Solubility humic material

Although such reactions and the consequences with respect to contaminant fate have primarily focused on soluble humic materials (Carter Suffet, 1982 Madhun et al., 1986 Traina et al., 1989 Morra et al., 1990 Puchalski et al., 1992 Engebretson von Wandruszka, 1994), the participation of microbial products in similar reactions is possible. Dohse and Lion (1994) showed that extracellular bacterial polymers enhanced the transport of phenanthrene in sand columns. The mobilization of contaminants might be beneficial to bioremediation if degradation reactions are not inhibited and substrate bioavailability is increased. Conversely, increased contaminant transport may increase the potential for contaminant movement and likewise the extent of environmental contamination. 

Shaw, L.J., Beaton, Y., Glover, L.A., Killham, K., Osborn, D. and Meharg, A.A. (2000) Bioavailability of 2,4-dichlorophenol associated with soil water-soluble humic material. Environmental Science and Technology, 34, 4721-4726. 

Larson, R. A. and Rockwell, A. L. (1980). Fluorescence spectra of water-soluble humic materials and some potential precursors. Arch. Hydrobiol. 39, 416-425. 

Two different humic materials were used in this study for comparison, a well-defined soluble humic material (Ha) that purchased from Aldrich, and a soil extracted material (SEM) that prepared by soil washing with surfactant. The soil samples of the latter were undistributed, subhumid soil collected from Tai Mei Tuk, Hong Kong. The soil samples were air-dried and screened through U.S. standard No. 10 mesh (2mm) sieve to remove coarse fragments. The fractions of organic carbon in the soil samples were determined to... 

In natural waters, Tl is not precipitated as a carbonate nor as an hydroxide, and is also hardly bound to soluble humic material. Therefore, toxicity is largely independent of water characteristics, such as hardness, dissolved organic carbon, or suspended matter (Nehr-ing, 1962 Zitko et al., 1975). 

Fulvic Acid An acid-alkali-soluble humic material, originating from the breakdown of lignin and tannins... 

Bone protein was extracted following the method described by Sealy (1986). Bone chips were demineralized in a weak HCl solution, then soaked in 0.1 M NaOH to remove base-soluble humic substances. Remaining material, which is mainly collagen, but includes non-collagenous proteins, was... 

Three methods were used in this research to measure the extent of binding of organic pollutants to dissolved humic materials. They were equilibrium dialysis, solubility measurements and changes in sorption behavior in the presence of humic materials. Other authors have used solubility measurements, ultrafiltration and volatilization measurements. The methods will be described in the following paragraphs. 

In a solubility experiment the solubility of the compound of interest is measured in the presence and absence of dissolved humic materials. Two techniques were used to measure solubility a shake and filter method similar to that used by Yalkowsky, and a flow through column technique similar to that used by May et al. 9 The measured solubilities of a number of compounds in our experiments were always higher in the presence of humic materials. This increase in the solubility is due to the binding of the compound by humic materials. In the presence of humic materials the measured solubility consists of two fractions free and bound. The free concentration should be the same in the presence or absence of humic materials. The difference between the solubilities of the compound in the presence and absence of humic materials is therefore a measurement of the bound fraction. 

Many researchers have attempted to unravel the mystery of the structure of humus. One approach has been to isolate fractions by extracting humus using various extraction procedures. These procedures result in the isolation of three or more fractions humic acid, fulvic acid, and humin. Humic material is isolated from soil by treating it with alkali. The insoluble material remaining after this treatment is called humin. The alkali solution is acidified to a pH of 1.0 and the precipitate is called humic acid, while the soluble... 

Humic materials are partially soluble in water and thus occur in both surface and groundwaters. 

A fractionation procedure has been established and widely applied to studies of humic materials [42-44]. The procedure begins with natural OM (i.e., humus) and uses an aqueous basic solution (e.g., 0.1-0.5 mol/1 NaOH and Na2C03) to solubilize a fraction of the OM. The basic extract is then acidified which causes a precipitate to form, i.e., humic acids (HA). The fraction, which remains in solution, is called fulvic acids (FA). Humin is the name given to the insoluble organic fraction that remains after extraction of humic and fulvic acids. At nearneutral pH (pH 5 - 8), which is characteristic of most natural water, the FA are the most water soluble of these three fractions. HA are somewhat less soluble, with their solubility increasing as the pH increases. Humin is insoluble at all pH values. 

It has also been shown [254] that a commercial petroleum sulfonate surfactant which consists of a diverse admixture of monomers does not exhibit behavior typically associated with micelle formation (i.e., a sharp inflection of solvent properties as the concentration of surfactant reaches CMC). These surfactants exhibit gradual change in solvent behavior with added surfactant. This gradual solubility enhancement indicates that micelle formation is a gradual process instead of a single event (i. e., CMC does not exist as a unique point, rather it is a continuous function of molecular properties). This type of surfactant can represent humic material in water, and may indicate that DHS form molecular aggregates in solution, which comprise an important third phase in the aqueous environment. This phase can affect an increase in the apparent solubility of very hydrophobic chemicals. 

Wershaw RL (1986) A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or in sediment-water systems. J Contam Hydrol 1 29-45 Whitehouse BG (1984) The effect of temperature and salinity on the aqueous solubility of polynuclear aromatic hydrocarbons. Mar Chem 14 319-332 Wolters A, Linnemann V, Herbst M, Klein M, Schaffer A, Vereecken H (2003) Pesticide volatihzation from soil Lysimeter measurements versus predictions of European registration models. J Environ Qual 32 1183-1193... 

The solubility of fuel oil no. 2, particularly the alkane and isoprenoid fractions, in seawater is increased by the presence of fulvic acid, although the solubilities of phenanthrene or anthracene, both polycyclic aromatic hydrocarbons, are unaffected by the presence of humic materials (Boehm and Quinn 1973). Unfiltered Narragansett Bay water was able to dissolve 1,560 g/L of fuel oil no. 2, although removal of... 

The principal abiotic processes that may transform thorium compounds in water are complexation by anions/organic ligands and hydroxylation. The increase in the mobility of thorium through the formation of soluble complexes with CQs, humic materials, and other anions or ligands and the decrease in the mobility due to formation of Th(OH)4 or anionic thorium-hydroxide complexes were discussed in Section 5.3.1.2. In a model experiment with seawater at pH 8.2 and freshwater at pH 6 and pH 9, it was estimated that almost 100% of the thorium resides as hydroxo complexes (Boniforti 1987). 

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