HR: 11:35h
AN: H42C-06    [Abstracts]
TI: Tracer studies of transport processes in the tidal Hudson River: A comparison of SF$_{6}$ and a fluorescent dye
AU: * Ho, D T
EM: david@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: * Ho, D T
EM: david@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027 United States
AU: Schlosser, P
EM: schlosser@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Schlosser, P
EM: schlosser@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027 United States
AU: Schlosser, P
EM: schlosser@ldeo.columbia.edu
AF: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027 United States
AU: Houghton, R
EM: houghton@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Caplow, T
EM: tc144@columbia.edu
AF: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027 United States
AB: Fluorescent dyes have frequently been used to study transport processes such as net advection and longitudinal dispersion in rivers. Recently, it has been shown that sulfur hexafluoride (SF$_{6}$) is a viable alternative to dyes, while offering many advantages. For example, SF$_{6}$ is less expensive than dye, and has a greater dynamic range. As a result, experiments can be conducted on longer timescales and greater spatial scales. Also, because SF$_{6}$ is a gas, its loss across the air-water interface can be used to quantify the gas transfer velocity, which affects the fate of volatile and semi-volatile compounds. Here, we present results from a dual tracer release conducted in the tidal Hudson River using a fluorescent dye (Fluorescein; C$_{20}$H$_{10}$O$_{5}$Na$_{2}$) and SF$_{6}$. Fluorescein was surveyed for 5 days (until it was undetectable) and SF$_{6}$ was surveyed for 11 days. The dye resolves initial vertical mixing on the first day, and then net advection and longitudinal dispersion on subsequent days, while the SF$_{6}$ provides information on net advection and longitudinal mixing on larger spatial and longer time scales. Transport processes (net advection and longitudinal dispersion) calculated from the two methods were consistent for the first four days, and start to deviate on the fifth day when the signal to noise ratio of the dye deteriorated. Initial results indicate that for the first four days, net advection was 3.0 $\pm$ 0.1 km d$^{-1}$, and longitudinal dispersion coefficients were 24.6 $\pm$ 6.6 and 19.6 $\pm$ 2.5 m$^{2}$ s$^{-1}$ for SF$_{6}$ and dye, respectively. The SF$_{6}$ results for the longer timescale and larger special scale will be discussed in the context of similar experiments conducted in other reaches of the tidal Hudson River.
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting