Long-term (2001–2012) trends of carbonaceous aerosols from
remote island in the western North Pacific: an outflow region of Asian pollutants and dust
Suresh K. R. Boreddy1, Md. Mozammel Haque1,a, and Kimitaka Kawamura1,a1Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan anow at: Chubu Institute of Advanced Studies, Chubu University, Kasugai 487-8501, Japan
Received: 28 Mar 2017 – Accepted for review: 04 Apr 2017 – Discussion started: 05 Apr 2017
Abstract. The present study reports on long-term trends of carbonaceous aerosols in total suspended particulate (TSP) samples collected at Chichijima Island in the western North Pacific during 2001–2012. Seasonal variations of elemental, organic, and water-soluble organic carbon (EC, OC and WSOC) concentrations showed maxima in winter to spring and minima in summer. These seasonal differences in the concentrations of carbonaceous aerosols are associated with the outflows of polluted air masses from East Asia, which are clearly distinguishable from pristine air masses from the central Pacific. The higher concentrations of carbonaceous aerosols during winter to spring are associated with long-range atmospheric transport of East Asian polluted air masses, whereas lower concentrations may be due to pristine air masses from the central Pacific in summer. The annual trends of OC/EC, WSOC and WSOC/OC showed significant (p<0.05) increases during the period of 2001–2012, suggesting that an enhanced secondary formation of organic aerosols (SOA) via photochemical oxidation of anthropogenic and biogenic volatile organic compounds (VOCs) during long-range atmospheric transport. We found a significant increase in nss-K+/EC ratios, demonstrating that biomass burning-derived organic aerosols are increased, while combustion-derived anthropogenic sources are decreased over the western North Pacific. Further, secondary biogenic emissions are also important over the western North Pacific as inferred from a significant increase in the concentrations of methanesulfonate (MSA−, a tracer for biogenic source). We also found significant increases in OC/TC and WSOC/TC ratio, suggesting that contribution of SOA to total carbon (TC) are significantly increased over the western North Pacific followed by long-range atmospheric transport.
Boreddy, S. K. R., Haque, Md. M., and Kawamura, K.: Long-term (2001–2012) trends of carbonaceous aerosols from
remote island in the western North Pacific: an outflow region of Asian pollutants and dust, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-288, in review, 2017.