General Cleanup Technology

Soil remediation with amino acids – heavy metal fixation

The project partners investigated the mobility of heavy metals in contaminated soils following the addition of an amino acid solution. The solution is obtained by hydrolyzing various organic matter, such as offal, animal by products, leather or feathers. The mixture is genotoxically safe and considered environmentally benign since it is organic in nature.

Summary

Heavy metals such as lead (Pb), cadmium (Cd) or mercury (Hg) can enter the soil from liquid manure, mining, the metallurgical industry or military activities. Unlike copper (Cu) and zinc (Zn), these metals are not required for metabolism by living organisms and hence accumulate in the environment, where they can have harmful impacts. The contaminants’ concentration, mobility and availability to plants are significant in this respect.
Recent experiments indicate that addition of an amino acid mixture to soils contaminated by heavy metals can reduce their availability.
The project partners investigated to what extent the mobility of heavy metals in soil can be altered by the addition of such an amino acid mixture. An analysis of the soluble and weakly sorbed fraction is necessary for assessing the environmental efficacy of the method.

Results:

  • The neutralized as well as unneutralized amino acid solution influences the mobility of the investigated heavy metals in an aqueous solution. This impacts the leachate output. The amino acids act as a “solution provider”.
  • Pb, Cu and Zn become more available due to amino acid action, while Cd appears to be immobilized in the short term.
  • The unneutralized amino acid solution (pH 12.56) causes a significant increase in As (arsenic) and Hg only in an aqueous 1:2 extract.
  • Amino acids bring about an increase in dissolved organic content and mobile heavy metals in the extract.
  • Amino acids do not exhibit a clearly defined impact on the heavy metal uptake by plants. Pb uptake partially decreased after addition of amino acids.
  • The LD50 value (measure of toxicity) for Lumbricus terrestris after 28 days is an amino acid concentration of 2% (pH 12.56) and for Daphnia it is 1.2% (pH 7).
  • The toxicity of heavy metals for soil bacteria was either enhanced or reduced depending on the amino acid used and heavy metals present.
  • The amino acid solution does not have a genotoxic impact.

More Project Information

Project title: Verbundprojekt: Zukunftsweisende Verfahrenstechniken zur Sanierung kontaminierter Böden - Teilprojekt 1: Schwermetallfixierung

Project number: 02WS0213

Project period: 2002 - 2005

Project region: Germany (Hamburg), Russia

Project contact:

Herr Prof. Dr. Westendorf

+49 (0)40 / 42883-2098

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Source: German National Library of Science and Technology Hannover (TIB)