Humic substances complex nature

Laglera, L.M., G. Battaglia, and M.G. van den Berg. 2007. Constant determination of humic substances in natural waters by cathodic stripping voltammetry of their complexes with iron. Anal. Chim. Acta 599 58-66. 

Evidence of the formation of metal complexes with humic substances in natural waters has been reported by many authors (3-12). The same applied to the stability constants of the above complexes... 

In natural waters, dissolved zinc speciates into the toxic aquo ion [Zn(H20)6]2+, other dissolved chemical species, and various inorganic and organic complexes zinc complexes are readily transported. Aquo ions and other toxic species are most harmful to aquatic life under conditions of low pH, low alkalinity, low dissolved oxygen, and elevated temperatures. Most of the zinc introduced into aquatic environments is eventually partitioned into the sediments. Zinc bioavailability from sediments is enhanced under conditions of high dissolved oxygen, low salinity, low pH, and high levels of inorganic oxides and humic substances. 

Clay minerals, oxides, and humic substances are the major natural subsurface adsorbents of contaminants. Under natural conditions, when humic substances are present, humate-mineral complexes are formed with surface properties different from those of their constituents. Natural clays may serve also as a basic material for engineering novel organo-clay products with an increased adsorption capacity, which can be used for various reclamation purposes. 

Due to the various health risks of different element species, there are a multitude of applications for natural water samples in this field (e.g., Cr and Sb speciation or Br and I determination).19 The investigation of heavy metal complexes with humic substances by isotope dilution SEC-ICP-MS has been described, for example, by McSheehy and Mester.20 Copper, zinc and molybdenum were found to form complexes with similar size fractions of humic substances in seepage water samples from soils. Sturgeon s group proposed the use of solid phase microextraction (SPME)... 

Only about 20% of the DOM in natural waters consists of identifiable compounds that include carbohydrates, carboxylic acids, amino acids, and hydrocarbons (I). The remaining 80% of DOM (generally defined as humic substances) consists of complex, environmentally altered residue of plant, bacterial, and fungal origin, of moderate molecular weight (500-5000 dal-tons). This predominantly acidic undefined DOM has been classified by... 

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. 

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