03366nas a2200205 4500008004100000245009200041210006900133260001200202300001400214490000700228520274200235100001902977700001802996700001903014700001503033700001903048700002303067700002403090856004603114 2017 eng d00aDissolved black carbon in the global cryosphere: Concentrations and chemical signatures0 aDissolved black carbon in the global cryosphere Concentrations a c06/2017 a6226-62340 v443 a

Black carbon (BC) is derived from the incomplete combustion of biomass and fossil fuels and can enhance glacial recession when deposited on snow and ice surfaces. Here we explore the influence of environmental conditions and the proximity to anthropogenic sources on the concentration and composition of dissolved black carbon (DBC), as measured by benzenepolycaroxylic acid (BPCA) markers, across snow, lakes, and streams from the global cryosphere. Data are presented from Antarctica, the Arctic, and high alpine regions of the Himalayas, Rockies, Andes, and Alps. DBC concentrations spanned from 0.62 μg/L to 170 μg/L. The median and (2.5, 97.5) quantiles in the pristine samples were 1.8 μg/L (0.62, 12), and nonpristine samples were 21 μg/L (1.6, 170). DBC is susceptible to photodegradation when exposed to solar radiation. This process leads to a less condensed BPCA signature. In general, DBC across the data set was composed of less polycondensed DBC. However, DBC from the Greenland Ice Sheet (GRIS) had a highly condensed BPCA molecular signature. This could be due to recent deposition of BC from Canadian wildfires. Variation in DBC appears to be driven by a combination of photochemical processing and the source combustion conditions under which the DBC was formed. Overall, DBC was found to persist across the global cryosphere in both pristine and nonpristine snow and surface waters. The high concentration of DBC measured in supraglacial melt on the GRIS suggests that DBC can be mobilized across ice surfaces. This is significant because these processes may jointly exacerbate surface albedo reduction in the cryosphere. 

1 aKhan, Alia, L.1 aWagner, Sasha1 aJaffé, Rudolf1 aXian, Peng1 aWilliams, Mark1 aArmstrong, Richard1 aMcKnight, Diane, M. uhttp://doi.wiley.com/10.1002/2017GL07348501706nas a2200145 4500008004100000245009500041210006900136260001200205520122100217100001901438700001901457700001401476700002401490856004601514 2016 eng d00aDissolved black carbon in Antarctic lakes: chemical signatures of past and present sources0 aDissolved black carbon in Antarctic lakes chemical signatures of c06/20163 a

The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as sentinels for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the chemical signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody chemical signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in contemporary black carbon from fossil fuel combustion. Comparison of samples collected 25 years apart from the same lake suggests that the enrichment in anthropogenic black carbon is recent. Differences in the chemical composition of dissolved black carbon among the lakes are likely due to biogeochemical processing such as photochemical degradation and sorption on metal oxides.

1 aKhan, Alia, L.1 aJaffé, Rudolf1 aDing, Yan1 aMcKnight, Diane, M. uhttp://doi.wiley.com/10.1002/2016GL068609