Marine Colloidal Organic Matter

Isolated from Gulf of Mexico surface waters. 

3 Suspended Particulate Matter erom River Mersey in NW England 

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Fig. 7-13. Comparison of Th(IV) binding to whole marine colloidal organic matter and the acid polysaccharide fraction (data from Murphy, 2000). The data are plotted in the form of a classic Schubert plot (Schubert, 1948). The analytical method is a ligand competition, liquid-liquid extraction technique using HDEHP (di-2-ethylhexyl phosphoric acid) in toluene to compete against the colloidal organic matter (COM) in an aqueous phase. Xq is the toluene/aqueous phase distribution of the Th in the absence of the COM X is the partitioning in the presence of the COM.

Murphy, R.J. 2000. Thorium (IV) binding to oiganic and inorganic ligands Marine colloidal organic matter, marine polysaccharides and hematite. Environ. Sci. Eng. Div., Colorado School of Mines, Golden. 

Brownawell, B.J. The role of colloid organic matter in the marine geochemistiy of PCBs, Ph.D. Dissertation, Woods Hole-MIT Joint Program. Cambridge, MA. 1986. 

Chin, Y. P., and P. M. Gschwend. 1992. Partitioning of PAHs between porewater colloidal organic matter and marine interstitial waters. Environmental Science and Technology 26 1621. 

Guo, L., Santschi, P.H., and Warnken, K.W. (2000a) Trace metal composition of colloidal organic matter in marine environments. Mar. Chem. 70, 257-275. 

Wells, M.L. (2002) Marine colloids and trace metals. In Biogeochemistry of Marine Dissolved Organic Matter (Elansell, D.A., and Carlson, C.A., eds.), pp. 367-397, Academic Press, New York. 

There is also some evidence to suggest that the colloidal material in estuaries is dominated by marine-derived organic matter rather than that of terrigenous origin (Sigleo et al. 1982 Zsolnay, 1979). However, it is unclear whether this trend is due to loss of terrigenous material because of aggrega-... 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Chemical analyses of marine organic matter usually starts with a segregation into the solid, dissolved, or colloidal phase. As described in Chapter 3.2, this segregation often... 

Boehme, J., and Wells, M. (2006). Fluorescence variability of marine and terrestrial colloids Examining size fractions of chromophoric dissolved organic matter in the Damariscotta River estuary. Mar. Chem. 101, 95-103. 

HMW biopolymers are part of the colloid-sized fraction of marine organic matter that can be visualized and enumerated with transmission electron microscopy (TEM) (Wells and Goldberg, 1991, 1993). Colloids range in size from a few nanometers up to 1 p,m in size. Very small colloids (<30 nm) are irregular in shape, while larger colloids (—30-60 nm) are more spherical assemblies of 2-5 nm sized subparticles. Concentrations of small colloids (<200 nm) range from nondetectable (<10" colloids ml ) to... 

A variety of spectroscopic techniques have been applied to DOC isolated from seawater by cross-flow ultrafiltration or adsorption onto XAD resins. The two techniques isolate very different organic fractions from seawater. Hydrophobic fractions (such as marine humic material) are isolated on XAD resins [48], whereas the organic matter extracted by ultrafiltration is retained primarily on the basis of its molecular size and shape [49], resulting in isolates rich in nitrogen and carbohydrates (polysaccharides). Nuclear magnetic resonance (NMR) spectroscopy has proven successful in distinguishing between the specific structures of XAD-bound humics and the carbohydrates concentrated into colloidal size fractions. 

By reviewing microscopic observations, physicochemical properties and numerical simulations of colloid dynamics, BufQe et al. [24] have developed a three-component picture of the heteroaggregation of colloids. In marine systems the three components are inorganic colloids (IC), refractory organic matter (ROM) with characteristics similar to freshwater fulvic material, and fibrillar polymers (FP). 

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