Humification

The macerals in lower rank coals, eg, lignite and subbiturninous coal, are more complex and have been given a special classification. The term huminite has been appUed to the macerals derived from the humification of lignocellulosic tissues. Huminite is the precursor to the vitrinite observed in... 

Studies on the Fractionation of Humification Products of Ryegrass on Sand Columns, M. H. B. Hayes, M. Stacey, and J. Standley, Geoderma, 7 (1972) 105-111. 

Dec J, KL Shuttleworth, J-M Bollag (1990) Microbial release of 2,4-dichlorophenol bound to humic acid or incorporated during humification. J Environ Qual 19 546-551. 

Organic acid fluorescence. In a similar manner to trace constituents, such as Mg, Sr and P, concentrations of organic acids present in speleothem calcite are sufficient to observe variation at temporal scales of less than annual in some cases (e.g.. Baker et al. 1993, Shopov et al. 1994). Organic acids (humic and fulvic) are formed in the soil by humification, and transported to the cave void by percolating waters where they are entrapped in precipitating carbonates. Under certain circumstances, where precipitation patterns are strongly seasonal and the nature of vadose percolation is such that seasonal mixing is incomplete, bands with different luminescent intensities can be differentiated after excitation with UV radiation. In other cases, bands are not observable but secular... 

Baker A, Genty D, Smart PL (1998) High-resolution records of soil humification and paleochmatic change from variations in speleothem luminescence excitation and emission wavelengths. Geology 26 903-906 Baker A, Ito E, Smart PL, McEwan R (1997) Elevated C in speleothem and imphcations for palaeo-vegetation studies. Chem Geol 136 263-270... 

Johnson KJ, Cygan RT, Fein JB (2006) Molecular simulations of metal adsorption to bacteria surfaces. Geochim Cosmochim Acta 70 5075-5088 Jokic A, Frenkel AI, Vairavamurthy MA, Huang PM (2001) Bimessite catalysis of the Maillard reaction and its significance in natural humification. Geophys Res Lett 28 3899-3902... 

Krishnamurti GSR, Wang MK, Huang PM (2004) Effects of pyrollogol on Al13 tridecamer formation and humification. Clays Clay Miner 52 734-741 Kumada K, Kato H (1970) Browning of pyrogallol as catalyzed by clay minerals. Soil Sci Plant Nutr 16 195-200... 

The determination of the methoxy group (OCH ) content of soils is important in studies concerned with the degree of humification of soil organic matter. Methods used to determine methoxy groups in soils have generally been based on volumetric modifications of the classical Zeisel method, which is a complicated and tedious procedure requiring specialised apparatus. 

The interest in mineral-promoted organic reactions stems from the need to understand the fate of pesticides in soils and pollutants in sedimentary environments (8), petrogenesis (20-27), humification (19, 28, 29), the origin and evolution of life (1, 30), the use of clays as catalysts in industrial processes (31-37), in pharmaceutical applications (3), and as pigments and fillers in paper, plastic, and rubber (37). 

Drzyzga et al. [411] conducted experiments to evaluate the levels of incorporation and transformation of TNT and metabolites into the organic soil matrix of anaerobic and sequential anaerobic-aerobic treated soil/molasses mixtures. They proposed a two-step treatment process (i.e., anaerobic-aerobic bioremediation process) with some special procedures during the anaerobic and the aerobic treatment phases. The transformation of TNT at the end of the experiments was above 95% and 97% after anaerobic and sequential anaerobic-aerobic treatment, respectively. This technique is considered the most promising method for effective, economic, and ecologically acceptable disposal of TNT from contaminated soils by means of immobilization (e.g., humification) of this xenobiotic. 

The basic structure of humic substances involves a backbone composed of alkyl or aromatic units crosslinked mainly by oxygen and nitrogen groups. Major functional groups attached to the backbone are carboxylic acids, phenolic hydroxyls, alcoholic hydroxyls, ketones, and quinones. The molecular structure is variable as it is dependent on the collection of DOM available in seawater to undergo the various polymerization, condensation, and oxidation reactions and reaction conditions involved in humification, as well as the ambient physicochemical reaction conditions, such as temperature and light availability. 

Labile and refractory DOM undergo abiotic photochemical reactions in the photic zone, especially in the sea surfece microlayer where physical processes concentrate DOM into thin films. Some of these reactions appear to be important in the formation of refractory DOM and others in its degradation. For example, DOM exuded by diatoms during plankton blooms has been observed to be transformed into humic substances within days of release into surfece seawater. Laboratory experiments conducted in seawater have demonstrated that photolysis of labile LMW DOM promotes the chemical reactions involved in humification and produces chemical structures foimd in marine humic substances. 

Physically protected organic matter ( abiotic condensation or humification) T... 

Humification The formation of humic substances via abioUc reacUons, including condensations and... 

Both and nmR showed the presence of aromatic and aliphatic components. In l C-NMR, resonances at =58 ppm indicate the presence of many OCH3 groups, such as those occurring in syringic, vanillic, and ferulic acids. Spectra clearly show the presence of palmitic and stearic acids by GC/MS, IR, and NMR data. The fulvic and humic acids are predominantly made up of phenolic and fatty acid units. These are highly aromatic because lignin residues have been incorporated in the humification process. 

Iron oxides promote the oxidation of phenols, a process of importance during the humification of biomass in nature, particularly in soils (Scheffer et al., 1959 Wang et al., 1986). In slightly acid solutions in the presence of finely divided goethite, hy-droquinone molecules are converted to quinone (Shido and Huang, 1984). Consumption of O2 in solution is promoted suggesting that the iron oxide had a catalytic... 

Quring humification various plant constituents decompose at different rates. 

We have investigated the humification of straw, as an example, under constant conditions of humidity and temperature in a climatic chamber (4,18) and separated different fractions according to a modified method of Waksman s proximate analysis. The amount of nitrogen present in these processes is the factor limiting the rate of decomposition. Therefore we added nitrogen in form of ammonium nitrate in a quantity of 1% of straw dry weight to a nutrient solution in one experiment while the nutrient solution had no nitrogen in a parallel experiment. Table I shows the calculated data. 

The various observations and conclusions are summarized in Figure 6 where a complete scheme for lignin decomposition is proposed. It has some interesting implications for the process of humification. As Figure 6 shows, the following steps occur in the decomposition of lignin ... 

In the case of humification, nitrogen compounds react to a different extent in these stages of the reactions when aromatic components are involved. The extent of nitrogen fixation depends on die available o-amino nitrogen compounds and the environmental conditions (9). In the case of natural humification, the biological processes can be considered more or less finished at this stage. 

For practical purposes, the properties of humid air are recorded on psychrometric (or humidity) charts such as those of Figures 9.1 and 9.2, but tabulated data and equations also are available for greater accuracy. A computer version is available (Wiley Professional Software, Wiley, New York). The terminal properties of a particular adiabatic humification of air are located... 

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