HR: 1400h
AN: H33B-05    [Abstracts]
TI: Storm to Seasonal Nitrate Flushing and Relationship to Hydroclimatic Conditions
AU: * Barco, J
EM: ojbarco@ucla.edu
AF: Janet Barco, 3734 Clarington Ave. Apt. 11, Los Angeles, CA 90034, United States
AU: Wessel, C
EM: cjwessel@ucla.edu
AU: Gunawan, S
EM: stephaniecg@ucla.edu
AU: Hogue, T S
EM: thogue@seas.ucla.edu
AF: Janet Barco, 3734 Clarington Ave. Apt. 11, Los Angeles, CA 90034, United States
AB: Coupled hydrological and geochemical cycles have historically been used to understand the mechanisms controlling chemical export at the watershed scale. Numerous studies have focused on stream geochemistry dynamics and particularly on the effects of nitrogen deposition on catchments and ecosystems. However, few studies have evaluated the variability in nitrate behavior in watersheds with different climate and hydrologic characteristics. Furthermore, storm nitrate dynamics (flushing) and corresponding relationship to discharge patterns, precipitation intensity, atmospheric deposition, and watershed properties is an area with few published studies. In the current study, we utilize hydrologic, geochemical and atmospheric data to better understand the primary processes controlling nitrate dynamics at monthly and seasonal time scales in ten watersheds located in the U.S. Stream data (discharge and nitrate concentrations) was obtained from the United States Geological Survey (USGS). Atmospheric deposition data was gathered from regional National Atmospheric Deposition Program (NADP) sites. Collected data were assessed to evaluate nitrate dynamics for the period 2000-2006. Intra-storm nitrate variability was also evaluated in a watershed in Southern California (Arroyo Seco) where estimates of dry deposition are considered some of the highest in North America. Results from our analyses show that nitrate concentration appears to respond differently in the studied watersheds, exhibiting dilution effects in some watersheds and concentration effects in others. Discharge and nitrate concentrations during the 2009 winter reveal that the Arroyo Seco watershed is characterized by distinctive flushing of nitrates within storms. The role of specific hydrological events (size, intensity and duration) on the nitrate mobilization proved to be important as well as the accumulated nitrate pool available for mobilization. In general, results show a strong linkage between hydrological and biogeochemical controls of nitrate exports. Results from this study support previous studies regarding nitrate flushing during wet seasons and also add new insight on enhanced export in areas with increased deposition rates of nitrates.
DE: 0496 Water quality
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1860 Streamflow
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2009 Joint Assembly