Photochemically Induced Changes in Dissolved Organic Matter Identified by Ultrahigh Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
journal contributionposted on 01.02.2009, 00:00 by Michael Gonsior, Barrie M. Peake, William T. Cooper, David Podgorski, Juliana D’Andrilli, William J. Cooper
Sunlight-induced molecular changes have been observed in two samples of dissolved organic matter (DOM) collected in the Cape Fear River system, North Carolina, USA. The molecular composition of a water sample collected in the Black River (sample B210, salinity 0) and another water sample collected within the Cape Fear River estuary (sample M61, salinity 13.7) were analyzed using an ultrahigh resolution 9.4 Tesla (T) electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer. Additionally, the Ultraviolet/Visible (UV/vis) absorbance as well as the excitation emission matrix (EEM) fluorescence spectra were determined to identify changes in the optical properties associated with photochemical reactions of the chromophoric DOM (CDOM). The molecular formulas for the Cape Fear River Estuary (M61) sample before the irradiation experiments indicated the presence of highly aromatic compounds which were not present in the unirradiated Black River sample (B210). These aromatic compounds, with oxygen-subtracted double bond equivalents (DBE-O) values greater than nine, are more photoreactive and readily photodegraded relative to saturated compounds. Compounds with DBE-O values below nine are less photoreactive. The UV/vis absorbance and EEM fluorescence results supported this different photodegradation behavior, suggesting that the photoreactivity of CDOM is highly dependent on the molecular composition of the CDOM.
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compoundion cyclotron resonance mass spectrometerDissolved Organic Matter IdentifiedCDOMPhotochemically Induced Changesultrahigh resolution 9.4 Teslaexcitation emission matrixUVEEM fluorescence resultsDOMCape Fear River EstuaryCape Fear River estuarywater sampleUSAelectrospray ionization FourierCape Fear River systemunirradiated Black River sample