Water humic substances

Wilson, M. A., Barron, P. F., and Gillam, A. H. (1981a). The structure of fresh-water humic substances as revealed by l3C NMR spectroscopy. Geochim. Cosmochim. Acta 45, 1743-1750. 

Acid—Base Equilibria of River Water Humic Substances ... 

Because of the considerable potential of titration calorimetry as an analytical technique for characterization of the acidic functional groups of humic substances, our studies have been extended to river water humic substances. In this paper, results are presented for the thermochemical characterization of the acidic functional groups of river water humic substances from two quite different river systems 1) the Satilla River in southeastern Georgia, and 2) the Williamson River in southern Oregon. 

Titration Calorimetry of River Water Humic Substances. The concentration of river water humic substances used in all experi-... 

Concentrations of Acidic Functional Groups in River Water Humic Substances. The results of the total acidity, carboxyl... 

Table I. Concentrations of acidic functional groups in river water humic substances and soil humic acid.

The average AHj values for ionization of carboxyl groups and titratable phenolic groups and the average pKg of the titratable phenolic groups of river water humic substances are given in Table II. The previously reported AHg and pKg values for soil humic acid (28) are included for comparison. As previously mentioned, the equilibrium constants for neutralization of car-... 

Concentrate of river water humic substances dissolved in artificial seawater -28 X Skidaway River... 

Perdue, E. M. (1979). Solution thermochemistry of humic substances. II. Acid-base equilibria of river water humic substances. In Chemical Modeling in Aqueous Systems, Vol. 93 (E. A. Jenne, ed.). American Chemical Society, Washington, D.C., pp. 94-114. 

Figure 4. Distribution of Mn zones in the estuarine water humic substances system.

A specific application of environmental SPE is sample preparation of extra-large volumes (from 10 to 100 L). This work was pioneered in the early 1970s by Junk and co-workers (1974) for the analysis of trace organic compounds in water using styrene-divinylbenzene copolymers (XAD-2 resin from Rohm and Haas) and by Thurman and Malcolm (1981) and Leenheer and Stuber (1981) for the analysis of natural organic substances in water (humic substances). One can obtain the XAD resins from Supelco (Appendix Products Guide) and still follow the protocol of this early work for the isolation of contaminants and humic substances from large volumes of water (10-1000 L of water). 

Fig. 1. Hypothetical structures of humic compounds from (A) lake water (Christman, 1970), (B) soil fulvic acids (Schnitzer and Khan, 1972), (C) melanin residue of marine humus (Duursma, 1965) and (D) sea-water humic substances (Gagosian and Stuermer, 1977).

Sun L., Perdue E.M., McCarthy J.F. (1994), Using reverse osmosis to obtain organic matter from surface waters. Humic Substances in the Global Environment and Implicadons on Human Health, (Ed. N. Senesi, T.M. Miano), Elsevier Science, 901-910. 

They constitute 75% w/w of the organic matter in most soils and 50% of the organic carbon in surface waters. Humic substances are composed of complex heterogeneous mixtures of organic compounds and are characterized as being yellow to brown in color, of high relative molecular mass, and refractory. Unlike many other natural organic products, they cannot be described in terms of unique chemical structures and are operationally defined by the technique used for their extraction and fractionation. 

Any isolate of soil and water humic substances is intrinsically polydisperse, and physical and chemical properties derived from these substances are average values (Figure 2). In some cases, it is preferable to... 

Phenolic hydroxyl content is more difficult to determine by potentiometric titration owing to the weak acidic nature of phenolic hydroxyl. Phenolic hydroxyl content can, therefore, be only estimated. Again NMR can be used for estimation of phenolic hydroxyl content. Comparable values are obtained using both these methods, e.g., 1-2 meq g for water humic substances. This is less than phenolic hydroxyl content of soil humic substances, which is 3.0-3.9 meqg. Phenolic contents of water humic... 

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