||In recent years, due to rapid economic and industrial development of mainland China, significant increases of fossil fuel consumption and anthropogenic emissions of air pollutants cause increasing environmental pollution problems. The Matsu Islands is located at the Minjiang Estuary, facing Fuzhou City in the Southeast China. The Matsu Islands have no large-scale industries and pollution sources, which conserved the Islands as an ecological environment. However, the ambient air quality is generally worse than the rural areas of Taiwan, even more serious than urban air quality.|
This study characterized the chemical composition of atmospheric fine particles (PM2.5) at the Matsu Islands. Four sites located at four offshore Islands (Nankan, Beigan, Donyin, and Chukuang) of the Matsu Islands were selected to simultaneously collect fine particles (PM2.5). Three chemical components (i.e. ionic species, metallic elements, carbon content) were analyzed to understand the seasonal variation of PM2.5’s chemical characteristics during the summer of 2013 to the spring of 2014. In order to clarify the region's pollution sources and their contributions, this study applied principal component analysis (PCA), chemical mass balance (CMB) receptor model, and backward trajectory simulation to understand the source apportionment of fine particles, and to explore their temporal variation of sources in different seasons.
The results indicated that the lowest average concentration of fine particles (PM2.5) were observed in the summer. The PM2.5 concentration significantly increased during the northeastern monsoon periods. From the perspective of spatial distribution, it showed that PM2.5 concentration decreased from west to east, and NK site were generally higher than other sites in all seasons. Field measurement results showed that PM2.5 concentrations at the Donyin Islands (DY) in different seasons were always lower than other sampling sites. The results indicated that the PM2.5 concentration highly correlated to long-range transportation, local sources, and atmospheric dispersion condition.
Chemical composition analysis showed that the most abundant water-soluble ionic species of fine particles (PM2.5) were secondary inorganic aerosols (SO42-, NO3-, and NH4+) which accounted for 70% of total ions and mainly SO42-and NO3-, resulting in suspended particulate matter NR were less than unity in the Matsu Islands. The NR ratio of fine particles (PM2.5) were smaller than unity, indicating that atmospheric fine particles were mostly acidic. The metallic elements Al, Ca, Fe, K, Mg, dominated the chemical species of particles, other trace metals (eg, Cd, As, Ni, and Cr) concentration increased during the northeastern monsoon periods. Organic carbons (OC) were the main species in all seasons, and OC/EC value was generally higher than 2.2.
Results obtained from PCA and CMB receptor modeling showed that major sources of fine particles (PM2.5) in the Matsu Islands were soil dusts, secondary inorganic aerosols, industrial pollution, and agricultural burning. During the northeastern monsoon and poor air quality periods, the major transportation route was northern transportation (N-type) and anticyclonic outflow (AO-type), in which pollution sources and their contribution were higher during these period. The results of CMB receptor model during the intensive sampling periods were consistent very well with the soil dusts and secondary inorganic aerosols in the Matsu Islands. Agricultural burning in winter was generally higher than other sources, which contributed from 7.42% to 15.17% of fine particles (PM2.5) Overall speaking, cross-boundary transport accounted for 66~84%, showing that the Matsu Islands was significantly influenced by the cross-boundary transport.