The Level of Snow Cover Contamination with Fluoride Compounds in the Emission Zone of a Primary Aluminum Smelter

Background: Fluoride compounds are one of the main components of industrial emissions from aluminum production. Natural deposition of fluorides with precipitation leads to their accumulation in soil and surface waters. In winter, the snow cover enables an assessment of industrial pollution with fluoride compounds. The objective of our work was to study fluoride levels in the snow cover in the emission zone of the primary aluminum smelter in the town of Shelekhov, Irkutsk Region. Materials and methods: Snow sampling was performed at nine points at different distances from the plant and fluoride concentrations were then measured in the aqueous fraction and solid precipitate by a potentiometric method with ion-selective electrode. Results: The aqueous fraction was a solution of hydrofluoride and sodium fluoride. Insoluble fluorides were found as a mixture of aluminum fluoride, calcium fluoride, cryolite, and aluminum tetrafluoride. We established that the soluble fraction exceeded 90 % in all snow samples. Within the urban agglomeration, snow pollution was distributed differentially. The total fluoride level in residential areas of Shelekhov was 14 to 21 times higher than that at the reference point. At the same time, in the area of a suburban rural settlement located downwind of the smelter, it reached a 33-fold excess. Conclusion: The main source of environmental pollution in the Shelekhovsky district of the Irkutsk Region is the processing of cryolite and fluoride salts in the primary aluminum production technological cycle generating fluorine-containing gaseous emissions and solid wastes. Concentrations of industrial pollutants in snow correlated with the distance from the source of emissions and the prevailing wind directions. Contribution of a heat power engineering enterprise to the industrial pollution of the local environment with fluorides was also revealed.

ACTIVITY AND ISOZYME COMPOSITION OF PEROXIDASE IN SCOTS PINE (PINUS SYLVESTRIS L.) NEEDLES EFFECTED BY TECHNOGENIC EMISSIONS FROM VARIOUS ENTERPRISES AND VEHICLES

Background. The technogenic pollution leads to excessive production of reactive oxygen species (ROS) in plants which are highly reactive and toxic and cause damage to biomolecules. Plants have a complex antioxidant defense system that protects cells from the ROS and maintain homeostasis. The most important link this system is enzymes, in particular, peroxidase. It was of interest to determine the expression of the protective properties of one of the sensitive species of coniferous plants under the influence of technogenic emissions from various enterprises and vehicles. Purpose. Investigation the activity and isoenzyme composition of peroxidase in the needles of Pinus sylvestris L. under the influence of technogenic emissions of different compositions in the Baikal region. Materials and methods. The pine needles were collected on sample plots located near an aluminum plant, thermal power plant, chemical plant, coal mining enterprise, and the highway. The activity of soluble guaiacol-dependent peroxidases was defined by spectrophotometry in a reaction mixture with citrate-phosphate buffer, hydrogen peroxide, and guaiacol. Native polyacrylamide gel electrophoresis was used for determination of peroxidase isoforms. Results. It was shown that an increase in the total guaiacol-dependent peroxidase activity ranged from 6 to 22 times in the pine needles in polluted areas. Maximum enzyme activity was found in needle samples collected near the aluminum smelter, whose emissions are characterized by large amounts of fluorides and polycyclic aromatic hydrocarbons. The high variability of peroxidase isoform composition in Scots pine needles under industrial pollution was revealed. It was expressed in the emergence of new isoforms in the zone of fast-moving (Rf from 61 to 100) and medium-moving (Rf from 31 to 60) items. The maximum number of isoforms (nine) was found in pine needles near the aluminum smelter with only two ones detected in the background area. Conclusion. Peroxidase activity and the number of its newly formed isoforms can adequately reflect the degree of technogenic pollution and trees decline. The indicators can also be used in monitoring of coniferous forests condition.

Fluoride Exposure and the Effect of Tobacco Smoking on Urinary Fluoride Levels in Primary Aluminum Workers

Workers in primary aluminum smelter are exposed to fluoride from cryolite (Na3AlF6) used in the electrolysis process. Post-shift urinary fluoride is considered as an appropriate index for examination of fluoride exposure. The objective of the study was to investigate the exposure to fluoride in primary aluminum smelter in Žiar nad Hronom (Slovakia) during three consecutive two-year periods between 2012 and 2018. The relationship between fluoride exposure in the occupational environment, tobacco smoking, and pre- and post-shift urinary fluoride concentration was investigated in 76 male workers in the ages from 21 to 60 years. Workers were monitored by personal fluoride sampling equipment. Their urinary samples were collected prior to the start and at the end of an eight-hour shift. Fluoride content in urine samples was analyzed by potentiometric ion-selective electrode and expressed as weight ratio of fluoride content to creatinine. The Mean ± SD particulate fluoride concentration in occupational air was 0.966 ± 1.658 mg/m3 and gas-phase fluoride concentration was 0.327 ± 0.809 mg/m3. Mean urinary fluoride concentration of all workers was significantly higher (p < 0.001) after the eight-hour shift. Smokers tended to have a higher post-shift mean urinary fluoride concentration than non-smokers, but this difference was not statistically significant (p = 0.11). The difference between these two groups of workers was also not statistically significant (p = 0.62) before the shift. Therefore, according to results, smoking caused no statistically significant difference in urinary fluoride levels between the group of smokers and group of non-smokers in primary aluminum workers.