HR: 14:55h
AN: B13G-06    [Abstracts]
TI: CDOM Characterization of Surface Waters and Groundwater in Tampa Bay, FL: A Spectroscopic and Radioisotopic Approach
AU: * Conmy, R N
EM: rconmy@marine.usf.edu
AF: University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701, United States
AU: Coble, P G
EM: pcoble@marine.usf.edu
AF: University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701, United States
AU: Pyrtle, A J
EM: apyrtle@marine.usf.edu
AF: University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701, United States
AB: Carbonate platforms surrounding subtropical estuaries allow water and chemical constituents to be easily transferred between subsurface aquifers and overlying surficial waters. During times of low rainfall, a significant portion of the water found in the rivers that supply these estuaries originates from springs within the streams themselves. This fluctuation in headwater source often results in variability in the chemistry of the organic material and therefore CDOM optical properties. In addition to the impact of groundwater on stream chemistry, an estuary can be influenced by waters rising directly from beneath the estuary. In the Tampa Bay region, CDOM concentration and optical properties within groundwater wells suggest unique sources and biogeochemical pathways of organic material. Shallow aquifers resemble surface runoff in concentration of DOC and CDOM, as well as in CDOM spectral properties. In contrast, the deep aquifers show higher fluorescence efficiencies and blueshifting of fluorescence. Overall, the depth dependency indicates that CDOM in shallow groundwater has terrestrial sources whereas deep groundwater (where water is estimated to be >10,000 years old) has properties more similar to marine humics. Discussed here will be the results from a March-April 2006 study coupling spectroscopic and radioisotopic techniques to better characterize sources of CDOM in a subtropical estuary. Naturally occurring isotopes of radium (used as a proxy for groundwater contribution) were measured along with CDOM fluorescence, absorption and DOC. Discerning the contribution of CDOM via groundwater, river water and marine water will prove useful in understanding carbon cycling within the Tampa Bay region.
DE: 1055 Organic and biogenic geochemistry
DE: 1830 Groundwater/surface water interaction
DE: 4235 Estuarine processes (0442)
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting