) were commonly observed from late fall to early winter. The PM10 concentration showed a consistently descending trend from the west coastline to the far east islands, with the highest PM10 concentration at the coastal site (Site HQ) and the lowest at the far east island site (Site DY) in all seasons. Secondary inorganic aerosols (SIAs) and crustal materials were two most abundant compounds in PM10. Increasing anthropogenic trace elements was commonly observed in spring and winter, while northern monsoons were blown. High OC/EC ratios showed that secondary organic aerosols (SOAs) could be formed in the atmosphere of Minjiang estuary. Results from CMB receptor modeling indicated that the major sources of atmospheric PM10 at the coastal and offshore island regions of the Minjiang estuary were soil dusts (13–33%), secondary aerosols (15–30%), transport emissions (11–17%), sea salts (8–27%), and agricultural debris burning (2–8%). Particularly, during the poor air quality periods, a rising contribution of industrial emissions (1–16%) was resolved, suggesting that atmospheric PM10 over the Minjiang estuary was mainly attributed to cross-boundary transport rather than local emissions.