Poplar tree (Populus balsamifera L.) as indicator of mercury emission from a point source.

The article provides original data on the ecological and geochemical characteristics of the distribution of Hg in the leaves and annual rings of balsam poplar (P. balsamifera L.) in the zone of influence of lithium production (Novosibirsk). In 2017 high Hg concentration (1300 ng/g) in the poplar leaves was recorded in the northeastern part of the city near the industrial facility of the lithium plant. The investigation showed a clear trend of increased Hg accumulation in the poplar leaves during the growing season. The maximum average Hg content was detected in the leaf litter in 2006 (1153-2425 ng/g). However, the average Hg content in the soil is 294 ng/g, which is significantly lower than the threshold limit value (2100 ng/g). Studies of changes in the content of Hg with the height of the crown of the tree revealed an increase in the upwind side of the emission source, the concentration of Hg in the leaves is on average 1.5 times higher than on the side of the "wind shadow". Hg in poplar leaves, leaf litter, and soils is mainly found in free and physically bonded forms - the most mobile, prone to increased migration, transformation and methylation under environmental conditions. According to the Hg content in the poplar cores, an increase in the Hg input near the source was established with the beginning of Li production - in the period 1967-1985 years (441 ng/g) with a subsequent decrease to 6 ng/g in 2000-2017.

Landscape REE anomalies and the cause of geophagy in wild animals at kudurs (mineral salt licks) in the Sikhote-Alin (Primorsky Krai, Russia).

To test the "rare earth" hypothesis of geophagy, geological and hydrogeochemical studies unparalleled anywhere in the world were carried out at kudurs (salt licks) in two districts in the Primorsky Krai, Russia. The mineral and chemical compositions of geophagic earth consumed by animals, the chemical composition of surface waters and vegetation, and the chemical composition of biological tissues of red deer (Cervus elaphus) were studied in this research. It was found that ultra-fresh surface and fontinal waters in the studied areas contain anomalously high concentrations of rare earth elements (REE), the sums of which exceeded the average values in the Primorsky Krai and worldwide by tenfold, and more. The presence of landscape REE anomalies is confirmed by elevated concentrations of these elements in vegetation. Using electron microscopy, it was determined that the sources of REE in landscape components are rocks containing secondary, readily soluble, REE minerals (hydrophosphates and fluorocarbonates). The study of the chemical composition of animal tissues showed the presence of significant concentrations of heavy REE (HREE) in the blood and brain, which indirectly indicates a high probability of animals developing stress reactions against the background REE-elementosis. Eaten earthy substances in both areas are represented by mixtures of smectite clays and zeolites with high ion-exchange properties. In the digestive tract of animals, such sorbents actively interact with the biological electrolyte, saturating it with sodium ions and absorbing HREE. The main meaning of geophagy is regulation of the concentration and proportion of REE in the body. Sometimes it manifests itself in intake of significant amounts of Na.