Dissolved humic substances

Comparing the results on direct discharges with the results of the SFA for Guiyu of 186 t of DeBDE accumulating over 1 year in a land disposal, the emission of 6 kg would account for 3 x 10 3% leached material within one year, which is in the range of 3 x 10-3 to 3 x 10 2% that have been calculated by Choi et al. (2009) [41] for leaching of DeBDE in contact with dissolved humic substances from TV housing plastics. 

Kopinke F, Georgi A, Mackenzie K (2001) Sorption of pyrene to dissolved humic substances and related model polymers. 1. Structure-property correlation. Envion Sci Technol 35 2536-2542... 

Schlautman, M.A., Morgan, JJ. (1993b) Binding of a fluorescent hydrophobic organic probe by dissolved humic substances and organically-coated aluminum oxide surfaces. Environ. Sci. Technol. 27, 2523-2532. 

Georgi A, Trommler U, Reichl A, Kopinke F-D (2008) Influence of sorption to dissolved humic substances on transformation reactions of hydrophobic organic compounds in water. Part II hydrolysis reactions. Chemosphere 71 1452-1460... 

Role of Dissolved Humic Substances in Pollutant-Solid... 

CMC Critical micelle concentration COMs Complex organic mixtures DHS Dissolved humic substances... 

The amphiphilic nature of dissolved humic substances (DHS) lends them the ability to associate with both hydrophobic organics and polar or ionic species [62-64]. Inorganic ions or mineral colloids in solution will interact with the electrically active surface of humic material in solution or in the solid phase according to the same bonding forces which lead to the association between SP0M and the solid mineral matrix. Humic matter in water is associated with... 

It is commonly reported that dissolved humic substances (i. e., DHS) tend to coat mineral particles and thereby affect the surface chemistry of those materials. DHS coat the surfaces of solid particles even when they are present at very low concentrations. They furthermore impart a negative charge to the surfaces which they coat. The organic coating is expected to have a great significance on subsequent adsorption of various pollutants [88,91-93,287,288]. 

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. 

The most striking characteristic of the dissolved humic substances is their chromophoric nature. As part of the DOM, they impart a yellow-brown cast to marine and freshwaters and, hence, are part of the CDOM pool. Terrestrial hiunic substances compose a significant fraction of the riverine DOM entering the ocean. In seawater, humic substances compose 5 to 15% of the HMW DOM. Differences exist in the bulk properties of marine and terrestrial humic substances. These are summarized in Table 23.6. They have been used to trace the fate of terrestrial organic matter in the ocean. 

CASRN 1928-44-5 molecular formula C16H22CI2O3 FW 333.25 ChemicaPPhysical The second-order hydrolysis rate constants at 24 °C and pHs 8.88, 10.04, and 10.39 were 4.8, 3.1, and 4.4/M-sec, respectively. In the presence of dissolved humic substances, the overall hydrolysis rate decreased. It was concluded that the humic-bound 2,4-D, / -octyl ester was protected from hydrolysis under alkaline conditions by a factor equal to the fraction of ester associated with the humic substances (Perdue and Wolfe, 1982). 

When prometryn in aqueous solution was exposed to UV light for 3 h, the herbicide was completely converted to hydroxypropazine. Irradiation of soil suspensions containing prometryn was found to be more resistant to photodecomposition. About 75% of the applied amount was converted to hydroxypropazine after 72 h of exposure (Khan, 1982). The UV (A = 253.7 nm) photolysis of prometryn in water, methanol, ethanol, /i-butanol, and benzene yielded 2-methylthio-4,6-bis(isopropylamino)-s-triazine. At wavelengths >300 nm, photodegradation was not observed (Pape and Zabik, 1970). Khan and Gamble (1983) also studied the UV irradiation (A = 253.7 nm) of prometryn in distilled water and dissolved humic substances. In distilled water, 2-hydroxy-4,6-bis(isopropylamino)-5-triazine and 4,6-bis(isopropylamino)-5-triazine formed as major products. 

Hassett, J. P., and E. Milicic, Determination of equilibrium and rate constants for binding of a polychlorinated biphenyl congener by dissolved humic substances , Envion. Sci. Technol, 19, 638-643 (1985). 

Traina, S. J., D. C. McAvoy, and D. J. Versteeg, Association of linear alkylbenzenesulfonates with dissolved humic substances and its effect on bioavailability , Environ. Sci. Technol., 30,1300-1309 (1996). 

These techniques may further enhance the ability of 31P FT-NMR spectroscopy to be used for the identification of hydrosphere DOP. We have demonstrated already that 31P NMR spectroscopy is a viable technique for DOP identification and characterization. 31P NMR spectroscopy may eventually be useful through several of the techniques mentioned in this chapter for studying interactions of DOP with dissolved humic substances, colloids, and seston and particulate adsorption. Hence, 31P FT-NMR spectroscopy... 

Variation among Sampling Sites. Dissolved humic substance samples from seven end-member environments were isolated for study. Autochthonous inputs to DOM were expected to dominate in Big Soda Lake and in Island Lake, which is a groundwater-sustained eutrophic lake in the sandhills of western Nebraska. Allochthonous inputs to DOM from a swamp environment predominate in the Suwannee River. They also dominate in the Calcasieu River in western Louisiana, but the proportion of swampland is much lower there. The Temi River is a tropical blackwater tributary of the Orinoco River in Venezuela, where allochthonous inputs dominate. The entire Sagavanirktok River basin is located north of the tree line on the North Slope of Alaska a mixture of allochthonous and autochthonous inputs was expected for the various rivers and lakes in this basin. Lastly, Hidden Lake Creek, which is the outlet of Hidden Lake on the Kenai Peninsula of Alaska, was sampled to determine if nutrient inputs from decaying salmon were contributing to primary production and autochthonous inputs to DOM. 

H NMR data from these seven sites are presented by spectral peak-height ratios in Table III. The sites were listed in order of increasing aromatic plus olefinic carbon percentages. Fulvic acids from all the lake samples are much lower in aromatic plus oleflnic carbon content than those from river samples. These results confirm the hypothesis that autothonous inputs result in dissolved humic substances that have a low aromatic plus oleflnic carbon content. The lake samples also are lower in the ratios of peak 2 (carboxylated chains and aliphatic ketones), peak 3 (carbohydrates), and peak 4 (phenolic tannins and lignins) to peak 1 (branched methyl groups and alicyclic ali-phatics) than are the river samples. 

Table III H-NMR Spectral Peak-Height Ratios and Aromatic Plus Olefinic Carbon Contents of Dissolved Humic Substances...

Recoveries of DOC were variable among sampling sites most of this variability was apparently caused by losses during the laboratory isolation procedure. The many steps in the isolation procedure for dissolved hydrophilic substances might have resulted in loss of as much as 50% of that fraction. The procedure used to concentrate DOC in the dissolved-humic-substances fraction increased recovery, but about one-third of it still... 

Characterization of Samples. Fifty-five samples of dissolved humic substances were isolated and characterized during the first five sampling cruises. Characterizations of samples obtained during the first two sampling cruises included elemental analyses, molecular-weight distributions, acid-base titrimetry, solution-density determinations, stable-carbon-isotope determinations, and determinations of 13C NMR and lH NMR spectra. The... 

Figure 5. lH NMR spectra of dissolved humic substances (A) from the Ohio River at Olmsted, Illinois and (B) from the Mississippi River near St Fran-dsville, Louisiana sampled July-August 1987. 

Figure 6. H NMR spectra of dissolved humic substances from (A) the Illinois River at Hardin, Illinois (B) the Arkansas River at Pendleton, Arkansas and (C) the Mississippi River downstream from Belle Chasse, Louisiana sampled...

Data in this and other reports indicate three sources for dissolved organic substances in rivers, lakes, and reservoirs lignins, carbohydrates, and lipids. This study and others using degradative approaches (24) clearly established lignin as a precursor for dissolved humic substances. Similarly, carbohydrates are known to be a component of dissolved organic substances in natural waters (I). 

The aliphatic alicyclic hydrocarbon precursor is not well recognized as the major aliphatic component in dissolved humic substances, although it was previously postulated to occur (II). This precursor might arise from terpenoid hydrocarbon lipids, but the data presented in this chapter favor polyunsaturated lipid precursors that are oxidatively coupled and cyclized by free-radical mechanisms (20). Degradative studies have not identified this aliphatic component in recognizable fragments. The quantitative, structural-model approach presented here combines the results of 13C NMR, NMR,... 

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