HEAVY METALS AND ARSENIC IN SOILS IN THE VICINITY OF INDUSTRIAL ENTERPRISES AND NUCLEAR POWER PLANT (BY THE EXAMPLE OF THE BELOYARSK NPP)

Abstract

The relevance. Pollution of ecosystems with heavy metals and arsenic is a significant anthropogenic factor that adversely affects humans and biota. In the Sverdlovsk region, where mining and processing of mineral raw materials is carried out, high levels of pollutant emissions from stationary sources, including heavy metals, are noted. The region is also characterized by multicomponent contamination of territories with artificial radionuclides. Since 1964, the Beloyarsk NPP has been in operation in the Sverdlovsk region. The long-term operation of industrial enterprises and radiation hazardous facilities increases the technogenic load on the ecosystems of the Urals. The main aim of the research is to assess the content of heavy metals and arsenic in the soils of terrestrial ecosystems in the vicinity of industrial enterprises and the Beloyarsk NPP based on environmental monitoring. Objects. In 2013 and 2019 the soils of natural (meadow) and agricultural (arable land, grassland) ecosystems of the 30-km zone of influence of the Beloyarsk NPP were studied. The content of 17 elements related to I (Pb, Zn, Cd, As, Hg), II (Mo, Cu, Ni, Co, Cr, Sb), III (Sr, Mn, V, W, Ba) hazard classes was studied in the soil cover, as well as iron. Methods. The assessment of the total content of heavy metals and arsenic in the soil was carried out in the testing laboratory of agroecology of the RIRAE (accreditation certificate RA.RU.513078). To prepare soil samples for measurements, we used the methods of «cold vapor» and «wet ashing» with a MARS-5 microwave system (CEM, USA). The elements in the samples were determined by atomic absorption and plasma emission methods of analysis. For measurements, we used an axial atomic emission (optical) spectrometer with sample atomization in inductively coupled plasma (ICP–OES) Liberty II (Varian, Australia–USA) and a KVANT spectrometer Zeta-1 with the GRG-3. Results. It is shown that for 2013−2019 the ratio of elements in the soil cover of terrestrial ecosystems in the vicinity of the Beloyarsk NPP was quite stable. According to the decrease in the total content in the soil, heavy metals and arsenic in 2019 were arranged in the following order: Fe (average − 16700 mg/kg)>Mn (879)>Ba (134)>Zn (51)>Ni (35)≥Cr ( 32)≥V (30)≥Sr (28)>Cu (21)>Pb (12,4)≥Co (11,9)>W (6,7)>Sb (2,4)>As (1,7)≥Mo (1,5)>Cd (0,2)>Hg (0,01 mg/kg). According to the total accumulation of elements in the soil, terrestrial ecosystems are in the ratio: arable land (18,7 g/kg of soil)>meadows (14,9 g/kg)>virgin land (12,6 g/kg). Such a distinction is due to differences in the content of iron in the soil, the contribution of which to the regional background is 90…95 %. A weak correlation between the content of elements in the soil and the distance from the Beloyarsk NPP (–0,44...0,29 in 2013 and –0,29...0,38 in 2019) showed the absence of significant emissions of toxicants into the environment from the nuclear power plant both as a result of its many years of work, and after the start of operation of the BN-800 reactor. Among the I hazard class pollutants accumulated in the soil, zinc dominates (contribution 76…78 %), lead is in second place (18...21 %). In II hazard class, the main soil pollutants are nickel (45…34 %) and chromium (28…30 %). In III hazard class is dominated by manganese (68...81 %) and barium (14...27 %). It is shown that in 25…63 % of soil samples in the vicinity of the Beloyarsk NPP, the gross nickel content does not correspond to the approximate permissible concentrations established in SanPiN 1.2.3685−21. In addition, in all control plots of meadow ecosystems, the maximum permissible concentration for the content of antimony was exceeded. In 2019, in 4…25 % of soil samples of arable land and meadows, a discrepancy was noted with maximum permissible concentration for manganese, and in 4…11 % of soil samples of arable land, the maximum permissible concentration for arsenic was exceeded. The levels of accumulation in the soil of a number of heavy metals also exceed the regional background of the Sverdlovsk region: for nickel in 25...63 % of soil samples of natural and agricultural ecosystems, for manganese in 10...50 % of soil samples of arable land and meadows. The greatest amount of elements (average 42 %) is accumulated in the 0−5 cm soil layer. The maximum accumulation in the upper soil horizon was noted for cadmium (62 %), arsenic (49 %), and lead (48 %), and the minimum for antimony (29 %) and manganese (28 %). According to the total stock of toxicants in the 0−5 cm soil layer, they are arranged in a row: Cd>As>Pb>Zn>Cu>Mo>Hg>Sr>Ni>Cr>V>W>Co>Ba>Sb>Mn. In deeper horizons (5−10, 10−15 and 15−20 cm) of soil the elements are distributed evenly. Compared to other technogenically-polluted regions of Russia, the results of monitoring the content of heavy metals and arsenic in the soil of the Beloyarsk NPP area show a stable ecological situation. When planning further monitoring studies, it is necessary to pay attention to the behavior of arsenic, nickel, antimony, manganese, cadmium and lead in the soil. The increased content of these toxicants in the soil can lead to their accumulation in agricultural and natural food products.

Keywords

• terrestrial ecosystems
• soil cover
• anthropogenic impact
• pollutants
• technogenic contamination
• environmental monitoring
• hygienic assessment
• environmental safety