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Humic substances acetate

Extractable concentrations of sediment-bound zinc were positively correlated with zinc concentrations in deposit feeding clams (Luoma and Bryan 1979). Availability of sediment zinc to bivalve molluscs was higher at increased sediment concentrations of amorphous inorganic oxides or humic substances, and lower at increased concentrations of organic carbon and ammonium acetate-soluble manganese. Zinc uptake by euryhaline organisms was enhanced at low water salinity (Luoma and Bryan 1979). [Pg.640]

Muscolo, A., Panuccio, M. R., Sidari, M., and Nardi, S. (2005).The effects of humic substances on Pinus callus are reversed by 2,4-dichlorophenoxy acetic acid. J. Chem. Ecol. 31(3), 577-590. [Pg.335]

From studies carried out at the Directorate of Fisheries Research at Lowestoft (DFR) four types of complex have been chosen to illustrate the range of complex radiocobalt species that might be encountered in environmental waters. They are either species of known importance in the environment, such as cyanocobalamin and complexes with humic substances, or those generated specifically in the nuclear industry (e.g. complexes with ethylene diamine tetra-acetic acid (EDTA) or picolinic acid) and which are able to persist for significant periods following discharge to the aqueous environment. [Pg.373]

About half of the total Mn in sediments was removed by the low pH extractants. Ammonium acetate removed a smaller, but significant, quantity of Mn. Less than 1 percent of the Mn was solubilized with the humic substances dissolved by ammonia. [Pg.588]

Figure 6. Zinc concentrations in Scrobicularia plana from southwest England as related to (a, above) ammonium acetate-soluble Zinc in sediments from southwest England (r = 0.62) (h, top right) the product of ammonium acetate-soluble zinc and the ratio of humic substance concentrations (H) (absorbance in a IN ammonia extract) to total organic carbon (C) (r = 0.82) and (c, bottom right) the product of (ZnAmAc) X (H/C) X (Muoxai) whcrc Muoxai = oxalate soluble manganese where present at concentrations > 350 ixg/g (r = 0.84). Figure 6. Zinc concentrations in Scrobicularia plana from southwest England as related to (a, above) ammonium acetate-soluble Zinc in sediments from southwest England (r = 0.62) (h, top right) the product of ammonium acetate-soluble zinc and the ratio of humic substance concentrations (H) (absorbance in a IN ammonia extract) to total organic carbon (C) (r = 0.82) and (c, bottom right) the product of (ZnAmAc) X (H/C) X (Muoxai) whcrc Muoxai = oxalate soluble manganese where present at concentrations > 350 ixg/g (r = 0.84).
The correlations indicated that the availability of Zn to the bivalves increased -when concentrations of either amorphous inorganic oxides or humic substances increased in sediments. Availability -was reduced at increased concentrations of organic carbon and, in San Francisco Bay, ammonium acetate-soluble Mn. Concentrations of biologically available Zn in solution and lo-w salinities may also have enhanced Zn uptake, although the roles of these variables -were less obvious from the statistical analysis. [Pg.607]

Research on the chemical properties of humic substances was extended by the Swedish investigator Berzelius (1839). One of his main contributions was the isolation of two light-yellow-colored humic substances from mineral waters and a slimy mud rich in iron oxides. They were obtained from the mud by extraction with base (KOH), which was then treated with acetic acid containing copper acetate. A brown precipitate was obtained ctilled copper apocrenate. When the extract was neutralized, another precipitate was obtained, called copper crenate. The free acids, apocrenic and crenic acids, were then brought into solution by decomposition of the copper complexes with alkali. These newly described humic substances were examined in considerable detail, including isolation, elementary composition, and properties of their metal complexes (Al, Fe, Cu, Pb, Mn, etc). [Pg.15]

Large volumes of water often need to be processed to obtain sufficient quantities of aquatic humic substances filtration is the slowest step in this process. In a comparison of filter flow rates, Cranston and Buckley (1972) found filtering times for 47 mm (millimeter) diameter filters increased in this order glass-fiber filters < silver-membrane filters < organic-membrane filters (cellulose-acetate and cellulose-nitrate). They also report that substantial variation exists between different silver filters from the same manufacturer. This is caused by variation in permeability (number of pores per unit area), not pore size, and did not occur with the other filters studied. [Pg.368]

The insolubility of humic substances in nonpolar organic solvents has limited the use of solvent extraction as a method of isolating humic substances from water. The most effective method for solvent extraction was reported by Eberle and Schweer (1974). Humic acid was efficiently extracted with trioc-tylamine/chloroform at pH 5 and was recovered by back-extracting with water at pH 10 or above. Butanol has been used to extract freeze-concentrated humic substances however, not all the material was extracted (Shapiro, 1957). Another method involves acidification of a sample with acetic acid, followed by extraction with isoamyl alcohol. Humic acid precipitates at the interface (Martin and Pierce, 1975). This method is slow 5 hours were required to extract 100 mL of sample. No data on the behavior of fulvic acid in this solvent extraction were presented. [Pg.374]

Acidification of aqueous concentrates and extracts to pH near 1 is the standard procedure to precipitate humic from fulvic acid, and this procedure also has been applied to aquatic humic substances (Thurman and Malcolm, 1981). Aquatic humic substances that interact significantly with metal ions can be precipitated from water by addition of lead(Il) nitrate (Klocking and Mucke, 1969). Co-precipitation of aquatic humic materials with aluminum, copper, iron, and magnesium hydroxides has been used to recover aquatic humic substances from various types of water (Jeffrey and Hood, 1958 Williams and Zirino, 1964 Zeichmann, 1976). Humic acids can also be precipitated from an unconcentrated water sample by adding acetic acid and isoamyl alcohol to a sample contained in a separatory funnel, and after shaking, humic acid precipitates at the alcohol-water interface (Martin and Pierce, 1971). Precipitation methods are among the crudest of fractionation methods... [Pg.415]

Acylation of aquatic humic substances with acetic anhydride in a variety of solvents was found to be unsatisfactory because of dehydration and 7r-bond formation. The mild acylating reagent, A-acetylimidazole, did not give complete acylations of hindered hydroxyl groups. Acetyl chloride was tested under a variety of conditions and gave complete derivatization of primary and secondary hydroxyls under the conditions shown in reaction (3) ... [Pg.423]

Several problems are inherent in this method, so the results should be considered as quite operational (Dubach et al., 1964 van Dijk, 1966 Stevenson and Goh, 1972 Holtzclaw and Sposito, 1979 Perdue, 1979 Perdue et al., 1980). First, unlike the barium hydroxide reagent used for total acidity, 0. IM calcium acetate is poorly buffered. The equilibrium pH, which determines the extent to which the acidic functional groups of humic substances will react, is dependent on the amount of humic substances added to the 50 mL of calcium acetate. Perdue et al. (1980) demonstrate that the binding of Ca to the humic substance sample displaces additional protons that do not react if sodium acetate or pyridine is used as the exchange base. It cannot be assumed that those excess protons are derived exclusively from carbbXyr groups. [Pg.512]

Second, an even more serious problem with this method is the critical nature of the filtration step (Holtzclaw and Sposito, 1979 Perdue, 1979 Perdue et al., 1980). Any moderately acidic functional groups (pKa 7-10) that are soluble in the equilibrium mixture (pH 6-7) will be titrated along with acetic acid when the filtrate is titrated to pH 9.8 (see Fig. 7). All the functional groups detected in that titration are simply assumed to be carboxyl groups. Thus, while the use of high concentrations of humic substances can lead to underestimation of carboxyl content, the complexation... [Pg.512]

Table II illustrates the types of structures which may be distinguished from each other by dipolar dephasing experiments on humic substances. Clearly, methine and methyl, protonated aromatic and non-protonated aromatic, ketone and aldehyde, ketal and acetal carbons and also protonated olefinic and non-protonated olefinic carbon can be distinguished. Examples of the use of the method (, 13), are shown in Figure 5. Table II illustrates the types of structures which may be distinguished from each other by dipolar dephasing experiments on humic substances. Clearly, methine and methyl, protonated aromatic and non-protonated aromatic, ketone and aldehyde, ketal and acetal carbons and also protonated olefinic and non-protonated olefinic carbon can be distinguished. Examples of the use of the method (, 13), are shown in Figure 5.
Change the elution solvent so that the interferences remain on the solid phase and the analyte is eluted. An example is the sorption of a herbicide from water and its elution from a reversed-phase sorbent, C-18, using ethyl acetate rather than methanol. Ethyl acetate does not remove the majority of the natural organic substances (humic substances)" from the sorbent, while methanol does. Thus, the chromatogram is considerably cleaner with the ethyl-acetate eluent. [Pg.66]


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See also in sourсe #XX -- [ Pg.325 , Pg.326 ]




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