Humic acid complexes, 538 effect

Czerwinski K., Kim J. I., Rhee D. S., and Buckau G. (1996) Complexation of trivalent actinide ions (Am, Cm ) with humic acid the effect of ionic strength. Radiochim. Acta 72(4), 179-187. 

NMR spectra of humin from three major types of depositional environments, aerobic soils, peats, and marine sediments, show significant variations that delineate structural compositions. In aerobic soils, the spectra of humin show the presence of polysaccharides and aromatic structures most likely derived from the lignin of vascular plants. However, another major component of humin is one that contains paraffinic carbons and is thought to be derived from algal or microbial sources. Hydrolysis of the humin effectively removes polysaccharides, but the paraffinic structures survive, indicating that they are not proteinaceous in nature. The spectra of humin differ dramatically from that of their respective humic acids, suggesting that humin is not a clay-humic acid complex. 

Helal AA, Imam DM, Khalifa SM, et al. 1998b. Effect of some environmental ligands and fertilizers on humic acid complexation with strontium. J Radioanal Nucl Chem 232(1-2) 159-161. 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

Onken, B.M. and Traina, S.J. The sorption of p3U ene and anthracene to humic acid-mineral complexes effect of fractional organic carbon content. J. Environ. Qual, 26(1) 126-132,1997. 

The effect of solution chemistry on the speciation of the organic contaminant 1-naphtol (1-hydroxynaphthalene) and its complexatiom with humic acid is reported by Karthikeyan and Chorover (2000). The complexation of 1-naphtol with humic acid (HA) was studied during seven days of contact, as a function of pH (4 to 11), ionic strength (0.001 and 0.1 M LiCl), and dissolved concentration (DO of 0 and 8 mg L ) using fluorescence, UV absorbance, and equilibrium dialysis techniques. In a LiCl solution, even in the absence of HA, oxidative transformation of 1-naphtol mediated by was observed. In addition, the presence of humic acid in solution, in the absence of DO, was found to promote 1-naphtol oxidation. These reactions are affected by the solution chemistry (pH, ionic strength, and cation composition). 

Fig. 16.20 Fluorescence quenching (FQ) of 1-naphthol in the presence of HA as a function of pH and reaction time (1-naphthol = 8pmol LHA = 11 ppm C ionic strength of O.IM LiQ) F and F denote fluorescence intensities in the absence and in the presence of the quencher (HA), respectively. Reprinted with permission from Karthikeyan KG, Chorover J (2000) Effects of solution chemistry on the oxidative transformation of 1-naphtol and its complexation with humic acid. Environ Sci Technol 34 2939-2946. Copyright 2000 American Chemical Society...

Sorption on magnetite as a function of groundwater composition shows that, under anoxic conditions, technetium removal from solution is essentially complete after 50 days, with the exception of solutions containing phosphate ions. As pointed out earlier, phosphate was used instead of carbonate, as both are known to form anionic complexes with Tc(IV) (9). In these studies, the presence of humic acid did not affect its sorption. Strong saline solutions (up to 34 000 mg/L Cl) do not have a marked effect on the rate of technetium removal from solution either, as evident from Figure 8. 

Influence of organic complexation. Ligands whose lead complexes dissociate only partially Within the diffusion layer during the ASV plating process (i.e., complexes partially labile to ASV) (29) have little effect on k-j- and kg. For example, the presence of 10 M humic acid (21), which is partially labile to ASV, reduces the TAF for lead by 31% and the EAF by 5-25% over the range of diffusion layer thicknesses considered here. The... 

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