Organic matter associations

Previously, it was noted that organic matter associated with the coarse fraction of a sorbent was a substantially weaker sorbent than the organic matter associated with smaller materials (15). 

Carter, P.W., and R.M. Mitterer. 1978. Amino acid composition of organic matter associated with carbonate and non-carbonate sediments. Geochimica et Cosmochima Acta 58 1231-1238. 

Jacques Jedwab. We have not identified the minerals ourselves. However, extensive lists of minerals showing uranium organic matter associations have been published as follows ... 

Although adequate information is available from rivers of the temperate regions, they are very scarce for those of tropical rivers. Data reviewed by Milliman and Meade (1983) show that about 70 % of the total sediment discharge to the oceans occur via the Southeast Asian rivers (Fig. lt). Inclusion of sediment data and the organic matter associated with these sediments might change drastically the net POC transport from land to sea. 

S.U. Khan, Organic matter association with soluble salts in the water extract of a black solonetz soil, Soil Sci. 109 (1970) 227-228. 

Mikutta, R., Kleber, M.,Torn, M. S., and Jahn, R. (2006). Stabilization of soil organic matter association with minerals or chemical recalcitrance Biogeochem. 77, 25-56. 

Deposit feeders benthic organisms that ingest and extract the organic matter associated with sedimentary particles for their nutrition. 

Canuel, E.A., and Martens, C.S. (1993) Seasonal variation in the sources and alteration of organic matter associated with recently-deposited sediments. Org. Geochem. 20, 563-577. 

Pokrovdd O. S. and Schott J. (2002) Iron colloids/organic matter associated transport of major and trace elements in small boreal rivers and their estuaries (NW Russia). Chem. Geol. 190, 141-181. 

Puget P., Chenu C., and Balesdent J. (2000) Dynamics of soil organic matter associated with particle-size fractions of water-stable aggregates. Euro. J. Soil Sci. 51(4), 595-605. 

Sorption of VOCs involves the processes of adsorption and partitioning. Partitioning is the incorporation of the VOC into the natural organic matter associated with the solid and is analogous to the dissolution of an organic compound into an organic solvent. Adsorption is the formation of a chemical or physical bond between the VOC and the mineral surface of a solid particle (Rathbun, 1998). The equilibrium relation between aqueous and solid phase concentrations then is expressed as... 

NMR and FTIR results indicate that both the organic matter associated with carbonate minerals and that associated with silicate minerals is predominantly of paraffinic composition. In addition, both groups contain approximately equal relative concentrations of aromatic structures. The latter result is in disagreement with Spiro s (2) data which indicate that the organic matter associated with silicates contains more aromatic as well as more polar structures as compared with the organics associated with carbonate minerals. This apparent difference in aromatic... 

In any particular system, some limited subset of these interactions is likely to dominate overall sorption behavior. In saturated subsurface systems, for example, most natural solid phases have only a weak affinity for hydrophobic organic compounds. It is frequently presumed for such systems that the characterization of one major sorption reaction, such as that between organic contaminants and natural organic matter associated with soils, sufficiently characterizes the overall process. Such an approach may be problematic for circumstances in which limited characterizations developed from one set of observations are extended to different system conditions, including different contaminant concentration ranges. 

Deviations from organic carbon correlations at these Iow/qc values have been attributed to sorption at mineral surfaces (6, 9). Furthermore, the reliability of K(l( predictions at higher/oc values may be affected by differences in sorption behavior attributed to differences in the organic matter associated with different types of natural. solid phases and, potentially, with different fractions of any particular natural sorbent (3, 10, 11). 

However, the Cs value for HOCs is controlled most by the adsorption onto (and/or absorption into) natural organic matter associated with the solid phase. 

For the lOMD model, the primary assumption is that sorbent organic matter is a polymeric-type substance within which sorbate can diffuse. The organic matter associated with natural sorbents has been reported to be a flexible, cross-linked, branched, amorphous (noncrystalline), polyelectrolytic polymeric substance (Choudhry, 1983 Hamaker and Thompson, 1972 Hayes and Swift, 1978 Schnitzer, 1978 Stevenson, 1982 Wershaw, 1986). Direct confirmation of the porous nature of organic matter has been reported (Degens and Mopper, 1976 Schnitzer, 1978). 

---