Uranium Detection in Atmosphere
Development of an Atmosphere Monitoring Technique to Detect Technogenic Uranium
Tech Area / Field
- ENV-APC/Air Pollution and Control/Environment
- ENV-MIN/Monitoring and Instrumentation/Environment
8 Project completed
Senior Project Manager
Genisaretskaya S V
VNIIEF, Russia, N. Novgorod reg., Sarov
- Lawrence Livermore National Laboratory, USA, CA, Livermore
Project summaryThe project is devoted to verifying the technogenic uranium (U) in environmental. The aim of the project is to develop the technique based on concentration estimations of technogenic U in the atmospheric bottom layer by using the method of lichen-indication and the following solution of the inverse problem dealing with reproduction of emission source parameters. During the course of Project implementation, the emphases will be placed on studying lichen absorption mechanisms of natural and technogenic U, on developing techniques to separate natural and technogenic U in lichens as well on comparing the nature of technogenic pollutants in the atmospheric bottom layer with the levels and rates of achieving equilibrium concentrations for technogenic U in lichens. During the project implementation the methods for solving inverse problems for atmospheric pollutant transport will be developed. They will enable reproducing parameters of the emission source by using concentration values for the atmospheric bottom layer. The ubiquitous use can be made of the techniques to be developed to verify Comprehensive Test Ban Treaty (CTBT) compliance by on-site monitoring and inspection.
The atmosphere control of technogenic elements content is important for the estimation ecological situation and for the revealing of emission source. Since due to knowing the atmosphere composition and its parameters, by using models for atmospheric substance transport and methods for solving inverse problems, one can determine parameters of the emission source. Routinely, it is used standard techniques of air sampling with filters for the atmosphere control. In this case, two problems arise.
First, it is a challenging problem to arrange continuous air sampling with filters when dealing with vast territories and out-of-the-way places since there is not possible to install sampling stations and to ensure continuous operation.
Second, highly sensitive analytical techniques are needed to allow identifying technogenic pollutants against the low-background Clarke radionuclides (RN) concentrations rather than only estimating the latter.
The monitoring method for technogenic pollution of atmosphere and reproduction of emission source compliance by using lichens and the following solving of the inverse problem are proposed to develop under the Project.
The lichenoidentification method is widely used for environmental monitoring. For atmospheric control, use is made of epiphytic lichens growing on trunks and branches of trees. Lichens offer some advantages over the rest of bio-indicators due to their specific features, i.e.:
1. Epiphytic lichens absorb all elements, primarily those from the atmosphere, needed for their vital functions.
2. Lichen thallus is open 24 hours a day for elements found in the atmosphere.
3. Lichens have the value of open sorption surface 20 to 100 times higher than that of higher plants and herb.
4. Lichens are perennial plants. They are active during the entire year, have rather a stable morphology and are capable of retaining a good deal of elements in their thalluses with little damage to themselves.
5. Lichens are widely spread throughout the entire globe. They are first to occupy territories and are among the last ones to disappear under adverse conditions.
6. The researches conducted under ISTC Project № 740 revealed the ability available in lichens to separate RN of natural and man-made origin.
The enlisted distinctive features of lichens specify the prospects for their possible use and establish requirements needed for monitoring technogenic pollution of atmosphere, namely:
– method simplicity;
– availability of objects under investigation;
– wide geographic spread of objects under investigation;
– continuous communication with atmosphere and continuous accumulation of technogenic elements;
– high sensitivity of the technique;
– the ability of separate assessment of man-produced and natural elements.
By now, extensive experience has been gained to use lichens for studying atmospheric contamination with heavy metals (TM), RN as well as for mapping polluted territories. These researches were conducted in highly contaminated atmospheric environment with the percentage of elements in the atmosphere of the territory under investigation exceeding their content in the air of unpolluted areas. Therefore, the results of the said investigations cannot be used for the case when background contents of technogenic RN and when their content in the air and lichens being at the natural content level are to be controlled. The lichen-indication method for monitoring the atmospheric bottom layer to verify CTBT compliance is proposed to develop under the Project. It will be possible to use this method to verify CTBT.
To this end, mechanisms of lichen absorption of natural and technogenic RN, the dynamics of technogenic RN retention with lichens will be studied. To determine the content of technogenic RN in the air, the mathematical model of dependence between their content in the atmosphere and in lichens will be developed. To determine the parameters of the technogenic RN emission source, the mathematical model of atmospheric RN dispersion will be developed taking into account absorption of these impurities with lichens as well as the inverse problem will be solved to determine the parameters of the emission source of technogenic RN by using the data identifying their content in lichens.
The investigations are to be conducted under natural conditions in the vicinity of the contamination source and at the distance of 30 kilometers away from it, i.e., in Mordovia State natural conservation area named after P.G. Smidovich.
The work concerning application of the lichen-indication technique for environmental assessment has been conducted at RFNC-VNIIEF since 1992. The lichen-flora of the city of Sarov and that of adjacent territories was investigated. The lichens most resistant to contamination were identified. The city contamination was mapped by using biological attributes. The content of heavy metals in lichens selected within the city area and adjacent territories was estimated.
The experience of developing methods for solving inverse problems is available at RFNC-VNIIEF. The method was developed to solve the non-linear inverse problem for thermal conductivity to determine temperature dependence of the thermal conductivity coefficient. The method proposed is also applied to determine thermal characteristics of heat-insulating materials.
Currently, RN diffusion in the vicinity of the continuous emission source is being simulated under ISTC Project № 654. Within the framework of Project № 740, the research is conducted involving lichen application to assess atmospheric contamination with heavy metals, tritium and uranium. Even the first results demonstrate that epiphytic lichens feature high accumulating abilities and can be used to monitor contamination with various metals at the level of background concentrations. However, for a number of elements, the regular dependence between the elements content in lichens and in the atmosphere is complicated and determined by the nature of the absorbed element origin. To understand these regularities, absorption mechanisms of technogenic and natural elements with lichens are to be comprehended. It is also necessary to learn to identify elements of technogenic and natural origin in lichens. These researches are to be conducted under the proposed Project. While working under the Project, the earlier gained experience is to be used.
The results expected to be achieved under the Project are the following:
1. The results of studying absorption mechanisms of technogenic and natural U with lichens.
2. The data on the dynamics of accumulating technogenic U with lichens.
3. Separation techniques and analytical methods for assessing technogenic and natural U absorbed by lichens.
4. The mathematical model of dependence between the technogenic U content in the atmosphere and in lichens.
5. The mathematical model of technogenic U dispersion in the atmosphere taking into account transition of these impurities into lichens.
6. Developing methods for solving the inverse problem to determine source parameters of tecnogenic RN emission by using the data on their content in lichens.
The practical results expected to be achieved under the Project will include methods and approaches developed to monitor technogenic pollution of atmosphere and to reproduction of emission source parameters. It will be possible to use this method for CTBT compliance and to reveal non-declared activities by using lichen-indication methods.
Project implementation will make it possible to redirect the efforts of 43 high-skilled specialists from developing nuclear weapons to solving the problems of verifying the agreement and controlling non-declared activities. The major personnel include 4 doctors of sciences, 8 candidates of sciences. The specialists from St. Petersburg University are to take part in the work under the Project.
Foreign collaborators are needed to assist in commercialization of results, to participate in joint experiments as well as to exchange information on approaches and methods, to hold joint workshops.
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