The goal of this project is to develop and use polymeric technology based on non-stoichimetric interpolyelectrolyte complexes (NIPECs) with an excess of an anionic polymer, both synthetic and natural (humic substances). Negatively charged NIPECs will be able to bind to cationic colloidal particles and keep the binding even being electrostatically pre-complexed with heavy metal cations. Thus, use of NIPECs will allow to solve two interrelated problems: extraction and concentration of heavy metals and prevention of their spread by means of wind and water erosion.
During the Soviet period, discharges of radioactive elements resulting from uranium mining industry in the environment were a common practice and, as a result, more than 80 contaminated sites are accounted for in the Republic. Although uranium processing is no longer practiced in Kyrgyzstan, a large number of open landfills and uranium ore storages still remain abandoned at the vicinity of these settlements. These neglected sites have enormous problems associated with soil erosion and known as “technogenic deserts”. The upper soil horizons are deprived of humus and vegetation, which favor the formation of low-buffer landscapes in the zones of maximum contamination. As a result, most of these areas are not re-cultivated and remain in critical environmental conditions. The Kyrgyz Republic is located in an active seismic zone, thus status quo poses imminent threats for natural disasters including contamination of large territories due to the possibility of earthquakes, landslides and mud-torrents in these areas. We will focus on technogenic area of Kyrgyzstan nearby Kara-Balta ore-dressing plant and Kadzhi-Say uranium technogenic province. The contaminated areas within the technogenic zones clearly have radiation levels well above background. The critical features of this place are: highly degraded soils are featuring the current state of local ecosystem. Sandy winds are usually spreading out the material of uranium tailing’s cover in different directions the site, while extensive water erosion through temporary drains are exporting contaminated materials northward down to the direction of the Lake of Issyk- Kul for Kadzhi-Say area.
Both the fundamental research data and practical application of polymeric binders, i.e. non-stoichimetric interpolyelctrolyte complexes (NIPECs) demonstrated that NIPECs are effectively bound to soil particles and cannot be washed away with rainfall, or artificial irrigation, or water from melted snow. Additionally, NIPECs are able to bind effectively a majority of toxic metals due to incorporation of metals inside hydrophobic NIPEC fragments generated by mutually neutralized cationic and anionic units. As a result, thermodynamically stable structures are formed with a central metal ion surrounded by functional groups of both polyelectrolytes. This approach ensures formation of stable grass covering in a shortest period of time which prevents wind and water erosion and suppresses spread of heavy metals. After completing the protection function, the formulation is destructed, being affected by soil microorganisms, and transformed down to simple non-toxic substances that will improve the environment.
For the development of NIPECs it was rather prospective to use humic substances, natural ecologically safe de-toxicants of complex effect. It is so, because humic substances comprise the properties of (1) reclaiming agents – favourably influence on physical and chemical properties of soil by their structuring, increasing moisture capacity, improving gas exchange, etc., (2) sorbents- bind hydrophobic organic compounds as physical sorption mechanism, and ions of metals – as ion exchange mechanism, (3) antidotes- enter into chemical reactions with a wide range as well as organic and inorganic compounds. Soil, enriched with humic substances, can endure significantly higher technogenic loads. Protective effect of humic substances is explained by the formation of non-toxic and inaccessible for live organisms complexes with eco-toxicants.. The prospects of practical application of humic substances as de-toxicants is specified by large resources of humus-containing materials, such as brown coal, peat, sapropel and other caustobiolites.
Developed technique based on polymer complexes will be trialed.
In order to achieve our goals, the following tasks need to be solved:1. To map the respective watershed and build its 3D dynamic model, characterizing water and wind erosion of the area under various weather conditions and in mid and long term climate change conditions; to research and map the all surface drains and the aquafer and describe the behavior of surface and underground water and to develop the inventory of micro watersheds, landscapes, ecosystems, soils and vegetation;
2. To build spatial scenarios of the use of the site and its surroundings and the outlook of the contamination and its impact features in mid and long term future.
3. To characterize the physical-chemical parameters of soils in terms of historical data about land use; mineralogical parameters, structural soil features, basic chemical and organic matter content;
4. To study polycation-to-humics binding to heavy metal and radionuclides cations and soi) particles,
5. To study binding of NIPEC-metal ternary complexes to soil particles,
6. To estimate protective properties of polymeric formulations,
7. To perform field testing of produced formulations for stabilization and detoxication of contaminated soils;
8. To carry out quality control of methods in terms of soil erosion, detoxifying ability.
The proposed technology has no world analogs. Specifically new point is the development and optimization of the technologies based on humic substances which have demonstrated detoxication and sorption levels well above synthetic analogs by the indices of efficacy of their detoxification effect with respect to heavy metals and uranium ions.
