Fulvic acids natural organic matter

Humic acids (HA) and fulvic acids (FA) are the main components of humic substances (HS), which are the most chemically and biochemically active and widely spread fractions of nonliving natural organic matter in all terrestrial and aquatic environments. They comprise a chemically and physically heterogeneous group of substances with colloidal, polydis-persed, polyelectrolyte characteristics and mixed aliphatic and aromatic nature (Senesi and Loffredo 1999). 

Color in water (apart from textile dyes, etc.) is often due to degradation of natural organic matter, resulting in colloidal humic and fulvic acids. These are best removed by precipitation with metal salts, but performance may be improved with high charge cationic polymers. 

Ritchie, J. D., and Perdue, E. M. (2003). Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter. Geochim. Cosmochim. Acta 67, 85-96. 

According to their acidity, humic substances are hydrophobic and are split into two groups humic and fulvic acids. Humic acids are stable molecules originating from the ageing of organic matter. They are responsible for water coloration and represent 40-60% of natural organic matter in rivers and lakes. Fulvic acids are smaller than the humic acids and are generally less aromatic than humic acids extracted from the same pool of DOM. 

Some previous models of dissolved natural organic matter (NOM) treated the fulvic or humic acids as charge neutral species.68 Under most natural conditions, however,... 

Natural organic matter (NOM) is derived from plant or microbial residues, or it is produced in situ in water by life cycles and by a variety of decomposition pathways. Humic material (HM) is found in surface water. Its concentration is typically about 50% of the DOM. HM itself consists of the fulvic acid (FA) fraction that is soluble in water of all pH values and has an average molar mass M of 500-2000 g moh. In contrast, the humic acid (HA) fraction is only soluble under acidic conditions. HA has an average molar mass M of 2000-5000 g mol and higher (Sigg and Stumm, 1996). The composition and structure of HM or of hu-... 

Cu, have shown toxic effects on a diverse assortment of aquatic biota (6 8). The very same metal ions, on the other hand, portray a reduction or complete eradication of toxic effects when complexed with natural organic matter. Fate and transport of metal ions in the environment are also governed by associations with fulvic acid material. Therefore, determination of stability constants between FA ligand sites and potentially hazardous metal ions should be considered fundamentally important. 

Chlorine is applied as chlorine gas, powdered calcium hypochlorite (Ca(OCl)2), or liquid sodium hypochlorite (NaOCl bleach). Chlorine reacts with the organic (natural organic matter, NOM) or inorganic (bromide ion, Br ) precursors in the water to form chlorine disinfection by-products (CBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones, chloral hydrate, and chloropicrin. Humic and fulvic acids are the predominant NOMs. When bromine exists, the chlorine oxidizes it to hypobromous acid/ hypobromite ion (HOBr/OBr ) to form bromo THMs (bromodichloromethane, BDCM, and di-bromochloromethane, DBCM), HAAs, and HANs. 

Negligible photoreaction was observed for p,p -dichlorobenzophenone (DCB), a DDT oxidation product, in air-saturated, distilled water (half-fife >15 h at 313 nm). Nevertheless, this halocarbon photoreacted (313 nm) with half-lives corrected for light attenuation of about 3 h in a filtered natural-water sample and a solution of Contech fulvic acid (Table II). The greater than four- to fivefold enhancement in photoreaction rate in this case probably results from hydrogen atom abstraction from the natural organic matter by the DCB in its excited triplet state (eq 14). 

Fulvic acids, an important, intermediate size fraction of natural organic matter, are believed to play an important role in the reduction of metals and organic pollutants. Reduction of Mn(III,IV) oxides (Sunda et al., 1983 Waite et al., 1988) and Fe(III) oxides (Waite and Morel, 1984a Waite and Morel, 1984c Finden et al., 1984) by fulvic acid has been examined extensively, under chemical conditions resembling those in the environment. 

One research area that is certain to benefit from use of these facilities is the study of molecular-scale mechanisms of bioremediation and phytoremediation, where knowledge of the spatial distribution of contaminant species at the cellular level is critical for understanding reaction mechanisms and locations within or external to cells. Microfluorescence tomography is already beginning to yield this information in three dimensions at spatial scales of a few microns. Another growth area that will exploit X-ray microscopes is the characterization of natural organic matter and its interaction with mineral surfaces under in situ conditions. An X-ray microscopy study of fulvic acid in aqueous solutions at the ALS has already provided the first direct images of the macromolecular conformation of fulvic acid under in situ conditions (Myneni et al. 

The formation of halogenated acetonitriles, known constituents of drinking water (McKinney et al., 1976 Oliver, 1983), was shown to be probably due to reactions of amino acids such as aspartic acid, tyrosine, and tryptophan (Trehy and Bieber, 1981 Trehy et al., 1988). Experiments by Oliver (1983) confirmed that either natural organic matter (fulvic acid) or algal products yielded these compounds under conditions similar to those used in water treatment. In addition to the nitrile derivatives, these amino acids also yield chloral and chloroform by variants of the basic pathway (Figures 5.13 and 5.14). 

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