Humic substances sulfur

Organic forms of carbon, nitrogen, sulfur, and phosphorus (typically less than 0.7 pm in diameter) contribute to bulk DOM. Humic substances,... 

A beneficial effect of humic substances on the nutrient uptake and contents of plants has been reported for the major inorganic elements, such as nitrogen, phosphorus, potassium (Mylonas and McCants, 1980), and sulfur (Guminski, 1968). In addition, the uptake and contents of nutrients such as calcium, magnesium (Mylonas and McCants, 1980), sodium (Vaughan and McDonald, 1976) and copper (Rauthan and Schnitzer, 1981) are also enhanced by humic substances. Most of these reports on the effects of HS on the nutrient contents of plants are purely descriptive, and little attempt has been made to elucidate the mechanisms of the action of the humic material. The authors proposed both an indirect and a direct effect of HS on plant nutrition. In the former case HS may, for example, chelate a cation, thus changing... 

Extraction of humic substances has been a useful way of characterizing NOM properties by NEXAFS. In those cases where the element studied also has significant inorganic fractions such as sulfur in submerged soils and sediments, or phosphorus in most mineral soils and sediments, an extract appears to be the only approach to obtain meaningful information about NOM. Often, it was found that the spectra have a lower background and can be more easily analyzed quantitatively... 

Vairavamurthy, A., Maletic, D., Wang, S., Manowitz, B., Eglinton, T., and Lyons, T. (1997). Characterization of sulfur-containing functional groups in sedimentary humic substances by X-ray absorption near-edge spectroscopy. Energy Fuels 11,546-553. 

Ferdelman T. G., Church T. M., and Luther G. W., Ill (1991) Sulfur enrichment of humic substances in a Delaware salt marsh sediment core. Geochim. Cosmochim. Acta 55(4), 979-988. 

Nutrient— Any chemical required for life. The most important nutrients that plants obtain from soil are compounds of nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Organic matter— Any biomass of plants or animals, living or dead. The most important form of organic matter in soil is dead, occurring as humic substances. 

Humic substances in peatlands are often hypothesized to be precursors in the formation of coal. In Table 2 the elemental analyses of several Canadian peats are compared with those of different coals. The data on peats show that the carbon, sulfur, and nitrogen contents increase with increasing degree of decomposition and the oxygen content decreases. The sulfur con-... 

A useful procedure for the isolation of humic substances from groundwater is that of Thurman and Malcolm (1981) with the following modifications. Hydrochloric acid should be added immediately to the water sample to prevent the precipitation of iron hydroxide, and the sample should be evacuated with a vacuum pump to remove hydrogen sulfide. If the sulfide is not removed, it can react to form both elemental sulfur and polysulfides that adsorb onto and clog the XAD resin (Leenheer and Noyes, in press Thurman, 1979). 

The carbohydrate content of humic substances from groundwater was determined by the Mollisch test (Clapp, 1969) on all samples. In this assay, polysaccharides within the humic material are hydrolyzed with sulfuric acid into monomers that are then determined by a colorimetric test. 

Variations in the atomic S/C ratios are more difficult to observe because of experimental uncertainties linked to the determination of organic sulfur. In surface sediments, S/C ratios are within the range 0.01-0.03 and generally decrease from fulvic acids to humic acids to stable residues. In stable residues, sulfur content increases rapidly in the few first meters of burial (see Table 1 Debyser and Gadel, 1981). The presence of sulfur in humic substances from marine sediments was previously noted by Nissenbaum and Kaplan (1972). 

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