Title

Using spectro-fluorometry and fluorescent dye-tracing to investigate hydrologic processes in organic-rich environments

Date of Award

2005

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor(s)

Donald I. Siegel

Keywords

Spectrofluorometry, Fluorescent, Dye-tracing, Organic-rich, Hydrogeology

Subject Categories

Earth Sciences | Environmental Sciences | Physical Sciences and Mathematics

Abstract

For the past two centuries natural and artificial fluorescence have been used to determine hydrologic flow paths in organic-poor systems such as karstic carbonate formations. However, using fluorescent dye-tracing in organic-rich environments is difficult because of the large, natural and/or anthropogenic fluorescence background intensities.

I focused my study on three different places where organic substances in surface or ground water occur at high concentrations: (1) wetlands in the Croton Watershed, NY that provide New York City with drinking water, (2) a cutting-oil contaminated industrial site in western NY, and (3) meromictic Lake Cadagno, Switzerland, where bacteria thrive in the chemocline. In the case of the Croton Watershed wetlands, I tested the hypothesis that the fluorescence of natural organic substances can be used to distinguish wetland types, the amounts of DOC in the wetland surface waters, and the extent to which septic organic matter has entered rivers and wetlands. In the case of the oil contaminated industrial site, I tested the hypotheses that natural fluorescence of the degrading oil can be used to characterize the position of the plume and that organic fluorescent dyes can be used in this highly contaminated setting to distinguish ground water flow paths. Finally, at Lake Cadagno, I tested whether a dye-tracing test could evaluate the assumption that the biocline behaves as a hydraulic no-flow boundary, completely separating meromictic from surface waters.

The results of the Croton study showed that synchronous spectro-fluorometry can be used to quickly estimate the overall natural and anthropogenic organic load in surface water along streams or ground water flow paths in organic-rich environments. Additionally the background fluorescence is a bulk indicator for DOC and g440 similar to how specific conductance is an indicator for total dissolved inorganic solids. The results of the oil-contaminated aquifer study showed that conventional dye-tracing is possible in a heavily oil-contaminated aquifer despite the common thinking that organic dyes cannot be used in organic-rich environments. The results of the Cadagno study showed that dye-tracing can help trace and understand complex circulation patterns in alpine meromictic lakes and may be used to estimate sub-aquatic spring discharge.

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