Humic acids naturally occurring

Humic acid Naturally occurring high-molecular-mass organic compounds which are acid-soluble but are precipitated by base. 

The behavior of plutonium in surface waters is dependent upon the oxidation state and the nature of the suspended solids and sediments. Plutonium(lll) and plutonium(IV) are considered to be the reduced forms of plutoniwm while plutonium(V) and plutonium(VI) are the oxidized forms. The oxidized forms of plutonium are found in natural waters when the concentrations of dissolved organic matter or dissolved solids are low (Nelson et al. 1987). Humic materials (naturally occurring organic acids) were found to reduce plutonium(V) to plutonium(IV) in sea water. This was followed by adsorption of plutonium(IV) onto iron dioxides and deposition into the sediments (Choppin and Morse 1987). 

NOTE There are various types of organic contaminants that can be present in boiler FW, including trace amounts of pesticides and naturally occurring humic, fulvic, and tannic acids, and solvent-extractable oily matter, such as nonvolatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and the like. 

Shimp J, FK Pfaender (1985b) Influence of naturally occurring humic acids on biodegradation of monosubstituted phenols by aquatic bacteria. Appl Environ Microbiol 49 402-407. 

Recently, Burkhard (2000) reviewed contaminant sorption by dissolved organic matter. Using several hundreds of UCC-water partition coefficients (A doc) reported in these studies, he found that UCC-water partition coefficients for naturally occurring DOC (humic and fulvic acids, sediment pore water, soil pore water, groundwater, and surface water) was best described by... 

An array of physical, chemical and biological methodologies exist which may deal at various levels of efficiency with both naturally occurring organic matter (NOM) such as humic acids and those resulting from... 

Naturally occurring substances compounds leached from the earths crust (calcium, heavy metals) and leachates from soils and sediments (humic and fulvic acids). 

All three chloroacetic acids (chloroacetic acid [MCA], dichloroacetic acid [DCA], and trichloroacetic acid [TCA]) are naturally occurring (7), with TCA being identified in the environment most frequently (reviews (278, 405 108)). However, these chlorinated acetic acids also have anthropogenic sources. The major source of natural TCA appears to be the enzymatic (chloroperoxidase) or abiotic degradation of humic and fulvic acids, which ultimately leads to chloroform and TCA. Early studies (409) and subsequent work confirm both a biogenic and an abiotic pathway. Model experiments with soil humic and fulvic acids, chloroperoxidase, chloride, and hydrogen peroxide show the formation of TCA, chloroform, and other chlorinated compounds (317, 410-412). Other studies reveal an abiotic source of TCA (412, 413). 

Fulvic acids A group of naturally occurring organic compounds of biological origin that are common in the A horizons of soils and other natural environments. While humic acids are only soluble in water at pH > 2, fulvic acids are water-soluble under all pH conditions (Drever, 1997), 113-114 (compare humic acid and humin). 

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