Dissolved organic matter stabilization

Gasper. J.D., Aiken, G.R., and Ryan, J.N. (2007). A critical review of three methods used for the measurement of mercury (Hg+ ) dissolved organic matter stability constants. Appl. Geochem., 22,1583-1597. 

Kalbitz, K., Schwesig, D., Rethemeyer, J., and Matzner, E. (2005). Stabilization of dissolved organic matter by sorption to the mineral soil. Soil Biol. Biochem. 37,1319-1331. 

Wetzel, R.G (2003) Dissolved organic carbon detrital energetics. Metabolic regulators, and drivers of ecosystem stability of aquatic ecosystems. In Aquatic Ecosystems Interactivity of Dissolved Organic Matter (Findlay, S.E.G, and Sinsabaugh, R.L., eds.), pp. 455 175, Academic Press, New York. 

Chemical Speciation Models. Using the stability constants derived by us for copper complexes with hydroxo and carbonate ligands (Table I) and for natural organic ligands (Table II), the Newport and Neuse Rivers were modeled for copper speciation as a function of pH, total copper, carbonate alkalinity and total dissolved organic matter. Speciation models were calculated from the equation ... 

SOM is composed of a continuum of organic resources from fresh plant residues to stabilized organic matter (OM) or humus (Stevenson, 1994). Although this definition of SOM includes intact plant litter, in this review we will often distinguish between decomposition of litter on the soil surface and decomposition/stabilization of OM within the mineral soil. Within the mineral soil, SOM is often divided into four categories the light fraction, microbial biomass (discussed above), dissolved organic matter (DOM), and stable humic substances. 

Dissolved organic matter, expressed as chemical oxygen demand (COD) or total organic carbon (TOC), including methane, volatile fatty acids (in particular in the acid phase of the waste stabilization Christensen and Kjeldsen (1989), and more refractory compounds, e.g., fulvic-like and humic-like compounds. 

At low concentrations of dissolved organic matter (DOM) (<0.01 mg of C/L) and at low ionic strength (10-3 M), the hematite particles are positively charged at this pH and are stabilized electrostatically by interacting diffuse layers with characteristic (Debye) lengths of 10 nm. As the ionic strength is increased to 10 1 M at these low DOM concentrations, the diffuse layers are compressed to 1 nm, and attractive van der Waals forces promote attachment in classical Derjaguin-Landau-Verwey-Overbeek (DLVO) destabilization by what has been termed double-layer compression. 

Few studies report actual measurement of Cd + speciation in soil solutions. Many authors report Cd speciation based on the measured total dissolved Cd concentration and computation of free Cd using chemical equilibrium models. The accuracy of the speciation depends on the correctness of Cd-complex stability constants (Turner, 1995). For example, the proportion of free Cd (as Cd ) in solution varies from 16 to 82% depending on the log K values for Cd-(DOM) dissolved organic matter complexes (Table 4). The stability constants of Cd-humics are particularly uncertain. The reported high values of pCd + ranged... 

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