Humic substances in natural waters and their complexation with trace metals and radionuclides: a review. [129 references]

Technical Report · Mon Jul 01 00:00:00 EDT 1985

DOI:https://doi.org/10.2172/5569909· OSTI ID:5569909

Boggs, S Jr; Livermore, D; Seitz, M G

Dissolved humic substances (humic and fulvic acids) occur in surface waters and groundwaters in concentrations ranging from less than 1 mg(C)/L to more than 100 mg(C)/L. Humic substances are strong complexing agents for many trace metals in the environment and are also capable of forming stable soluble complexes or chelates with radionuclides. Concentrations of humic materials as low as 1 mg(C)/L can produce a detectable increase in the mobility of some actinide elements by forming soluble complexes that inhibit sorption of the radionuclides onto rock materials. The stability of trace metal- or radionuclide-organic complexes is commonly measured by an empirically determined conditional stability constant (K'), which is based on the ratio of complexed metal (radionuclide) in solution to the product concentration of uncomplexed metal and humic complexant. Larger values of stability constants indicate greater complex stability. The stability of radionuclide-organic complexes is affected both by concentration variables and envionmental factors. In general, complexing is favored by increased of radionuclide, increased pH, and decreased ionic strength. Actinide elements are generally most soluble in their higher oxidation states. Radionuclides can also form stable, insoluble complexes with humic materials that tend to reduce radionuclide mobility. These insoluble complexes may be radionuclide-humate colloids that subsequently precipitate from solution, or complexes of radionuclides and humic substances that sorb to clay minerals or other soil particulates strongly enough to immobilize the radionuclides. Colloid formation appears to be favored by increased radionuclide concentration and lowered pH; however, the conditions that favor formation of insoluble complexes that sorb to particulates are still poorly understood. 129 refs., 25 figs., 19 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5569909
• Report Number(s): ANL-84-78; ON: DE85015539
• Country of Publication: United States
• Language: English

Related Subjects

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54 ENVIRONMENTAL SCIENCES
ACTINIDE COMPLEXES
ACTINIDES
CHELATES
CHELATING AGENTS
CHEMICAL REACTIONS
COLLOIDS
COMPLEXES
DISPERSIONS
DOCUMENT TYPES
ELEMENTS
FULVIC ACIDS
GROUND WATER
HUMIC ACIDS
HYDROGEN COMPOUNDS
LIGANDS
METALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PH VALUE
REVIEWS
STABILITY
SURFACE WATERS
TRACE AMOUNTS
WATER