Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter

Abstract

at Barrow, Alaska, to characterize the organic mass (OM) in the Arctic aerosol. Organic functional group concentrations and trace metals were measured with FTIR on submicron particles collected on Teflon filters. The OM varied from 0.07 mg m −3 in summer to 0.43 mg m −3 in winter, and 0.35 mg m − 3 in spring, showing a transition in OM composition between spring and winter. Most of the OM in spring could be attributed to anthropogenic sources, consisting primarily of alkane and carboxylic acid functional groups and correlated to elemental tracers of industrial pollution, biomass burning, and shipping emissions. PMF analysis associated OM with two factors, a Mixed Combustion factor (MCF) and an Ocean-derived factor (ODF). Back trajectory analysis revealed that the highest fractions of the MCF were associated with air masses that had originated from northeastern Asia and the shipping lanes south of the Bering Straits. The ODF consisted of organic hydroxyl groups and correlated with organic and inorganic seawater components. The ODF accounted for more than 55% of OM in winter when the sampled air masses originated along the coastal and lake regions of the Northwest Territories of Canada. Frost flowers with organic-salt coatings that arise by brine rejection during sea ice formation may account for this large source of carbohydrate-like OM during the icecovered winter season. While the anthropogenic sources contributed more than 0.3 mg m −3 of the springtime haze OM, ocean-derived particles provided comparable OM sources in winter. Citation: Shaw, P. M., L. M. Russell, A. Jefferson, and P. K. Quinn (2010), Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter, Geophys.

Sources of carbonaceous aerosols and deposited black carbon in the Arctic in winter-spring: implications for radiative forcing

“…Both at Denali and at Barrow, we find that we can largely explain the wintertime OA on the basis of anthropogenic sources and the springtime OA on the basis of open fires. The source attribution in spring is consistent with the work of P. Shaw et al (2010) and Frossard et al (2011), who identified a dominant combustion source for OA at Barrow on the basis of correlations with combustion tracers. attributed most OA at Barrow in winter to oceanic emissions but we find otherwise.…”

“…We use a mass absorption efficiency of 9.5 m 2 g −1 to convert the absorption coefficients to BC mass concentrations based on ARCTAS data (McNaughton et al, 2011). OA observations at Barrow are from P. Shaw et al (2010), who reported seasonal mean concentrations for Mar 2008-Mar 2009 We find that the BC and OA observations at the surface sites in April 2008 are roughly consistent with the mean nearsurface ARCTAS data (Fig. 7), but are more affected by Russian fires.…”

Seasonality of aerosol optical properties in the Arctic

“…This provides a source for sea salt and other marine aerosol during the summer that is much less likely at other times in the year. The result that the same source region overlaps with open ocean in summer and sea ice in winter, and thus yields different aerosol, is supported by similar findings from Shaw et al (2010). TIK, PAL, and SUM are similar in that most of the air mass residence time is spent above land at all times of the year, but especially so in winter.…”

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles

“…The next clear trend is that (iii) the carboxylic acid group contribution accounts for 10 to 40% of OM in the 17 projects for which it was measured. An unexpected feature is the (iv) small Shaw et al (22). n This work, using alkane products derived from Lim and Ziemann (23,24) and monoterpene products based on Capouet et al (25).…”