Articles | Volume 17, issue 4
https://doi.org/10.5194/acp-17-3199-2017
https://doi.org/10.5194/acp-17-3199-2017
Research article
 | 
02 Mar 2017
Research article |  | 02 Mar 2017

Atmospheric aerosol compositions over the South China Sea: temporal variability and source apportionment

Hong-Wei Xiao, Hua-Yun Xiao, Li Luo, Chun-Yan Shen, Ai-Min Long, Lin Chen, Zhen-Hua Long, and Da-Ning Li

Abstract. In order to evaluate impacts of different source emission on marine atmospheric particles over the South China Sea (SCS), major inorganic ionic concentrations (Na+, Cl, SO42−, Ca2+, Mg2+, K+, NH4+ and NO3) were determined in total suspended particulates (TSPs) at Yongxing Island, from March 2014 to February 2015. The annual average concentration of TSPs was 89.6 ± 68.0 µg m−3, with 114.7 ± 82.1, 60.4 ± 27.0 and 59.5 ± 25.6 µg m−3 in cool, warm and transition seasons, respectively. Cl had the highest concentration, with an annual average of 7.73 ± 5.99 µg m−3, followed by SO42− (5.54 ± 3.65 µg m−3), Na+ (4.00 ± 1.88 µg m−3), Ca2+ (2.15 ± 1.54 µg m−3), NO3 (1.95 ± 1.34 µg m−3), Mg2+ (0.44 ± 0.33 µg m−3), K+ (0.33 ± 0.22 µg m−3) and NH4+ (0.07 ± 0.07 µg m−3). Concentrations of TSPs and the major ions showed seasonal variations, which were higher in the cool season and lower in the warm and transition seasons. Factors of influence were wind speed, temperature, relatively humidity, rain and air mass source region. Back trajectories, concentration-weighted trajectories (CWTs), and positive matrix factorization (PMF) of chemical compositions were analyzed for source apportionment, source contribution and spatiotemporal variation of major ions. Back trajectories and CWTs showed that air masses at Yongxing Island were mainly from the northeast, southwest and southeast in the cool, warm and transition seasons, respectively. The PMF results showed that 77.4 % of Na+ and 99.3 % of Cl were from sea salt; 60.5 % of NH4+ was from oceanic emission. Anthropogenic sources were very important for atmospheric aerosols over the island. Secondary inorganic aerosol of SO2 and NOx from fossil fuel combustion (especially coal in Chinese coastal regions) was the dominant source of NO3 (69.5 %) and SO42− (57.5 %).

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Short summary
We collected 1 year of aerosol samples at Yongxing Island in the South China Sea. The concentrations of TSP and all major inorganic ions showed seasonal variations, with higher concentrations in the cool season and lower in the warm season; 60.5 % of NH4+ was from oceanic emission. Secondary inorganic aerosol of SO2 and NOx from fossil fuel combustion (especially coal in Chinese coastal regions) was the dominant source of NO3 (69.5 %) and SO42− (57.5 %).
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