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- Title
One-year observations of carbonaceous and nitrogenous components and major ions in the aerosols from subtropical Okinawa Island, an outflow region of Asian dusts.
- Authors
B. Kunwar; K. Kawamura
- Abstract
Ambient aerosol samples (TSP, n = 50), collected at subtropical Okinawa Island, Japan, an outflow region of Asian dusts in the western North Pacific, were studied for organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble total nitrogen (WSTN), water-soluble organic nitrogen (WSON) and major ions to better understand the long-range atmospheric transport and formation and transformation pathways of East Asian aerosols. Concentrations of OC, EC, WSOC, WSTN and WSON ranged from 0.76 to 7.1 µgm-3 (av. 1.74±1.03 µgm-3), 0.07-0.96 µgm-3 (0.28±0.19 µgm-3), 0.27-1.9 µgm-3 (0.73±0.38 µgm-3), 0.77 to 3.03 µgm-3 (0.58±0.46 µgm-3) and 0 to 2.2 µgm-3 (0.12±0.23 µgm-3), respectively. The average concentration of OC is higher in growing seasons; spring (2.36 µgm-3) and summer (1.79 µgm-3). Similarly, the highest concentrations of EC and WSOC were found in spring (av. 0.41 µgm-3 and 0.95 µgm-3, respectively) followed by winter (0.37 and 0.90 µgm-3) whereas the lowest concentrations were found in summer (0.19 and 0.52 µgm-3, respectively). In contrast, higher concentrations of WSTN were observed in winter (0.86 µgm-3) and lower concentrations were observed in summer (0.37 µgm-3) and autumn (0.34 µgm-3). Similarly, higher concentrations of WSON were observed in early summer (av. 0.26 µgm-3) due to the emission from marine biota. The high OC/EC (av. 7.6) and WSOC/OC (44 %) ratios suggest the secondary formation of organic aerosols. The OC/EC ratios, correlation analyses between OC and EC (r = 0.81), and OC and MSA- (0.81) in spring suggest that springtime aerosols are influenced by additional marine and terrestrial biogenic sources. The correlation analyses of Ca2+ and TSP in spring suggests a significant influence from dust whereas the higher concentrations of NO3- and nss-SO42- in winter suggest the influence from anthropogenic sources including biomass burning, vehicular emission and coal combustion. NH4-N/WSTN ratios peaked in winter (0.56), indicating an important contribution of biomass burning to WSTN in cold season. In contrast, higher NO3-N/WSTN ratio in spring than winter suggests that vehicular emissions are significant in spring. Correlation analyses of major ions suggest that NH4+ and Ca2+ play major role in the neutralization of aerosols forming NH4HSO4, (NH4)2SO4 and CaSO4.
- Subjects
OKINAWA Island (Japan); JAPAN; CARBONACEOUS chondrites (Meteorites); ATMOSPHERIC aerosols; DUST; ATMOSPHERIC transport; CALCIUM ions; BIOMASS burning; COAL combustion
- Publication
Atmospheric Chemistry & Physics Discussions, 2013, Vol 13, Issue 8, p22059
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acpd-13-22059-2013