Journal / Book Title
American Geophysical Union Fall Meeting, December 2010, San Francisco, CA.
The organic matter (OM) fraction of estuarine sediments is often distinctive and thus diagnostically useful in determinations of sedimentary provenance. Among the most fundamental distinctions to be made is that between terrestrial and aquatic OM. To supplement the parameters commonly used for this purpose (e.g., C/N and stable isotope ratios), we proposed the Vinylguaiacol/Indole or VGI ("Veggie") ratio, defined as [vinylguaiacol / (indole + vinylguaiacol)] using data produced by analytical pyrolysis-gas chromatography/mass spectrometry of dried, homogenized sediment samples. The ratio employs the peak areas of these two compounds on the mass chromatograms of their molecular ions (m/z 150 and 117). Major pyrolysis products of terrestrial plant lignin include a variety of methoxyphenols, notably 4-vinylguaiacol. In contrast, aquatic algae and bacteria characteristically produce distinctive organonitrogen compounds upon pyrolysis, particularly indole, derived from the amino acid tryptophan. The end member VGI ratio value of 1.00 is obtained for reference land plant matter, including the marsh plants Phragmites and Spartina, as well as maple and pine wood. The end member value of 0.00 is obtained for cultured microbes, including Escherichia coli and the cyanobacterium Anacystis. Vinylguaiacol and indole are commonly detected in Recent sediment pyrolyzates. We hypothesized that their relative quantities therein should be proportional to the relative contributions of land plant and microbial OM, respectively.
Samples taken from Spartina peat marshes at the mouths of major rivers (Housatonic and Connecticut) entering Long Island Sound, wetlands behind the barrier island at Cape May (NJ), and a Phragmites-dominated tidal marsh along the Hackensack River (NJ) have high (> 0.8) VGI ratio values. Sediments collected within the Newark Bay (NJ) estuary from the lower Passaic and Hackensack Rivers and the Arthur Kill show mixed terrestrial and aquatic OM signatures (VGI from 0.3 to 0.7, generally increasing upstream). Jamaica Bay (NY), behind an Atlantic barrier island and with marsh islands and multiple urbanized tidal creeks, displays a very wide VGI range, affected by proximity to stands of marsh vegetation, bathymetry, and sediment grain size. Sediments from New Haven (CT) harbor show a diminution in VGI values from 0.66 at the mouth of the Quinnipiac River to 0.08 at the entrance to the harbor over a distance of only 4 km, as terrestrial influences wane moving towards open water. Deep water Long Island Sound sediments show a strong predominance of aquatic OM (VGI about 0.05), while nearshore sediments collected 2 km from the mouth of the Housatonic River and in embayments near the Connecticut and Thames River mouths have a greater terrestrial OM component (VGI of 0.15 to 0.23). The results demonstrate a precipitous decrease in the relative amounts of unaltered land plant OM in the offshore direction, but also that a minor fraction persists in deeper water environments.
MSU Digital Commons Citation
Kruge, Michael A.; Olsen, Kevin K.; Slusarczyk, Jaroslaw W.; and Gomez, Elaine, "The Vinylguaiacol/Indole or VGI ("Veggie") Ratio: A Novel Molecular Parameter to Evaluate the Relative Contributions of Terrestrial and Aquatic Organic Matter to Sediments." (2010). Department of Earth and Environmental Studies Faculty Scholarship and Creative Works. 78.
Kruge M.A., Olsen K.K., Slusarczyk J., Gomez E., 2010, The Vinylguaiacol/Indole or VGI ("Veggie") Ratio: A Novel Molecular Parameter to Evaluate the Relative Contributions of Terrestrial and Aquatic Organic Matter to Sediments. American Geophysical Union Fall Meeting, December 2010, San Francisco, CA, Paper No. OS31B-1428