Impact of sediment resuspension and photochemistry on dissolved organic carbon and copper speciation
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Michelle Leigh Smith (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Stephen Skrabal
Abstract: Changes in dissolved organic carbon (DOC) and Cu speciation caused by
sediment resuspension and photochemistry in the highly turbid, organic rich waters of the
Cape Fear River Estuary (CFRE) have been investigated. The concentration of DOC in
filtered estuarine samples exposed to simulated sunlight decreased 4 -27 mM compared
with dark controls which also decreased but to a lesser extent. This indicated that organic
carbon was being converted to inorganic carbon in light exposed samples and consumed
in dark controls. Unfiltered irradiated samples containing ambient river particles
experienced an increase in DOC relative to samples with no particles, indicating particles
are capable of producing DOC upon exposure to light. When suspended sediments (2 g
wet sediment per L) were present, 3-145 mM DOC was released in light exposed samples
relative to dark controls. The DOC released was directly related to the percent organic
carbon in the sediment. When resuspended sediment samples were exposed to
photosynthetically available radiation (PAR) rather than full spectrum light, there was
significantly less DOC produced suggesting UVA/UVB light is the most effective at
engendering changes in DOC.
A series of photolysis experiments were also conducted to determine the effects of
irradiation and resuspended sediments on total dissolved copper (TDCu) concentrations.
In relatively uncontaminated environments, there was little or no effect of sediments or
irradiation on TDCu levels in the estuary. In more contaminated environments, such as
seen in San Diego Bay and the Port of Wilmington in the CFRE, there was a significant
increase in TDCu production after irradiation in 0.2 mM filtered water containing
sediments. These results suggest that the impact of sediment resuspension on TDCu concentration depends to a large extent on how much Cu is present in the irradiated
sediments.
In addition to TDCu, the impact of light exposure and sediments on Cu(I) was
also investigated. Copper(I) concentrations in filtered CFRE water increased in light
exposed samples suggesting production of reduced Cu from other dissolved Cu species.
Little impact of ambient particles or sediments on Cu(I) concentrations were observed.
The effect of full spectrum and PAR on the photodegradation of strong Cu binding
ligands was also studied in filtered water with no added sediments. When exposed to full
spectrum light, ligand concentrations decreased from 55 nM to 10 nM, whereas samples
exposed only to PAR decreased from 50 nM to 19 nM, indicating that PAR is very
effective at the degradation of Cu ligands in the water column.
Impact of sediment resuspension and photochemistry on dissolved organic carbon and copper speciation
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina in Partial Fulfillment Of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Carbon--Speciation, Copper--Speciation, Photochemistry, Sedimentation and deposition--North Carolina--Cape Fear River Estuary
- Subjects
- Copper -- Speciation
- Carbon -- Speciation
- Photochemistry
- Sedimentation and deposition -- North Carolina -- Cape Fear River Estuary