Water refractory organic substances

Schulten, H.-R., Leinweber, R, and Jandl, G. (2002). Analytical pyrolysis of humic substances and dissolved organic matter in water. In Refractory Organic Substances (ROS) in the Environment, Frimmel, F. H., Abbt-Braun, G., Heumann, K. G., Hock, B., Ludemann, H.-D., and Spiteller, M., eds., Wiley-VCH, Weinheim, pp. 163-187. 

Hesse S, Kleiser G, Frimmel FH (1999) Characteri2ation of Refractory Organic Substances (ROS) in Water Treatment, Water Sci. Technol. 40, No. 9 1-7. 

Synchronically, new forms of OM are synthesised by bacteria. The combined processes lead to the formation of the refractory organic substance — water humus — in particulate and dissolved state. This surely occurred initially in the Precambrian period with blue-green algae and bacteria in water reservoirs under anoxic conditions (Rutten, 1971). As shown by experiments, the degree of decomposition of the OM of dead hydrobionts under such conditions was less. That is why more organic residues settled on the bottom of the reservoir. Naturally this influenced the further transformation of OM in sediments and the accumulation of oil precursors their concentration in the anaerobic conditions of the Precambrian must have been... 

Most organic substances can be dissolved readily in a suitable organic solvent and some are directly soluble in water or can be dissolved in aqueous solutions of acids (basic materials) or of alkalis (acidic materials). Many inorganic substances can be dissolved directly in water or in dilute acids, but materials such as minerals, refractories, and alloys must usually be treated with a variety of reagents in order to discover a suitable solvent in such cases the preliminary qualitative analysis will have revealed the best procedure to adopt. Each case must be considered on its merits no attempt at generalisation will therefore be made. It is however of value to discuss the experimental technique of the simple process of solution of a sample in water or in acids, and also the method of treatment of insoluble substances. 

Hubberten, U., Lara, R.., and Kattner, G. (1995). Refractory organic compounds in polar waters Relationship between humic substances and amino acids in the Arctic and Antarctic. Journal of Marine Research 53(1), 137-149. 

The indophenol method has been applied for determination of nitrogen (as ammonia) in biological materials [31,32], plant materials [33,34], foods [1,2,35], air [36], boiler water [37], and other waters [38-40], organic substances [17,41], refractory alloys [42], tantalum alloys [43], vanadium, titanium, and uranium [21], alkali and alkaline earth metals [22],... 

The used clay (12% in weight) was a German refractory one with 41% AI2O3, which is widely used in such products. Due to the fact that the raw material clay contains crystal water (for example, in kaolinite) and organic substances, which... 

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial role in many biogeochemical processes. 

Many three-dimensional polymeric substances are particularly refractory, insoluble and unreactive. One- and two-dimensional polymers tend to be more soluble. For example, dichlorides and trichlorides of the 3d elements are generally quite soluble in weakly-polar organic solvents such as alcohols, ethers and ketones. The driving force here is the formation of complexes with the solvent molecules. These compounds are also soluble in water, with some degree of hydrolysis. Aluminium(III) chloride (which has a layer structure similar to that of CrCl3) dissolves in some non polar organic solvents, such as benzene, in which it forms A12C16 dimers. 

Black C, produced by wild fires and humic substances (HS), the natural by products of SOM decomposition in soil and water systems, are certainly the classes of organic compounds that most closely approximate this recalcitrant behavior. HS occur widely, being found in large amounts not only in the soil and sediments but also in lakes, rivers, ground waters, and even the open ocean (Stevenson, 1994). Besides these relatively refractory substances, more labile compounds can persist in soil for a much longer time than would be predicted from their inherent recalcitrance to decomposition. SOM stabilization (Figure 5.2) is generally considered to occur by three main mechanisms (i) physical protection, (ii) chemical stabilization, and (iii) biochemical stabilization (Six et al., 2002). 

While specific compounds such as siderophores have been found in natural waters, the bulk of the dissolved organic matter (DOM) is made up of relatively refractory compounds known as humic substances. These substances exhibit complex, ill-defined structures with the actual structure depending markedly on the source of the organic material. DOM in the open ocean is almost entirely authochthonous and formed by condensation, polymerisation and partial oxidation of smaller molecules such as triglycerides, sugars and amino acids and exhibits very little aromatic character [78]. In contrast, the DOM in fresh and coastal waters is largely allochthonous and derived... 

Refractoriness The resistance of a substance to degradation. Often applied to organic matter Relative humidity The ratio of the partial pressure of water to the saturation vapor pressure at that temperature Reservoir An amount of material defined by certain chemical, physical, or biological characteristics that, under particular conditions, can be considered as reasonably homogeneous... 

Apparently, the particulate organic matter is oxidized, even in deep waters, but at a very slow rate. This modification of organic matter tends to the formation of very inert substances, more aliphatic molecules, refractory to further decomposition. The organic matter first loses nitrogen, phosphorus and oxygen since the activation energies for cleav e of the C—C and C—H bonds are several kcal mole" higher than those of the C—N, C—P or C—O bonds (Toth and Lerman, 1977). 

They constitute 75% w/w of the organic matter in most soils and 50% of the organic carbon in surface waters. Humic substances are composed of complex heterogeneous mixtures of organic compounds and are characterized as being yellow to brown in color, of high relative molecular mass, and refractory. Unlike many other natural organic products, they cannot be described in terms of unique chemical structures and are operationally defined by the technique used for their extraction and fractionation. 

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