In-stream sources and links between particulate and dissolved black carbon following a wildfire

Abstract

The occurrence of wildfires is expected to increase with the progression of climate change. These natural burn events can drastically alter the geomorphology and hydrology of affected areas and are one of the primary sources of black carbon (BC) in the environment. BC can be mobilized from soils and charcoal in fire-affected watersheds, potentially impacting downstream water quality. In June of 2012, the High Park Fire burned a large portion of the Cache La Poudre River watershed located in the Colorado Rocky Mountains. Seasonal riverine export of BC in both the dissolved (DBC) and particulate (PBC) phase was compared between burned and unburned sections of the watershed during the year following the High Park Fire. There was little difference in overall DBC concentration between sites, however seasonal changes in DBC quality reflected a shift in hydrology and associated DBC source between peak and base flow conditions. PBC export was substantially larger in fire-affected areas of the watershed during periods of overland flow. Our findings suggest that export processes of BC in the particulate and dissolved phase are decoupled in burned watersheds and that, in addition to DBC, the export of PBC could be a significant contributor to the cycling of charcoal in freshwater ecosystems.