Patterns of mercury concentration in annual tree rings in Siberia (Russia) and the Republic of Vietnam

Relevance. The method of dendrogeochemistry makes it possible to determine the concentration of chemical elements in tree rings. As part of this work, a spatio-temporal reconstruction of mercury pollution of local and regional origin was carried out Aim. Determination of the characteristics of the Hg distribution in space and over a long time in order to identify the main factors affecting Hg accumulation by annual rings of pine, as well as the establishment and clarification of patterns in Hg accumulation in each study area. The object of the study is the core of Scots pine (Pinus syvestris L.) (Tomsk, Irkutsk regions, Republic of Buryatia) and dalat pine (Pinus dalatensis Ferré) (Socialist Republic of Vietnam). Methods. Ten cores were selected for the study in the years range from 1930 to 2022. The sampling was carried out using the Haglof age drill. The number and width of annual rings are determined with an accuracy of 0.001 mm on the LINTAB device at the Institute of Monitoring of Climatic and Ecological Systems SB RAS (Tomsk). Mercury analysis was conducted on the mercury analyzer RA-915+ by atomic absorption (pyrolysis method) on the basis of the Engineering School of Natural Resources of Tomsk Polytechnic University. Results and conclusions. The accumulation of Hg by the wood of Scots pine and Dalate pine in the studied territories is affected by natural and anthropogenic factors: natural emanations of Hg due to the degassing of the Earth's crust (Irkutsk Region and the Republic of Buryatia); local technogenesis (Tomsk Region), as well as military actions using chemical weapons (Republic of Vietnam). The study assessed the dynamics of Hg accumulation by wood over 93 years (1930–2021/2023). In the period from 1930 to the end of the 1960s there is an increased average content of the element in all the studied territories. The increased concentrations of Hg in this period on the territory of the Republic of Vietnam related to the transboundary transport of mercury from the continental part of East Asia, as well as chemical weapons used during the wars; on the territory of Russia – the growth of industrial production during the Great Patriotic War and the post-war reconstruction of the country, as well as seismicity and geological conditions.