Natural organic matters

In contrast, Perdue and Wolfe (1982) observed that DOM retarded the basic hydrolysis of the octyl ester of 2,4-D. They found that the base-catalyzed rate constant was reduced in proportion to the fraction of the hydrophobic ester that was associated with the DOM. Perdue (1983) has proposed a micelle-type model to rationalize these results and those presented for atrazine. Perdue compares the physical characteristics of DOM, which is negatively charged at environmental pHs, to those of anionic surfactants. Anionic surfactants have been demonstrated to increase hydrolysis rates for acid-catalyzed processes and decrease rates for base-catalyzed processes (Fendler and Fendler, 1975). Rate enhancements for acid-catalyzed hydrolysis reactions are attributed to stabilization of the positive charge that is developed in the transition state, whereas base-catalyzed hydrolysis reactions are impeded due to destabilization of the negatively charged transition state. Although this is an attractive model, it remains largely untested. 

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Water and Waste Water Treatment. PAG products are used in water treatment for removal of suspended soHds (turbidity) and other contaminants such as natural organic matter from surface waters. Microorganisms and colloidal particles of silt and clay are stabilized by surface electrostatic charges preventing the particles from coalescing. Historically, alum (aluminum sulfate hydrate) was used to neutralize these charges by surface adsorption of Al cations formed upon hydrolysis of the alum. Since 1983 PAG has been sold as an alum replacement in the treatment of natural water for U.S. municipal and industrial use. 

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

Equilibrium complexation constants for Cu reactions with natural organic matter and the details of Cu speciation are bound to remain somewhat uncertain, since the composition of the complexing molecules varies from site to site. What is not in dispute is that the fraction of dissolved copper present as free aquo Cu is probably very small in any natural water. In extremely pristine waters, hydroxide and carbonate complexes may dominate, but organic complexes usually dominate in waters containing more than a few tenths of a mg/L organic carbon. 

Davis, ]. A. (1984). Complexation of trace metals by adsorbed natural organic matter. Geochim. Acta 48, 679-691. 

Dunnivant FM, RP Schwarzenbach, DL Macalady (1992) Reduction of substituted nitrobenzenes in aqueous solutions containing natural organic matter. Environ Sci Technol 26 2133-2141. 

McCarthy JF, Czerwinski KR, Sanford WE, et al. 1998a. Mobilization of transuranic radionuclides from disposal trenches by natural organic matter. J Contain Hydrol 30 49-77. 

McCarthy JF, Sanford WE, Stafford PL. 1998b. Lanthanide field tracers demonstrate enhanced transport of transuranic radionuclides by natural organic matter. Environ Sci Technol 32(24) 3901-3906. 

Chemical oxidation reactions incorporating contaminants into natural organic matter... 

The chemical composition of the soil and groundwater, specifically the amount of natural organic matter (NOM) and other reduced species, such as iron (II) or manganese (II) often analyzed as the chemical oxygen demand (COD) of the soil, or the soil oxidant demand. 

Natural organic matter Nonpurgeable organic carbon Parts per million by volume Permeable reactive barriers Polyvinyl chloride... 

Ritter K, Aiken GR, Ranville JF, Bauer M, Macaladi DL (2006) Evidence for the aquatic binding of arsenate by natural organic matter suspended Fe(III). Environ Sci Technol 40 5380-5387... 

Organic matter is also the essential component of natural soils and its association with microorganisms may influence the behavior and fate of toxic metals. A variety of batch complexation experiments were performed by Borrok et al. (2007) in single, binary and ternary systems for the three components natural organic matter (NOM), bacterium (B. subtilis) and metals (Pb, Cu, Cd, and Ni) to determine the significance of ternary complexation. They found that the formation of bacteria-metal-NOM complex is a rapid, fully-reversible chemical process. The stability of bacteria-metal-NOM complexes increases with the decrease of pH. All NOM fractions form ternary complexes to similar extents at circumneutral pH, but humic acid becomes the dominant NOM fraction in ternary complexes at low pH. The abundance of humic acid in ternary form is greatest with Ni or Cd systems and less with Pb and Cu systems. Their results suggest that... 

Natural organic matter (Chefetz et al. 2000) Cuticular materials (Chen et al. 2005)... 

A Natural organic matter (Salloum et al. 2002) O Humic acids (Simpson et al. 2003)... 

Accardi-Dey A, Gschwend P (2002) Assessing the combined roles of natural organic matter and black carbon as sorbents in sediments. Environ Sci Techno 1 34 21-29... 

Chefetz B, Deshmukh A, Hatcher P, Guthrie E (2000) Pyrene sorption by natural organic matter. Environ Sci Technol 34 2925-2930... 

Salloum M, Chefetz B, Hatcher P (2002) Phenanthrene sorption by aliphatic-rich natural organic matter. Environ Sci Technol 36 1953-1958... 

Sheng GY, Xu SH, Boyd SA (1996b). Mechanism(s) controlling sorption of neutral organic contaminants by surfactant-derived and natural organic matter. Environ Sci Technol 30 1553-1557... 

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). 

The octanol-water partition coefficient KqW provides a direct estimate of hydrophobicity or of partitioning tendency from water to organic media such as lipids, waxes and natural organic matter such as humin or humic acid. It is invaluable as a method of estimating KoC, the organic carbon-water partition coefficient, the usual correlation invoked being that of Karickhoff (1981)... 

Tratnyek PG, Scherer MM, Deng BL (2001) Effects of natural organic matter, anthropogenic surfactants, and model quinones on the reduction of contaminants by zero-valent iron. Water Res 35 4435 4443... 

In aquifers containing significant amounts of natural organic matter, benzene migration is retarded by sorption to the organic surfaces. 

Campbell, P. G. C., Twiss, M. R. and Wilkinson, K. J. (1997). Accumulation of natural organic matter on the surfaces of living cells implications for the interaction of toxic solutes with aquatic biota, Can. J. Fish. Aquat. Sci., 54, 2543-2554. 

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