Abstract
Less than twenty-five percent of the dissolved organic matter (DOM) isolated from the Mississippi River delta and Gulf of Mexico was characterized as carbohydrates, protein or fatty acid. The remaining seventy-five percent contained polar-substituted aromatic compounds, possibly polyhydroxyphenols or polyhydroxybenzoic acids, and non-polar aliphatic compounds as indicated by infrared and nuclear magnetic resonance spectroscopy. Volatile components detected by gas chromatography may include sterols, tocopherols and fatty alcohols. Differences in DOM from the Mississippi River delta and DOM from surface Gulf of Mexico water were greater than between DOM from surface and 2000 m water in the eastern Gulf of Mexico. Mississippi River DOM had a lower carbon:nitrogen ratio (8.8) than surface Gulf of Mexico water (30.0). The DOM from 2000 m had a C/N ratio of 29.6. Total fatty acid analysis revealed that the Mississippi River contained fewer individual acids (8) than did either surface Gulf of Mexico (20) or 2000 m Gulf of Mexico DOM (18). A greater relative infrared absorbance due to polar-substituted aromatic compounds was present in the river than in the Gulf of Mexico. A moderately high molecular weight fraction (5000 - 10,000 molecular weight) was more abundant in the river than in the Gulf of Mexico. A subfractionation procedure using silicic acid column chromatography further delineated the differences between Mississippi River dissolved organic matter and oceanic dissolved organic matter. This procedure made possible gas chromatography, infrared and nuclear magnetic resonance spectroscopy and CHN analysis of the subfractions which further characterized the organic matter in sea water. Modifications of the Lowry protein method are described which correct for interferences due to phenolic-like compounds in natural waters.
Rankin, John Graham (1974). Chemical and physical characteristics of dissolved organic matter isolated from the Mississippi River delta and Gulf of Mexico. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -172602.