HR: 1340h
AN: H53G-1510    [Abstracts]
TI: Fingerprinting Dissolved Organic Carbon (DOC) Sources with Specific UV Absorbance (SUVA) and Fluorescence
AU: * van Verseveld, W J
EM: willem.vanverseveld@oregonstate.edu
AF: Oregon State University, 241 Peavy Hall, Department of Forest Engineering, Corvallis, OR 97331, United States
AU: Lajtha, K
EM: lajthak@science.oregonstate.edu
AF: Oregon State University, 2082 Cordley Hall, Department of Botany and Plant Pathology, Corvallis, OR 97331, United States
AU: McDonnell, J J
EM: Jeffrey.McDonnell@oregonstate.edu
AF: Oregon State University, 241 Peavy Hall, Department of Forest Engineering, Corvallis, OR 97331, United States
AB: DOC is an important water quality constituent because it is an important food source for stream biota, it plays a significant role in metal toxicity and transport, and protects aquatic organisms by absorbing visible and UV light. However, sources of stream DOC and changes in DOC quality at storm and seasonal scales remain poorly understood. We characterized DOC concentrations and SUVA (as an indicator of aromaticity) at the plot, hillslope and catchment scale during and between five storm events over the period Fall 2004 until Spring 2005, in WS10, H.J. Andrews, Oregon, USA. This study site has hillslopes that issue directly into the stream. This enabled us to compare a trenched hillslope response to the stream response without the influence of a riparian zone. The main result of this study was that SUVA in addition to DOC was needed to fingerprint sources of DOC. Stream water and lateral subsurface flow showed a clockwise DOC and SUVA hysteresis pattern. Both organic horizon water and transient groundwater were characterized by high DOC concentrations and SUVA values, while DOC concentrations and SUVA values in soil water decreased with depth in the soil profile. This indicates transient groundwater was an important contributor to high DOC concentrations and SUVA values during storm events. During the falling limb of the hydrograph deep soil water and seepage groundwater based on SUVA values contributed significantly to lateral subsurface flow and stream water. Preliminary results showed that fluorescence of stream water and lateral subsurface flow continuously measured with a fluorometer was significantly related to UV-absorbance during a December storm event. Finally, SUVA of lateral subsurface flow was lower than SUVA of stream water at the seasonal scale, indicating a difference in mixing of water sources at the hillslope and catchment scale. Overall, our results show that SUVA and fluorescence are useful tracers for fingerprinting DOC sources.
DE: 1804 Catchment
DE: 1860 Streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting