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Chromophoric dissolved organic matter in coastal rainwater

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Kelly Jo Gordon (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Robert Kieber

Abstract: Chromophoric dissolved organic matter (DOM) was measured in 37 rain events in Wilmington, NC, between September 15, 2005 to September 6, 2006. Each rain event was analyzed via 3D fluorescence, UV-Vis absorption spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and dissolved organic carbon measurements were acquired. All rain events had measurable CDOM, although there was much variability between events. Chromophoric DOM was found in both the C18 extract (hydrophobic) and the C18 filtrate (hydrophilic) fraction, but surprisingly a large fraction of the chromophoric DOM is relatively hydrophilic (~50%). Using NMR, it was determined that in all rain events the majority of the protons were alkyl. A strong positive correlation was found between the fluorescence and the overall integration of the NMR spectra. A correlation was also found between fluorescence and the various integral regions of the NMR with the greatest contribution to fluorescence coming from the aromatic region. The abundance and characteristics of rainwater DOM was affected by season and storm origin. Marine storms contained a larger percentage of aromatic protons relative to the terrestrial storms. This coupled with lower spectral slopes and a higher percentage fluorescence in the C18 extract samples from marine storms suggests that while the dissolved organic carbon (DOC) concentrations in these storms are low, the DOM in marine storms likely contains recalcitrant DOM which is globally distributed. The composition of DOM in rainwater is also influenced by season. Samples collected during the warm season had lower spectral slopes and lower percent DOC in the reconstituted fraction which suggests that warm season storms contain smaller molecular weight DOM. This is a result of photodegredation during the warm season.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Keywords
Rain-water (Water-supply)--Analysis, Rain-water (Water-supply)--North Carolina--Wilmington, Water chemistry
Subjects
Rain-water (Water-supply) -- North Carolina -- Wilmington
Water chemistry
Rain-water (Water-supply) -- Analysis