Diane M. McKnight

Dissolved black carbon in the global cryosphere: Concentrations and chemical signatures

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 0.62u2009µg/L to 170u2009µg/L. The median and (2.5, 97.5) quantiles in the pristine samples were 1.8u2009µg/L (0.62, 12), and non-pristine samples were 21u2009µg/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 dataset was comprised 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 non-pristine snow and surface waters. The high concentration of DBC measured in supra-glacial melt on the GRIS suggests DBC can be mobilized across ice surfaces. This is significant because these processes may jointly exacerbate surface albedo reduction in the cryosphere.