Atmospheric aerosol compositions over the South China Sea: temporal variability and source apportionment
- 1Laboratory of Atmospheric Environment, Key Laboratory of Nuclear Resources and Environment (Ministry of Education), East China University of Technology, Nanchang 330013, China
- 2School of Water Resources and Environmental Engineering, East China University of Technology, Nanchang 330013, China
- 3College of Fisheries, Guangdong Ocean University, Zhanjiang 524088, China
- 4State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
- 5Xisha Deep Sea Marine Environment Observation and Research Station, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Sansha 573199, China
- 6College of Earth Sciences, University of Chinese Academy of Science, Beijing 100049, China
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 %).