Fulvic acids ordered materials

The Table shows a great spread in Kd-values even at the same location. This is due to the fact that the environmental conditions influence the partition of plutonium species between different valency states and complexes. For the different actinides, it is found that the Kd-values under otherwise identical conditions (e.g. for the uptake of plutonium on geologic materials or in organisms) decrease in the order Pu>Am>U>Np (15). Because neptunium is usually pentavalent, uranium hexavalent and americium trivalent, while plutonium in natural systems is mainly tetravalent, it is clear from the actinide homologue properties that the oxidation state of plutonium will affect the observed Kd-value. The oxidation state of plutonium depends on the redox potential (Eh-value) of the ground water and its content of oxidants or reductants. It is also found that natural ligands like C032- and fulvic acids, which complex plutonium (see next section), also influence the Kd-value. 

There are relatively few studies that have measured the P content of dissolved organic material however, available information appears to indicate that the P content of DOM can act as a broad indicator of the conditions under which the DOM was formed. The P content of dissolved fulvic acids and colloids in aquatic ecosystems has been determined by elemental analysis (McKnight et al., 1985 1997). The P content of fulvic acids varies by more than an order of magnitude across different ecosystems (Table II). Fulvic acids from Thoreau s Bog in Massachusetts have a high P content compared... 

The MRTs of individual humus fractions also vary, as can be seen from Table 8. The MRT of the original soil (Melfort silt loam) was 870 years whereas the MRTs of individual fractions ranged from 25 to 1410 years. For both humic and fulvic acids, the acid hydrolyzable fractions (6A HCl for 18 hours) had lower MRTs than the nonhydrolyzable fractions. This result is in accord with expectations, because the hydrolyzable material would include the carbon of readily decomposable substrates (e.g., carbohydrates and amino acids). Stability of the major humus fractions followed the order humin = humic acid > fulvic acid (Campbell et al., 1967a). 

Bourbonniere and Meyers (unpublished) hydrolyzed humic substances from Lake Huron sediments with 5N NaOH at 170°C for 12 hours under a nitrogen atmosphere and found the following organic acids -Ci6 and n-Cig monocarboxylic acids lactic acid, 2-hydroxybutanoic acid, 3,4-dihydroxy-butanoic acid, oxalic acid, and succinic acid. It was proposed that the smaller organic acids were derived from cellulose-related materials. 2-Hy-droxybenzoic acid, 4-hydroxybenzoic acid, 2,5-dihydroxy-3-pentenoic acid, and vanillic acid were also observed. It was believed that 4-hydroxybenzoic acid and vanillic acid originated from lignin and that the ratio of 3,4-dihy-droxybutanoic acid to vanillic acid indicates the proportion of cellulose to lignin. The proportion was in the order of fulvic acid > humic acid > humin. 

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