Organic Matter in Aquatic Environments

All natural waters contain some carbonaceous material. Even rainwater has been shown to include about 1 mg C/L (Thurman, 1985). Some of this organic material is in the form of truly dissolved, soluble compounds, whereas other fractions consist of colloidal or particulate organic matter. The definitions of dissolved and particulate carbon that have been more or less established by convention among aquatic scientists are somewhat elastic and arbitrary one criterion that is widely used sets the boundary between the two at 0.45 /tM (the pore size of some common filter media). These demarcations tend to disguise the fact that there is a continuum of organic particles in water that ranges in relative size from molecules to microorganisms. 

Small molecules. Although the bulk of the DOC in practically all natural surface waters is polymeric, approximately 10% or so consists of small, identifiable compounds. It is probable that in the open ocean the excretion of cellular metabolites from living and dead planktonic animals, plants, and bacteria whose home is the ocean contributes the great majority ( 99%) of dissolved organic matter nearer to shore, or in landlocked bodies of water, sources that are land-derived (soil, leachates of land plants, etc.) become more predominant. 

Carbonyl compounds, carboxylic acids, and esters of a wide variety of types have been isolated from surface waters. Aldehydes and ketones are produced during the photolysis of larger polymers such as humic materials formaldehyde, acetaldehyde, and glyoxal appear to be the most abundant in seawater samples (Kleber and Mopper, 1990). Low molecular weight mono-, di-, and tricarboxylic acids such as acetic, formic, lactic, glycolic, malic, and citric acids have been reported by many investiga- 

Hydrocarbons may enter the aquatic environment via de novo synthesis, accidental oil spillages, runoff from the land, leaching from sediments, or atmospheric fallout. Concentrations of total hydrocarbons in marine surface waters vary from 

1 to 75 /tg/L, with the majority of samples from unpolluted environments having values toward the lower end of the range. Alkanes (branched, cyclic, and linear), as well as many aromatic compounds, commonly occur (Zsolnay, 1977). 

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DOM is composed of small molecules that can be obtained by filtration. Quantification of organic matter in aquatic environment is performed by measuring the concentrations expressed in organic carbon. One measures total organic carbon (TOC) obtained from raw liquid sample, particulate organic carbon (POC) by analyzing the filter, and the dissolved organic carbon (DOC) characterized from the sample after filtration. 

Stedmon, C.A., Markager, S., and Bro, R. (2003). Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy. Mar. Chem., 82,239-254. 

Biological Origins and Fate of Fluorescent Dissolved Organic Matter in Aquatic Environments... 

Williams, P. M. (1971). The distribution and cycling of organic matter in the ocean. In "Organic Compounds in Aquatic Environments" (S. D. Faust and J. W. Hunter, eds). Dekker, New York. 

Hassett, J. P. and Anderson, M. (1979). Association of hydrophobic organic compounds with dissolved organic matter in aquatic systems. Environ. Sci. Technol. 13, 1526-1629. 

M. Schnitzer, "Metal-Organic Matter Interactions in Soils and Waters," in Organic Compounds in Aquatic Environments, S. D. Faust, and J. V. Hunter, eds. Dekker, New York, 1971, p. 297. 

Schnitzer M (1971) Metal-organic matter interactions in soils and waters. In Faust SD, Hunter JV (eds) Organic compounds in aquatic environments. Dekker, New York, pp 297-315... 

Humic acids (HA) and fulvic acids (FA) are the main components of humic substances (HS), which are the most chemically and biochemically active and widely spread fractions of nonliving natural organic matter in all terrestrial and aquatic environments. They comprise a chemically and physically heterogeneous group of substances with colloidal, polydis-persed, polyelectrolyte characteristics and mixed aliphatic and aromatic nature (Senesi and Loffredo 1999). 

Watt BE, Clark NWE, Hayes MHB, Chipman JK, Skjemstad JO, Swift RS (1996) Aquatic humic substances from Pristine watersheds chemistry and postchlorination mutagenicity. In Clapp CE, Hayes MHB, Senesi N, Griffith SM (eds) Humic substances and organic matter in soil and water environments characterization, transformations and interactions. Proceedings of the 7th international conference IHSS, St. Augustine, Trinidad and Tobago, pp 389-390... 

Buffle, J. (1984). Natural organic matter and metal-organic interactions in aquatic systems. In Metal Ions in Biological Systems. Vol. 18, Circulation of Metals in the Environment, ed. Sigel, H., Marcel Dekker, New York, pp. 165-221. 

Weber, J.B. Interaction of organic pesticides with particulate matter in aquatic and soil systems, in Fate of Organic Pesticides in the Aquatic Environment, Advances in Chemistry Series, Gould, R.F., Ed. (Washington, DC American Chemical Society, 1972), pp. 55-120. 

Gobas, F.A.P.C. and X. Zhang. 1994. Interactions of Organic Chemicals with Organic Matter in the Aquatic Environment. In Environ. Toxicol. Chem. Special Publication, "Bioavailability Physical, Chemical and Biological Interactions, J.L. Hamelink, Peter F. Landrum, Harold L. Bergman, and W.H. Benson, Eds., pp. 83-91, Lewis Publishers, Chelsea, MI. 

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