Estimation of 90Sr content in Scots pine timber based on measurement of beta particle flux density from the surface of the trunk bark

The measurement of the 90Sr content in the components of forest ecosystems using radiochemical methods requires considerable time and effort to obtain output results. A less precise, albeit quick, assessment of this radionuclide at the stage of field work can considerably accelerate the decision-making on the possibility of involving a certain forest plot in experimental work or using it for economic purposes. Ukrainian and foreign scientific groups often devote publications to similar express methods for determining the content of biologically mobile radionuclides (137Cs and 90Sr): specific activity, pollution density, etc., since they allow considerably reducing the amount of field and laboratory work. Proceeding from collected field materials from 13 experimental plots of pure pine stands, close (r=0.85-0.94) statistically significant relationships at p=0.05 were found between the specific activity of 90Sr in stem wood and the results of measuring the density of beta flow with a radiometer from the surface of the bark of Scots pine tree trunks at breast height (1.3 m) within a 10 km zone around the Chornobyl NPP. Direct, linear relationships were established between the average content of 90Sr in the anatomical parts of tree trunks of pine stands (sap, core, and all wood) and the surface density of the flow of beta particles from the bark of trees, which were used to create regression equations suitable for preliminary assessment of the specific activity of the radioisotope under study in timber in the field conditions (R2=0.90-0.96). A close correlation (r=0.93) was found between the average stand diameter and the concentration ratio of 90Sr in sapwood to the specific activity of radionuclide in the core wood of trunks. The dependence of the 90Sr content on the density of the flow of beta particles from the surface of the bark of tree trunks was established, and the ratio of the specific activity of this radionuclide between the sapwood and the core can be recommended as a method for rapid measurement of 90Sr in Scots pine wood. However, given the small sample size and the importance of the issue under study, it is necessary to continue working in this area with an increase in the number of empirical data for pine stands, as well as attracting observations of other major forest-forming tree species in the exclusion zone