METHOD FOR EVALUATION OF CAESIUM-137 SPECIFIC ACTIVITY IN FOREST PLANT RESOURCES Russian patent published in 2014 - IPC G01N33/24 

FIELD: agricultural industry.

SUBSTANCE: invention relates to the ecology field and is intended for forest territories radioecological monitoring and plant resources radiation control under technogenic radioactive contamination conditions. The method involves sample plots identification, soil and forest vegetation sample batches collection, samples preparation, measurement of specific activity in the collected sample batches, evaluation of soil contamination density and coefficient of radionuclides transition from soil into vegetation. At the preliminary stage one creates a local radioecological base consisting of coefficients of caesium -137 radionuclides transition from soil into certain types of plant resources and correction coefficients for results of field measurements of soil contamination density with a portable spectrometer (the results depending on technogenic caesium distribution character in the soil profile and soil properties) by way of sample plots identification taking into account the list of commercially valuable plant resources types, forest vegetation conditions types and area occupied by the said conditions within the region territory. One performs evaluation of spatial nonuniformity of soil contamination with caesium -137 within the sample plot with the portable gamma spectrometer by way of road survey with the produced results geographical reference. One determines correction coefficients within sites uniform in terms of degree of contaminations and forest vegetation conditions of the sites with the help of identification of survey points with the portable spectrometer for evaluation of soil contamination with caesium -137 in the field environment (P_scan) with further collection of soil sample batches with a standard cylindrical sample selection device at depth equal to 20 cm with division of soil cores into 5 cm layers for laboratory gamma-ray spectrometry measurements for evaluation of contamination density (P_lab) and caesium -137 distribution across the soil profile in laboratory conditions. The correction coefficients equal to the ratio of P_lab/P_scan are determined according to the following algorithm. Across all the points of the region sample plots, a diagram of P_lab/P_scan values dependency on the fraction of caesium -137 content in a 0-5 cm layer of soil of the total content in a 0-20 cm layer (x, %) is constructed. The equation of P_lab/P_scan dependency on x and the equation coefficients values are determined by a regression analysis method. The transition coefficients are evaluated within uniform sites in a characteristic period of the resource procurement. At the main stage, evaluation of caesium -137 specific activity in plant resources on certain forest use sites is performed according to data of field measurement of density of soil contamination with caesium -137 with the portable gamma spectrometer by way of road survey and specific activity calculation based on combination of the field measurements base with forest mensuration data with usage of radioecological base coefficients for certain forest vegetation conditions and plant resources types specific to them.

EFFECT: proposed invention usage enhances credibility of evaluation of specific activity of plant resources (quality in terms of radiation feature), the possibility of resources quality forecast by the radiation feature and simultaneous evaluation of the whole spectrum of forest resources of the site investigated as well as reduction of the total time of measuring apparatus operation.

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