MONITORING OF ATMOSPHERIC AND SOIL WATER COMPOSITION IN FOREST ECOSYSTEMS: MILESTONES AND OUTLOOK

The article provides an overview of Russian and foreign studies on assessment of the composition of atmospheric fallout and soil waters in forest ecosystems. The conclusion was made that little attention is given to the transformation of precipitation chemical composition by forest ecosystems, taking into account the influence of the species composition of the stand and the mosaic structure of the biogeocenosis (areas below the crowns, between the crowns, and open sites). European studies usually look at long-term development of the composition of atmospheric fallout and lysimetric waters, detecting long-term trends in composition changes of atmospheric and soil waters and identifying the factors driving these changes. In Russia, no such long-term (lasting for more than 10 years) continuous observations on the effect of man-made pollution on the composition and properties of atmospheric and soil waters were carried out. This task is very relevant for Russia and, especially, for its industrial regions.

Mercury concentrations in diverse lean fish species of the western Mediterranean

<p>The Mediterranean Sea is a water body in which the concentration of mercury is much higher than in the other world seas and oceans. Most inputs of this metal originate from the general atmospheric fallout. However, in this semi-enclosed environment there are specific sources that should be identified to understand the causes of the high toxicity by this metal. A significant proportion of Mediterranean fish devoted to human consumption is above the mercury threshold set by the European Community as suitable for human consumption. The proportion is even much larger if the recommended World Health Organization threshold is considered.</p><p> </p><p>Oily fish is known for containing mercury concentrations above these thresholds. Lean fish has been investigated in much fewer cases. The present study is devoted to this second fish type that constitutes a substantial component of human diet. Thus, the study of mercury and methylmercury in fish from local fishermen marketed in diverse Mediterranean sites has provided information on the exposure of diverse populations to this metal and has afforded a description of the Mediterranean areas that have received highest mercury spills.</p><p>1350 commercial seafood samples from the Western Mediterranean Sea were collected (Feb 2014-July 2019) in several sites such as Mallorca, Menorca, Eivissa, Alacant (Spain), Marseille (France), Genoa, Alguer, Civitavecchia (Italy). Samples from Egypt and the Atlantic Ocean (Senegal, Mauritania coasts) were also taken for comparison. Fish species were selected considering the most consumed by the population.</p><p>Comparison of the mercury concentrations in the specimens of the same fish species collected at different sites revealed where are the hot spots of introduction of the excess of this metal in comparison to the atmospheric fallout and allowed the identification of the source processes.</p><p>The fish species were grouped in three trophic levels, those feeding on plankton (first), on small fish and crustaceans (second) and on fish and cephalopods (third).</p><p>A considerable number of the analyzed fish species exceeded the maximum levels proposed by the European legislation, such as dusky grouper (100% of the examined specimens), common dentex (65%), conger (45%), common sole (38%), hake (26%) and angler (15%), among others. Representation of the Hg concentrations vs. weight of each specimen from the third trophic level showed a significant positive correlation, r = 0.78 (p < 0.01).</p><p>The average THg intake due to fish consumption, 0.61 µg/g ww, involved Hg estimated weekly intakes of 5.7 µg/kg bw for children aged 7-12 years and 4.4 µg/kg bw for adults. These values were higher than the provisional tolerable weekly intakes for total Hg intake recommended by FAO/WHO, 4 µg/kg bw, 140% and 110%, respectively.</p>

Tritium contaminated soil in sites for Semipalatinsk above-ground nuclear tests

Semipalatinsk above-ground nuclear tests caused atmospheric fallout and radioactive contam-ination of the environment that resulted in the synthesis of great amount of radioisotopes. Triti-um was the basic isotope generated in the soil as a result of above-ground nuclear tests. Previ-ously many researchers believed that tritium contamination of the soil occurred in sites for un-derground nuclear tests only. The research of tritium content in areas for above-ground nuclear tests was not taken into consideration. However, during the work in the site for above-ground tests “Experimental Field”, we examined the tritium content in soil and numerically estimated the specific activity of 3H. Because the radioisotope may be produced from the following activa-tion reactions while nuclear explosions: 6Li3 + n → 4He2 + 3Н; 10B5 + n → 24He2 + 3Н; 14N + n → 12C + 3Н, as well as 151Eu63 + n → 152Eu63 , we selected soil samples to test for 3H, as well as for 152Eu. Then analysis results were compared for establishing relationship between the isotopes and investigating the mechanism of 3H production. The article presents results of detailed study of soil contaminated with tritium in the “Experimental Field” site. 3H content in soil and the iso-tope distribution in epicenter zones of technical sites and in sites located in different distance from the epicenter are presented. Correlated dependence of the 3Н content on the 152Eu content that allowed us to discover the basic mechanism of the tritium production, that was a neutron-activation reaction occurred at the time of above-ground nuclear tests.