Graduation Year

2009

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Marine Science

Major Professor

Gabriel A. Vargo, Ph.D.

Co-Major Professor

Paula G. Coble, Ph.D.

Committee Member

Kendall L. Carder, Ph.D.

Committee Member

Gary J. Kirkpatrick, Ph.D.

Committee Member

John J. Walsh, Ph.D.

Keywords

fluorescent whitening agents, CDOM, septic, OSTDS, Florida

Abstract

A dual wavelength method was developed for the field detection of optical brighteners

(OBs), fluorescent laundry additives used as indicators of anthropogenic wastes. The

method was quantitative for OBs under variable levels of fluorescent colored dissolved

organic matter (CDOM). Based on excitation at 300-400 nm and 440 and 550 nm

emission, the method assumed a constant ratio of fluorescence due to CDOM alone, even

if absolute amplitude varied. Concentrations of OBs were computed as the difference

between the observed 440 nm emission and the expected CDOM fluorescence at 440 nm,

as extrapolated from the 550 nm fluorescence and established CDOM fluorescence ratio.

Real-time inner filter corrections were based on absorption modeled from 550 nm

fluorescence and from exponential relationships at alternate wavelengths. The effects of

temperature and dissolved oxygen on CDOM fluorescence and computed OB were

quantified but were minimal because effects were comparable between the two

fluorescence regions. Assumptions on the locally conservative behavior of CDOM were

supported in field surveys of sewered and non-sewered areas. Varying water masses were

detected, but OB quantities were detected that did not co-vary with fluorescence alone.

Eleven geographic regions of peninsular Florida and sources of OBs were sampled to

evaluate the method under a broader range of CDOM and to conduct an extensive

detergent spike analysis. Fluorescence data were collected as EEMs and subjected to

PARAFAC modeling, isolating eight spectral factors that could sufficiently describe all

samples. There were no visible regions of the spectra that were unique to detergents or

OBs, but a previously unreported peak in the UV (<230 / 284 ex / em) was tentatively

identified as a detergent surfactant and should be pursued as a potential complementary

indicator of anthropogenic wastes. Limits on EEM fluorescence measurements were

identified: maximum linear range, maximum turbidity, and sensitivity to assumptions. A

sub-sampling technique of EEM data approximated the filter fluorometer readings, was

used to optimize the dual wavelength method, validated the method with spike

recoveries, and presented alternative approaches.

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