Mercury Emanations from the Baikal Rift: Evidence from the Study of Annual Tree Rings (an Example of the Tunka Depression)

摘要

The phenomenon of natural degassing of mercury in the Baikal Rift Zone is considered on the basis of study of the annual rings of poplar ( Populus suaveolens Fisch.) and pine ( Pinus sylvestris L.) trees. Tree core samples were collected in the Tunka Depression in July 2018 using a drill. The boundaries of the annual rings were highlighted on a LINTAB instrument with TSAP-Win and Lignovision software. Analysis of Hg was performed on a RA-915M mercury analyzer by pyrolysis. The dynamics of changes in the concentration of Hg in the annual rings of poplar and pine trees in the Tunka Depression from 1940 to 2018 was studied. The average Hg content in all wood cores examined was 7 ppb with a maximum of 1089 ppb. The high Hg contents are confined to faults of both sublatitudinal and northwestern striking. The maximum concentration of Hg was detected in pine and poplar cores at the intersection of large tectonic faults. A relationship between the peaks of high Hg concentrations of in wood and periods of strong earthquakes with a magnitude of 4.0 was revealed. The data obtained may be paleoindicators of deformations of the Earth’s crust, recording both individual processes of short-term relaxation of tectonic stresses and the earthquakes themselves.