Marine humic substances

FIGURE 2. Elemental composition of reference humic substances. Marine input sediment from Kerguelen Islands terrestrial input sediment from Mahakam Delta (Indonesia). 

Sabljic, A., Lara, R., Ernst, W. (1989) Modelling association of highly chlorinated biphenyls with marine humic substances. Chemosphere 19, 1665-1676. 

Pierce RH Jr, Felbeck GT Jr (1972) A comparison of three methods of extracting organic matter from soils and marine sediments. In Povoledo D, Golterman HL (eds) Humic Substances. Center for Agriculture Publication and Documentation, Wageningen, Netherlands, pp 217-232... 

Mayer, L.M., Schick, L.L., Loder, T.C. 1999. Dissolved protein fluorescence in two main estuaries. Marine Chemistry, 64, 171-179. Miano, T.M., Senesi N., 1992. Synchronous excitation fluorescence spectroscopy applied to soil humic substances chemistry. Sci Total Environ, 117/118, 41-51. 

Florence, T. M., Powell, H. K. J., Stauber, J. L. and Town, R. M. (1992). Toxicity of lipid-soluble copper(II) complexes to the marine diatom Nitzschia Closterium -amelioration by humic substances, Water Res., 26, 1187-1193. 

The Hayase procedure [6] discussed in section 10.1.1.2 has also been applied to marine sediments. Sedimentary fulvic acid exhibited increasing hydrophilic character with increasing molecular weight. The method used was effective for hydrophobichydrophilic characterization of humic substances. 

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial role in many biogeochemical processes. 

The most striking characteristic of the dissolved humic substances is their chromophoric nature. As part of the DOM, they impart a yellow-brown cast to marine and freshwaters and, hence, are part of the CDOM pool. Terrestrial hiunic substances compose a significant fraction of the riverine DOM entering the ocean. In seawater, humic substances compose 5 to 15% of the HMW DOM. Differences exist in the bulk properties of marine and terrestrial humic substances. These are summarized in Table 23.6. They have been used to trace the fate of terrestrial organic matter in the ocean. 

Since most of the riverine DOM is comprised of humic substances, considerable attention has been fiacused on its fete in seawater. Little terrestrial DOM is detectable in seawater, suggesting the existence of an efficient removal process. This is surprising given the traditional view that humic substances are relatively refractory. Marine chemists are currently investigating the redox and photochemistry of humic substances to better understand its chemical fete in the oceans. 

Labile and refractory DOM undergo abiotic photochemical reactions in the photic zone, especially in the sea surfece microlayer where physical processes concentrate DOM into thin films. Some of these reactions appear to be important in the formation of refractory DOM and others in its degradation. For example, DOM exuded by diatoms during plankton blooms has been observed to be transformed into humic substances within days of release into surfece seawater. Laboratory experiments conducted in seawater have demonstrated that photolysis of labile LMW DOM promotes the chemical reactions involved in humification and produces chemical structures foimd in marine humic substances. 

Calculated equilibrium speciation of (a) mercury and (b) copper during estuarine mixing of hypothetical river water with seawater. Hum, humic substance. Note logarithmic scale on y-axis. Source. From Mantoura, R. F. C., et al. (1978). Estuarine and Coastal Marine Science 6, 387 08. 

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. 

Hassett IJ, Banwart WL (1989) The sorption of nonpolar organics by soils and sediments In Sawhney BL, Brown K. (eds) Reactions and movement of organic chemicals in soils Soil Science Society of America, Madison, Wl, pp 31 5p Hayes MHB, Malcom RL (2001) Considerations of compositions and aspects of the structure of humic substances. In Clapp CE, Hayes MHB, Senesi N, Bloom PR Jardine PM, Humic substances and chemical contaminants. Soil Science Society of America, Madison, Wl, pp 1-39 Herbillon AJ, Erankart R, Vielvoye L (1981) An occurrence of interstratified kaoUnite-smectite minerals in a red-black soil top sequence. Clay Miner 16 195-201 Horne RA (1969) Marine chemistry. Wiley, New York... 

Laane, R.W.P.M. and Kramer, C.3.M., 1984. Complexation of Cu + with humic substances in relation to different extraction procedures of sandy and silty marine sediments. In C.3.M. Kramer and 3.C. Duinker (eds), Complexation of Trace Metals in Natural Waters. Nijhoff/3unk Publ., the Hague, pp. 345-348. 

Raspor, B., Nurnberg, H.W., Valenta, P. and Branica, M., 1984. Studies in seawater and lakewater on interactions of trace metals with humic substances isolated from marine and estuarine sediments. 11. Voltammetric investigations on trace metal complex formation in the dissolved phase. Mar. Chem., 15 231-249. 

Tipping (1981) showed that the adsorption of terrestrial humic substances could reverse the positive electrophoretic mobility of iron oxides. Thus, both terrestrial and marine organics are strong adsorbates, able to reverse zeta potential. 

A. Nissenbaum and I.R. Kaplan, Chemical and isotopic evidence for the in situ origin of marine humic substances, Limnol. Oceanogr. 17 (1972) 570-582. 

Moran, M. A., and R. E. Hodson. 1994. Support of bacterioplankton production by dissolved humic substances from three marine environments. Marine Ecology Progress Series 110 241-247. 

Prakash, A., M. A. Rashid, and A. Jensen. 1973. Influence of humic substances of the growth of marine phytoplankton Diatoms. Limnology and Oceanography 18 516—524. 

Bushaw-Newton, K. L., and M. A. Moran. 1999. Photochemical formation of biologically available nitrogen from dissolved humic substances in coastal marine systems. Aquatic Microbial Ecology 18 285-292. 

Jones, R. I. 1998. Phytoplankton, primary production and nutrient cycling. In Aquatic Humic Substances (D. O Hessen and L. J. Tranvik, Eds.), pp. 145-176. Springer-Verlag, Berlin. Kirchman, D. L. 2000. Uptake and regeneration of inorganic nutrients by marine heterotrophic bacterial. In Microbial Ecology of the Oceans (D. L. Kirchman, Ed.), pp. 261-288. Wiley, New York. 

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