Amendments for Rehabilitation of Soils Contaminated by Radionuclides
The Development of Composition and Technology of Amendment Production for Rehabilitation of Soils Contaminated by Radionuclides and Assessment of Their Application Efficiency
Tech Area / Field
- ENV-EHS/Environmental Health and Safety/Environment
- ENV-MRA/Modelling and Risk Assessment/Environment
- ENV-RED/Remediation and Decontamination/Environment
- OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences
8 Project completed
Senior Project Manager
Scientific & Production Association “Typhoon”, Russia, Kaluga reg., Obninsk
- Joint Institute of Energy and Nuclear Research - Sosny, Belarus, Minsk, Sosny\nKurchatov Research Center, Russia, Moscow
- Katholieke Universiteit / Department Interfasechemie, Belgium, Heverlee\nSCK-CEN, Belgium, Mol\nUS Environmental Protection Agency, USA, DC, Washington\nAtomic Energy Canada Limited, Canada, ON, Chalk River\nUtrecht University / Faculty of Geosciences, The Netherlands, Utrecht
Project summaryThe Chernobyl NPP accident caused a large-scale contamination of agricultural soils both in the Republic of Belarus, and in the Russian Federation. At present in the Republic of Belarus the total area of agricultural soils is 1,3 million hectares, and one of contaminated by 137Cs with density more than 37 kBq/m2, and also by 90Sr with density 111 kBq/m2 is 458 thousand hectares. In Russia the total area of agricultural soils is 6,7 million hectares, from which 325,0 thousand hectares of agricultural soils have levels of contamination by Cs more than 185 kBq/m2. The situation is also aggravated by the fact that a majority of the area contaminated by radionuclides comprises light texture soils with low specific sorption ability to radionuclides. Such soils are characterized by the highest accumulation coefficients of radionuclides in agricultural production. The most urgent problem is obtaining the pure produce in a private sector, where agricultural production is still conducted even at the level of soil contamination exceeding soil standards.
Currently to obtain pure standard agricultural produce in zones of radioactive contamination protective and rehabilitation measures are carried out including optimization of the physicochemical and agrochemical properties of agricultural soils by addition of enhanced doses of mineral fertilizers, liming, and organic fertilizers. These countermeasures are considered to substantially decrease the contamination of agricultural produce. However, the last data show low efficiency of the listed countermeasures considering some of them are not safe from the point of view of ecology. Thus, the problem of rehabilitation of Chernobyl-affected agricultural lands and territories is remaining one of the major problems over the next years. To successfully solve the problem it is necessary to develop and apply principally new highly efficient, economically justified, ecologically safe and technically available methods of rehabilitation.
Application of selective to radionuclides amendments on the basis of organic and mineral raw materials, including clay minerals, zeolites, sapropels, peat and etc. is very perspective agrochemical measure. The result of such countermeasures will be increasing of soil sorption ability to radionuclides and, therefore, decrease their availability to plant.
Bottom sediments of freshwater lakes or sapropels surpassing by content of organic substance (up to 90 %), nutrients and microelements many types of organic fertilizers are the special interest among such amendments. The effectiveness of sapropels is also determined by the quality of organic substance, in particular, by humic acids and nitrogen content. The maximal quantity of nitrogen reaches 4,6 % on a dry substance bases, and essential part of it is represented by aminoacids. Sapropel is an eco-safe fertilizer. The application of sapropels on soddy podzolic soils allows to reduce translocation of radionuclides from soil to plants by several times with long-term amelioration effect.
Hydrolyzed lignin (the multi-tonnage trade waste) is the material considerably increasing soils sorption ability to 90Sr. Hydrolyzed lignin is a solid residue after processing of wood or plant agricultural waste with diluted solution of sulfuric acid. It comprises lignin, some polysaccharides, resins, humic and mineral acids and ash elements. Hydrolyzed lignin as a component of different organic fertilizers has been studied for a long time. The role of lignin in formation of humus and effect of its complexion properties on nutrition of plants and increasing of their growing potential was shown in many scientific papers. Efficiency of fertilizers from hydrolyzed lignin is known to be similar to composts produced from peat. However, the majority of technically and economically efficient methods of hydrolyzed lignin utilization are not realized commercially, and considerable part of it is accumulated in waste piles, which represents an ecological hazard for the environment.
Clay-salt slimes are also promising as a possible component to amendments and organo-mineral mixtures especially taking into account their considerable stock in Belarus. The clay-salt slimes are composite materials the main components of them are carbonates of calcium and magnesium, sulfates of calcium, alumosilicates, sodium and potassium chlorides. Dolomite predominates among carbonates, anhydride predominates among calcium sulfates; aluminosilicates are mainly the clay minerals of hydromicaceous composition. The clay-salt slimes are characterized by high dispersivity and specific surface, and also considerable amount of crystalline structure defects, which increase their sorption ability. Recently conducted studies indicate the advisability of application of clay-salt slimes as amendments and structural additives on low-productive sand soils, peat bogs, and also for rehabilitation of the agricultural soils contaminated by radionuclides.
Recently, a decrease of the sulfur content in soils is observed of many countries, including Belarus. A good source of sulfur is phosphogypsum – the waste of a phosphate fertilizer production industry. Phosphogypsum is used as a meliorant for the salted and acidic soils, as the fodder additive and can be perspective as an amendment for rehabilitation of soils contaminated by radionuclides.
It is well known that the main factor, determining the 137Cs and 90Sr sorption on the soil, is the organic substance content in the soil. It is also established that the organic substance has a high capacity to form complexes with 90Sr and the clay fraction of the soil sorbs well 137Cs. Therefore, the problem of restoration of the soil physicochemical properties is of great importance for increasing of soil fertility and rehabilitation of the territories after Chernobyl accident. The raw materials mentioned above can be used for producing both amendments and organo-mineral mixtures.
Utilization of microorganisms for complete decomposition of organic and mineral substances of industrial wastes can be a perspective feature of the new industrial technology of quality amendments. Such amendments and the synthetic agricultural soils are supposed to have optimal physicochemical properties and agrochemical structure that will promote environmental recovery and increasing fertility of soils contaminated by radionuclides.
The conventional procedure of estimation of radionuclides translocation from soil into plants is based on greenhouses and field experiments and is time consuming and costly. It is necessary to point that the results strictly speaking can be applicable only for particular conditions of the experiments. Such an approach does not allow determining effectiveness of the amendment application in advance. Therefore, selection of type and dose of adsorbent is largely carried out arbitrarily and no positive effect is observed in many cases. On the other hand, on the basis of physicochemical properties of soils the methods of forecasting of biological availability and accumulation of radionuclides in plants were actively developed after the Chernobyl NPP accident. The considerable results were achieved by scientists including the participants of the project in modeling the transformation of chemical forms of radionuclides in soils. It was offered to utilize radiocaesium interception potential for the quantitative description of radiocaesium sorption in soils. These achievements were used in the works of Russian participants of the project to develop a method for estimation of radiocaesium accumulation coefficient by plants. By now this method has been successfully tested for wild-growing herbaceous plants. However, the possibility to use this method for agricultural soils and plants requires additional foundation and experimental verification. There are similar approaches to forecast accumulation of radiostrontium by plants, as well.
Thus, a modern level of knowledge about behavior of radionuclides in the “soil – plant” system gives the basis for successful development of methodology to estimate the influence of amendments on accumulation of radionuclides by agricultural plants taking into account soil properties. It will allow selecting the type and dose of amendments in particular case without carrying out long-term and expensive experiments. As a result it will be possible to use amendments economically more expediently and effectively.
The project goal is to develop the method of forecasting of amendments efficiency and the technology of production the most effective and ecologically safe amendments and organo-mineral mixtures based on natural raw material and industrial wastes.
To fulfill the project objectives it is necessary to accomplish the following tasks:
· Define kinetic and equilibrium parameters of sorption-desorption of 137Cs and 90Sr by soils, as well as agrochemical properties of soil, amendments (different types of sapropels, hydrolyzed lignin, clay-salt slimes and phosphogypsum), and their mixtures.
· Develop methods of forecasting parameters of soil-amendments mixtures using their composition.
· Develop and verify the forecasting methods of radionuclides accumulation by plants from mixtures “soil– amendment” using parameters of mixtures and biological features of plant species.
· Develop optimum compositions of amendments and organo-mineral mixtures and estimate an efficiency of their application for rehabilitation of soils in Belarus and Russia.
· Develop the production technology of amendments and organo-mineral mixtures.
Scientific findings resulted from the project realization will facilitate creating a - so far missing - scientific basis for practical execution of soil rehabilitation. It will also help to develop new effective, ecologically safe and inexpensive organomineral amendments based on stocks of organic raw material and industrial wastes promoting progress in solving important economic problems. In addition, important applied results of the project will be preparation of technical specifications and recommendation for development of amendment production, as well as opportunity to solve the problem of multi tonnage industrial wastes. The developed amendments and organo-mineral mixtures, as well as methods of their production will differ by essential novelty and originality and, therefore, will be patentable specifying commercial significance of the proposed project. In addition, the developed amendments and organo-mineral mixtures will meet standards and requirements of European Union to these products.
To achieve the project goals the participating organizations have all necessary equipment and expertise including skilled staff possessing the relevant knowledge in the field of radioecology and nuclear safety, radiation chemistry and nuclear technology, in soil science and agriculture. The specialists participated in the project will be able to apply their knowledge and experience in the field of environmental protection, especially at the time when nuclear reactors are removing from service and elimination of consequences of nuclear accidents is under way. All these correspond to the purposes and activity of ISTC.
The project will be executed in close co-operation with collaborators. They are supposed to participate in working seminars to discuss current and intermediate results of the work, to comment to the reports, to perform technical inspections of the project activities and to render assistance to the participants of the project to visit International conferences and seminars.