Humic substances molecular weight

Dissolved substances, molecular weight < 10 kD (without nitrate) Absorbance (a.u.) D — ro % vjv UWW dry weather UWWF beginning of rain UWWF wet weather NW wet weather - Similar spectra steep initial slope (carboxylic acids), then shape of humic substances - Initial slope apparently steeper than for natural water and WWTP outlet, could be due to deconvolution method (removal of NOj)... 

Z. Varanini, R. Pinton, M. G. De Biasi, S. Astolfi, and A. Maggioni, Low molecular weight humic substances stimulate H -ATPase activity of plasma membrane vesicles isolated from oat (Avena sativa L.) roots. Plant Soil I53 6 (1993). 

Chin Y, Aiken G, Danielsen K (1997) Binding of pyrene to aquatic and commercial humic substances The role of molecular weight and aromaticity. Environ Sci Technol 31 1630-1635... 

The Hayase procedure [6] discussed in section 10.1.1.2 has also been applied to marine sediments. Sedimentary fulvic acid exhibited increasing hydrophilic character with increasing molecular weight. The method used was effective for hydrophobichydrophilic characterization of humic substances. 

Humic substances are anionic polyelectrolytes of low to moderate molecular weight (500 - 20 000) their charge is due primarily to partially deprotonated carboxylic and phenolic groups (see Fig. 4.15). 

Humic substances High-molecular-weight organic compounds that are variable in composiUon, have complex structures, and are relaUvely inert. They comprise a large fracUon of the DOM. Found in sods, sediment, fresh, and seawater. 

Zhang X, Minear RA (2006) Formation, adsorption and separation of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances. Water Res 40(2) 221-230... 

Zhang X, Minear RA, Barrett SE (2005) Characterization ofhigh molecular weight disinfection byproducts from chlorination of humic substances with/without coagulation pretreatment using UF-SEC-ESI-MS/MS. Environ Sci Technol 39(4) 963-972... 

Humic substances A series of relatively high-molecular-weight, yellow- to black-colored substances formed by secondary synthesis reactions. The term is used as a generic name to describe the colored material or its fractions obtained on the basis of solubility characteristics. These materials are distinctive to the soil (or sediment) environment in that they are dissimilar to the biopolymers of microorganisms and higher plants (including lignin)... 

The enhancement of kerosene dissolution occurs even at low humic acid content in the aqueous solution. In view of the fact that humic substances are relatively high molecular weight species containing nonpolar organic moieties, Chiou et al. (1986) assumed that a partition-like interaction between a solute of very low solubility in aqueous solution and a microscopic organic environment of dissolved humic molecules can explain solute solubility enhancement. 

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