@article {332,
	title = {Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion?},
	journal = {Science},
	volume = {323},
	year = {2009},
	note = {id: 1867; 396JL Times Cited:8 Cited References Count:33Y},
	pages = {495-498},
	abstract = {Carbonaceous aerosols cause strong atmospheric heating and large surface cooling that is as important to South Asian climate forcing as greenhouse gases, yet the aerosol sources are poorly understood. Emission inventory models suggest that biofuel burning accounts for 50 to 90\% of emissions, whereas the elemental composition of ambient aerosols points to fossil fuel combustion. We used radiocarbon measurements of winter monsoon aerosols from western India and the Indian Ocean to determine that biomass combustion produced two- thirds of the bulk carbonaceous aerosols, as well as one- half and two- thirds of two black carbon subfractions, respectively. These constraints show that both biomass combustion ( such as residential cooking and agricultural burning) and fossil fuel combustion should be targeted to mitigate climate effects and improve air quality.},
	issn = {0036-8075},
	doi = {10.1126/science.1164857},
	author = {Gustafsson, O. and Krusa, M. and Zencak, Z. and Sheesley, R. J. and Granat, L. and Engstrom, E. and Praveen, P. S. and Rao, P. S. P. and Leck, C. and Rodhe, H.}
}
@article {403,
	title = {Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis},
	journal = {Analytical Chemistry},
	volume = {79},
	year = {2007},
	note = {id: 615; 140ID Times Cited:11 Cited References Count:32},
	pages = {2042-2049},
	abstract = {The relevance of both modern and fossil carbon contamination as well as isotope fractionation during preparative gas chromatography for compound-specific radiocarbon analysis (CSRA) was evaluated. Two independent laboratories investigated the influence of modern carbon contamination in the sample cleanup procedure and preparative capillary gas chromatography (pcGC) of a radiocarbon-dead 3,3{\textquoteright},4,4{\textquoteright},5,5{\textquoteright}-hexachlorobiphenyl (PCB 169) reference. The isolated samples were analyzed for their C-14/C-12 ratio by accelerator mass spectrometry. Sample Delta C-14 values of -996 +/- 20 and -985 +/- 20\% agreed with a Delta C-14 of -995 +/- 20\% for the unprocessed PCB 169, suggesting that no significant contamination by nonfossil carbon was introduced during the sample preparation process at either laboratory. A reference compound containing a modern C-14/C-12 ratio (vanillin) was employed to evaluate process contamination from fossil C. No negative bias due to fossil C was observed (sample Delta C-14 value of 165 +/- 20\% agreed with Delta C-14 of 155 +/- 12\% for the unprocessed vanillin). The extent of isotopic fractionation that can be induced during pcGC was evaluated by partially collecting the vanillin model compound of modern C-14/C-12 abundance. A significant change in the delta C-13 and delta C-14 values was observed when only parts of the eluting peak were collected (delta C-13 values ranged from -15.75 to -49.91\% and delta C-14 values from -82.4 to +4.71\%). Delta C-14 values, which are normalized to a delta C-13 of -25\%, did not deviate significantly (-58.9 to -5.8\%, considering the uncertainty of similar to +/- 20\%). This means that normalization of radiocarbon results to a delta C-13 of -25\%, normally performed to remove effects of environmental isotope fractionation on C-14-based age determinations, also cor-rects sufficiently for putative isotopic fractionation that may occur during pcGC isolation of individual compounds for CSRA.},
	issn = {0003-2700},
	doi = {10.1021/Ac061821a},
	author = {Zencak, Z. and Reddy, C. M. and Teuten, E. L. and Xu, L. and McNichol, A. P. and Gustafsson, O.}
}
@article {515,
	title = {Quantification and radiocarbon source apportionment of black carbon in atmospheric aerosols using the CTO-375 method},
	journal = {Atmospheric Environment},
	volume = {41},
	year = {2007},
	note = {id: 818; 243XB Times Cited:8 Cited References Count:58Y},
	pages = {7895-7906},
	abstract = {To make progress towards linking the atmosphere and biogeosphere parts of the black carbon (BC) cycle, a chemothermal oxidation method (CTO-375), commonly applied for isolating BC from complex geomatrices such as soils, sediments and aquatic particles, was applied to investigate the BC also in atmospheric particles. Concentrations and C-14-based source apportionment of CTO-375 based BC was established for a reference aerosol (NIST RM-8785) and for wintertime aerosols collected in Stockholm and in a Swedish background area. The results were compared with thermal-optical (OC/EC) measurements. For NIST RM-8785, a good agreement was found between the BCCTO-375 concentration and the reported elemental carbon (EC) concentration measured by the "Speciation Trends Network - National Institute of Occupational Safety and Health" method (ECNIOSH) with BCCTO-375 of 0.054+/-0.002gg(-1) and ECNIOSH of 0.067+/-0.008gg(-1). In contrast, there was an average factor of ca. 20 difference between BC(CTO-37)5 and ECNIOSH for the ambient Scandinavian wintertime aerosols, presumably reflecting a combination of BCCTO-375 isolating only the recalcitrant soot-BC portion of the BC continuum and the ECNIOSH metric inadvertently including some intrinsically non-pyrogenic organic matter. Isolation of BCCTO-375 with subsequent off-line radiocarbon analysis yielded fraction modern values (fM) for total organic carbon (TOC) of 0.93 (aerosols from a Swedish background area), and 0.58 (aerosols collected in Stockholm); whereas the fM for BCCTO-375 isolates were 1.08 (aerosols from a Swedish background area), and 0.87 (aerosols collected in Stockholm). This radiocarbon-based source apportionment suggests that contribution from biomass combustion to cold-season atmospheric BCCTO-375 in Stockholm was 70\% and in the background area 88\%. (C) 2007 Elsevier Ltd. All rights reserved.},
	issn = {1352-2310},
	doi = {10.1016/j.atmosenv.2007.06.006},
	author = {Zencak, Z. and Elmquist, M. and Gustafsson, O.}
}
