Source Characterization of Dissolved Organic Matter in Southwest Florida Estuaries by 

UV-visible and Fluorescence Analysis

 

^1,2Xiaoqiao Lu, ¹Joseph N. Boyer, and ^1,2Rudolf Jaffe*

 

¹Southeast Environmental Research Center, and ²Department of Chemistry, Florida International University, Miami, FL 33199, USA.  

*Author to whom correspondence should be addressed.

 

Abstract

Measurements of dissolved organic matter (DOM), UV-visible, and fluorescence were performed to monitor and characterize spatial and temporal variability in concentrations, optical properties, and sources of DOM samples collected from surface water in the southwest coast of Florida between March and May 1999. Concentrations of DOM in the surface water ranged from 3.18 to 20.4 ppm and decreased from the upper estuarine to the coastal areas. An attempt to monitor sources and degree of degradation of DOM using an UV-visible index, (a₂₅₄/a₄₃₆), and a fluorescence emission index, (f_450/500), was unsuccessful. This was most likely caused by the spectroscopic response of DOM freshly leached from local plant biomass in the Florida Everglades, suggesting that the application of these spectroscopic parameters has limitation in this system. Synchronous fluorescence spectra provided useful information on DOM components. The peak at about 285 nm could be due to proteins derived from algae or DOM freshly leached from mangrove leaves. The peaks at about 350, 385, and 460 nm are most likely associated with humic like substances. Comparison of the relative peak intensities of the synchronous fluorescence spectra of the DOM samples versus salinity or a₂₅₄ nm may make it possible to monitor source variation and transport process of the DOM in the region.