Humic Substances in Natural Waters and Their Complexation with Trace Metals and Radionuclides: A Review

Boggs, Sam Jr.
Livermore, David
Seitz, Martin G.
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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 rng(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.
humic substances , natural waters , trace metals , radionuclides