¹³C‐ and ¹⁴C‐based study of sources and atmospheric processing of water‐soluble organic carbon (WSOC) in South Asian aerosols

Abstract

[1] Water-soluble organic carbon (WSOC) is typically a large component of carbonaceous aerosols with a high propensity for inducing cloud formation. The sources of WSOC, which may be both of primary and secondary origins, are in general poorly constrained. This study assesses the concentrations and dual-carbon isotope ( 14 C and 13 C) signatures of South Asian WSOC during a 15-month continuous campaign in [2008][2009]. Total suspended particulate matter samples were collected at Sinhagad (SINH) India and at the Maldives Climate Observatory at Hanimaadhoo (MCOH). Monsoon-driven meteorology yields significant WSOC concentration differences between the dry winter season (0.94 AE 0.43 mg m À3 MCOH and 3.6 AE 2.3 mg m À3 SINH) and the summer monsoon season (0.10 AE 0.04 mg m À3 MCOH and 0.35 AE 0.21 mg m À3 SINH). Radiocarbon-based source apportionment of WSOC not only shows the dominance of biogenic/biomass combustion sources but also a substantial anthropogenic fossil-fuel contribution (17 AE 4% MCOH and 23 AE 4% SINH). Aerosols reaching MCOH after long-range over-ocean transport were enriched by 3-4% in d 13 C-WSOC relative to SINH. This is consistent with particle-phase aging processes influencing the d 13 C-WSOC signal in the South Asian regional receptor atmosphere.Citation: Kirillova, E. N., A. Andersson, R. J. Sheesley, M. Krusa˚, P. S. Praveen, K. Budhavant, P. D. Safai, P. S. P. Rao, and Ö . Gustafsson (2013), 13 C-and 14 C-based study of sources and atmospheric processing of water-soluble organic carbon

Seasonal variations of stable carbon isotopic composition of bulk aerosol carbon from Gosan site, Jeju Island in the East China Sea

“…1). The higher δ 13 C 224 values in the colder months are linked with the higher concentrations of phthalic acid (Fig. 225 and northeastern China in fall and winter (Fig.…”

“…This study explores the usefulness of stable isotopic composition (δ 13 and scattering solar radiation (direct aerosol effect) (Mccormic and Ludwig, 1967; 55 Ramanathan et al, 2001) and acting as cloud condensation nuclei (CCN) (indirect aerosol 56 effect) (Roberts et al, 2003;Twomey, 1974). They also indirectly affect the radiative balance 57 by changing land and ocean biogeochemical cycles through physical forcing or by adding 58 nutrients (Mahowald, 2011).…”

“…Aliquots of CO 2 gas were then 129 introduced online into an isotope ratio mass spectrometer (ThermoQuest, Delta Plus) through 130 a ConFlo II interface (ThermoQuest) to monitor 13 C/ 12 C ratios. The carbon isotopic 131 composition was calculated using the following standard isotopic conversion equation.…”

“…It is well established that oxalic acid is predominantly generated in the 194 atmosphere due to the oxidation of various organics in the gas and aqueous phase (Warneck,195 suggests an increased contribution of sea spray to carbonaceous aerosols. Marine-derived 215 carbonaceous particles are enriched with 13 C in comparison to particles resulting from 216 vehicular emissions, C 3 plants and secondary sources (Fig. 5a).…”

“…5b,c). Higher δ 13 C TC at Gosan than the 261 source regions may be explained by 13 C enrichment during the long-range transport by 262 physical/chemical evolution of organic aerosols and/or mixture of various air masses from 263…”