The photochemical evolution of dissolved black carbon in snow: a case study from the North Cascades

Black carbon (BC) is partially combusted organic material from natural and anthropogenic sources, and is a highly effective driver of melt in the cryosphere. BC has been found in both populated and remote areas around the globe. This study follows the evolution of UV-exposed dissolved BC (DBC) in the cryosphere using the Benzenepolycarboxylic Acid (BPCA) markers B4CA, B5CA, and B6CA. Samples were collected from Mount Baker, Washington, and from both an in situ field study and a controlled photodegradation study, both using natural and anthropogenic BC standards. Both natural and experimental samples had a dominance of B5CA relative to other BPCAs. Many natural samples did not have identifiable quantities of B4CA. Natural snow samples and control samples show overall low DBC values, within range of other cryospheric studies around the world and in the Pacific Northwest United States. The controlled photodegradation study showed an increase in DBC with UV exposure for all standards compared to controls, however diesel soot samples showed