Rocky Mountain Section - 64th Annual Meeting (9–11 May 2012)

Paper No. 2
Presentation Time: 8:45 AM


PERDRIAL, Julia N.1, VAZQUEZ-ORTEGA, Angelica2, MCINTOSH, Jennifer3, HARPOLD, Adrian4, PORTER, Courtney5, ZAPATA-RIOS, Xavier5, GUTHRIDGE, Lauren2, BROOKS, Paul D.6 and CHOROVER, Jon7, (1)Soil, Water and Environmental Sciences, University of Arizona, 1177 E. 4th Street, Tucson, AZ 85721, (2)Soil, Water and Environmental Sciences, University of Arizona, 1177 E. 4th street, Tucson, AZ 85721, (3)Hydrology & Water Resources, University of Arizona, Tucson, AZ 85721, (4)Instaar, University of Colorado, 1560 39th st, Boulder, CO 80303, (5)Hydrology & Water Resources, University of Arizona, 1133 E. North Campus Dr, Tucson, AZ 85721, (6)Department of Hydrology and Water Resources, Univ of Arizona, Tucson, AZ 85721, (7)Department of Soil, Water and Environmental Science, University of Arizona, 525 Shantz Bldg, Tucson, AZ 85721-0038,

Wild fires present an important disturbance to critical zone (CZ) structure and function by significantly impacting CZ carbon and water balance. During wildfires, a considerable portion of the CZ carbon pool is oxidized and directly returned to the atmosphere. Streams present another important pathway for carbon to leave the CZ, and long term post-burn effects on CZ carbon export can be monitored.

To quantify fire impacts on stream water carbon, stream water samples from the Jemez river that drains severely burned areas, were analyzed for dissolved organic and inorganic carbon (DOC and DIC) and fluorescence spectroscopic properties (including PARAFAC analysis). Additionally, to quantify impacts from ash and burned soil on stream water, water extractable soil organic matter (WEOM) was analyzed. Compared to underlying less burned organic and mineral soil, ash samples showed typically higher DIC concentrations and a decrease of reduced hydroquinone –like fluorescence. This signature is also visible in stream waters with significantly higher post-burn DIC concentrations (average of 11.5 mg/L between August and December 2011 vs. 6.9mg/L for pre-burn samples between March and June 2011). OM analyses of stream water additionally shows significantly higher abundances of oxidized quinone (PARAFAC component C-2, (Cory and McKnight, 2005)) and decreased abundances of protein fluorescence in post-burn samples. These results are in agreement of the oxidation OM during high intensity fires and the decrease of typical microbial signatures in OM (especially protein). Stream water quality reflected effects of the Las Conchas wildfire through the year 2011.

Cory, R. M. and McKnight, D. M. 2005. Fluorescence Spectroscopy Reveals Ubiquitous Presence of Oxidized and Reduced Quinones in Dissolved Organic Matter. Environ. Sci. Technol. 39. 8142-8149.10.1021/es0506962.