Marine humic acids

Choppin, G. R. Clark, S. B. 1991. The kinetic interactions of metal ions with humic acids. Marine Chemistry, 36, 27-38. 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Magni et al. [857] studied the optimisation of the extraction of metal-humic acid complexes from marine sediments. Polyarylamide gels have been... 

Pontanen and Morris [8] compared the structure of humic acids from marine sediments and degraded diatoms by infrared and C13 and proton NMR spectroscopy. Samples of marine sediments taken from the Peru continental shelf were extracted with water, sodium hydroxide (0.05mol 1 J) and sodium pyrophosphate (0.05mol l-1) under an atmosphere of nitrogen and fractionated by ultrafiltration. Humic acids of molecular weight 300000 and above were examined. Diatoms were collected from... 

The presence of suspended solid materials increases the extent of LAS biodegradation [13,28], but the rate of the process remains invariable. The influence of the particulate material is due specifically to the increased density of the microbiota associated with sediments. However, suspended solids may also reduce the bioavailability of IAS as a result of its sorption onto preferential sites (e.g. clays, humic acids), although this is a secondary effect due to the reversibility of the sorption process. Salinity does not affect IAS degradation directly, but could also reduce LAS bioavailability by reducing the solubility of this molecule [5], Another relevant factor to be taken into account is that biodegradation processes in the marine environment could be limited by the concentration of nutrients, especially of phosphorus and nitrogen [34],... 

Humic acids (HA) are organic polyelectrolytes, which are most commonly identified with the organic material present in contemporary solid particles. HS are present in practically all soils and suspended and bottom sediments of rivers, lakes, estuaries, and shallow marine environments. 

Comparison of IR spectra of humic acids from terrestriai soiis (A-C) and marine sediments (D-G). identification of iR bands (1) aiiphatic C-H (2) C=0 (3 and 5) amides (4) aromatic C=C and (6) C-0 in poiysaccharides. Source-. From Hue, A. Y, et al. (1974). Caracterisation Des Acides Humiques de Sediments Marins Recents et Comparaison avec ieurs Homoiogues Terrestres, Buiietin de L ENSAiA De Nancy, 16, 59-75. 

Marine organisms are rich in nitrogen and therefore the humic compounds originating from them contain high amounts of nitrogen some sedimentary humic compounds contain up to 10 times as much sulfur as the soil humic acids The nitrogen content of soil humic compounds is generally low... 

Model chemical structure of a soil, (a) Humic acid and (b) part of a fulvic acid. Source-. From (a) Kleinhempel, D. (1970). Albrecht Thaer Archiv 14, 3-14 and (b) Rashid, M. A. (1985). Geochemistry of Marine Humic Compounds, Springer-Verlag, p. 75. 

Humic substances. Analogous to the reactions described above, humic substances (the polymeric pigments from soil (humus) and marine sediments) can be formed by both enzymatic and non-enzymatic browning. High concentrations of free calcium and phosphate ions and supersaturation with respect to hydroxyapatite can sustain in soil, because adsorption of humic acids to mineral surfaces inhibits crystal growth (Inskeep and Silvertooth, 1988). A similar adsorption to tooth mineral in a caries lesion can be anticipated for polycarboxylic polymers from either the Maillard reaction or enzymatic browning. 

Hayano, H., Shinozuka, N., and Hyakutake, M. (1982). Surface active properties of marine humic acids. Yukagaku 31, 357-362. 

Rashid, M. A., Buckley, D. E., and Robertson, K. R. (1972). Interactions of a marine humic acid with clay minerals and a natural sediment. Geoderma 8,11-27. 

Laboratory microcosms with Little Rock Lake sediments inoculated with 35S042- also show a gradual increase in organically bound 35S (< 1% to > 30% of reduced S over three months) and "CRS (20% to > 50%) whether incubated anaerobically or under oxic water columns. Sediments incubated under oxic water columns showed increasing incorporation of 3SS into fulvic and humic acids after a one-month delay (up to 30% of reduced S). Whether incorporation into fulvic and humic acids followed partial oxidation to polysulfides or elemental S (cf. 46-491 is not known. However, AVS accounted for < 10% of reduced 35S in our microcosms. Recent marine studies have also shown that H S (50-521 can be directly incorporated into acrylate, a breakdown product of i-mmethylsulphoniopropionate (DMSP), but the significance of this reaction in freshwater sediments has not been examined. 

Sea water contains a much lower concentration of dissolved organic matter than river water. More than half of this dissolved organic load is of a humic nature. These dissolved organic acids tend to flocculate as the salinity increases (10). Hair and Bassett (11) have observed an increase in the particulate humic acid load of an estuary as one approaches the sea. Although no studies of the distribution of humic materials throughout an estuarine system have been performed, it would appear that estuaries and their sediments in particular, act as a major sink for the dissolved and particulate humic materials. Nissenbaum and Kaplan (12) have observed that terrestrial humic materials are not deposited at great distances from shore in the marine system. A study of the flux of particulate carbon through the Chesapeake Bay comes to a similar conclusion (13). 

Fox, L. E. (1991). Determination of aquatic humic acid carbon and nitrogen by high temperature combustion. In Marine Particle Analysis and Characterization (Hurd, D. C., and Spencer, D. W., eds.). American Geophysical Union, Washington, DC. 

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