Soil Organic Matter Extraction Solvents

Organic solvents at STP and under supercritical conditions are the most common extractants for soil organic matter. Supercritical C02 and, to a lesser extent, N20 have also been used to extract both native and organic contamination from soil. Humus is extracted using aqueous solutions, but otherwise, water is rarely used to extract organic compounds from soil. A list of common soil organic matter extractants is given in Table 12.2. 

Coal, Soil Organic Matter and Other Related Materials. - 5.5.1 Coals and Carbonaceous Materials. C - The extract from carbon disulfide/AT-methyl-2-pyrrolidinone mixed solvent extraction of Upper Freeport coal at room temperature has been fractionated with acetone and pyridine into three fractions, and solid-state NMR measurements of these fractions have been measured. 

Humin is the portion of soil organic matter that remains as a residue after extraction of the soil with dilute alkali. This fraction is highly resistant to biotic breakdown and insoluble in alkali. This material is highly humified with carbon content >60%. Recent studies using NMR showed that humin contains significant amounts of paraffinic substances that are insoluble in alkali (Stevenson, 1994). Organic solvents used to extract soil lipids can potentially dissolve some component of humin. 

TINSLEY J. and SALAM A. 1961. Extraction of soil organic matter with aqueous solvents. Soils and Fertilizers, 24, 81-84. 

Yip [405] reported that the binding of the soil particles and organic matter with the herbicide residues prevented the complete extraction of them with an organic solvent. Upchurch and Mason [406] found that the extent of adsorption of herbicides is highly dependent on the type of organic matter and clay as well as on the amounts of their constituents. 

If a good deal of the organic protein (ossein) has been left in the bone, as is the case when the fat has been extracted by solvents, and not by steaming, the resulting bone-meal quickly decomposes in the soil, the phosphoric acid being made partly soluble by the decomposition products of the proteins. Such a bone-meal will contain (approximately) 45 per cent, of calcium phosphate, 1-5 per cent, of magnesium phosphate and over 30 per cent, of organic matter. 

It has for some time been a common practice to compare new extraction techniques with Soxhlet extraction, and ASE has been no exception in this respect. The ASE technique has many advantages over Soxhlet extraction, especially prominent among which are the following reduced operating times and consumption of organic solvents, and partial automatability. In many cases, ASE provides results similar to (e.g. in the extraction of organophosphorus pesticides, organic matter, hydrocarbons and PAHs from soil... 

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