Humates NATO ARW Home Page

NATO Advanced Research Workshop

Use of humates to remediate polluted environments:

From theory to practice

Zvenigorod, Russia, September 23-29, 2002

Scientific abstract
Advanced Research Workshop

Title of Meeting

Use of humates to remediate polluted environments: from theory to practice

Name and affiliation of Co-Directors:

NATO-country Co-director

Hertkorn, Norbert, Dr., Research Scientist, Institute of Ecological Chemistry, Research Center for Environment Protection and Health (IOEC GSF), Neuherberg, Germany

Partner-country Co-director

Perminova, Irina V., PD Dr., Senior Scientist, Department of Chemistry, Division of Organic Chemistry, Lomonosov Moscow State University, Moscow, Russia.

Scientific Content

To meet the demands of the 21st century, modern remediation strategies will have to rely upon natural processes governing the transformation and transport of chemicals which had been released into environment. The technologies that show considerable promise at this stage, from both technological and economical viewpoints, involve the use of humic substances. Humic substances are ubiquitous in the environment and comprise the most abundant pool of non-living organic matter. The resources of humic and humic-like substances containing materials are immense. They consist of lignites, brown coal, peat, lake bottom sediments, composts, biohumus, etc. The peculiar feature of humic substances is polyfunctionality, which results from the presence in their structure of both hydrophobic aromatic core highly substituted with functional groups and of hydrophilic (oligosaccharidic and oligopeptidic) units. As a result, humic substances can interact both with heavy metals and organic contaminants impacting greatly their fate in the environment. The mediating impacts of HS in the polluted environments can be defined as follows:

impact on speciation of heavy metals and organic xenobiotica;
impact on interphase partitioning of the ecotoxicants,
impact on the abiotic and biotic transformation of the ecotoxicants,
impact on physiological state of living organisms under conditions of the polluted environments.

The above concept of the mediating effects of humic substances determined the following key issues of the NATO ARW: (1) to evaluate the use of humic substances as one of the most prospective and most effective natural tools for the mitigation of the impacts of ecotoxicants on living organisms and (2) to assess strategies to develop environmentally sound humates based remediation techniques applicable for aerobic and anaerobic conditions. To reach the given goals, the ARW participants were spread among three working groups. The first group was focused on consideration of the binding and detoxifying properties of humics in the homogeneous systems, the second group - on the sorptive-desorptive interactions in the heterogeneous system: minerals - humics- ecotoxicants, and the third group - on the redox mediating properties and biological activity of humic substances. As a result of the very intense and fruitful discussions during the concluding round table, the working groups agreed on the following implications of humics for remediation technologies:

binding agents (detoxicants) aimed to reduce the bioavailability, and thereby the (eco)toxicity, of inorganic and organic contaminants,
sorbents aimed at construction of permeable reactive barriers to immobilize hydrophobic organic contaminants and heavy metals released into aquifers,
flushing agents aimed at mobilization of organic contaminants tightly bound to mineral particles in aquifer,
redox mediators aimed at catalysis of abiotic and biotic oxidation/reduction of chlorinated and petroleum hydrocarbons,
adaptogens and carriers of nutritional elements for plants aimed at an increase of the plant resistance to the influence of stress-factors.

The joint discussion of the scientists, remediation engineers, and producers of commercial humates allowed to formulate the key research needs to promote humates use on the market of remediation technologies. As those were allocated the following tasks:

to elaborate quantitative criteria and define proper tools to certify the quality of humics based products. The quantitative criteria should relate to composition (elemental, structural groups, molecular weight), molecular structures, bulk properties relevant to the use of humics for remediation purposes (ion-exchange capacity, amount of strong and weak acidic groups, charge to mass ratio, hydrophobicity, binding affinity and sorption capacity for heavy metals and organic xenobiotica, sorption affinity for mineral surfaces, redox potential, solubility of metal complexes formed) as well as the biological activity of humics (fertilizing effects, biochemical effects on living organisms on different levels of organization, toxicological properties).
to develop new humics based products of much higher specific activity using the directed chemical modification and fractionation techniques;
to demonstrate a potential of humics based remediation technologies by planning and realizing the corresponding experiments on the pilot and field scale.

Humates NATO ARW Home Page