Seasonal Changes in Total Mercury in Small Mammals in Forest Ecosystems near the Town of Cherepovets, Vologda Region

Mercury is one of the most hazardous environmental pollutants due to its high toxicity to animals and humans. The purpose of this study is to determine the presence or absence of seasonal changes in the mercury level in small mammals in forest ecosystems near the town of Cherepovets. The fur, organs, and tissues of common shrew (Sorex araneus Linnaeus, 1758) and Ural field mouse (Apodemus uralensis Pallas, 1811) were examined from September 2020 to August 2021. The content of total mercury (THg) in dried samples (n = 319) was determined on a PA-915+ mercury analyzer with a PYRO console by cold vapor atomic absorption. The content of THg in Ural field mouse varies from <0.001 (sensitivity limit of the device) in the kidneys, spleen, brain, muscles, and liver to 0.560 mg/kg dry weight in the spleen; the average maximum THg value has been recorded in the spleen (0.179 ± 0.072 mg/kg) and minimum value in the muscles (0.023 ± 0.011 mg/kg). The content of THg in common shrew varies from <0.001 (sensitivity limit of the device) in the brain to 4.570 mg/kg dry weight in the fur; the average maximum THg value has been recorded in the fur (0.754 ± 0.152 mg/kg) and average minimum value in the liver (0.112 ± 0.013 mg/kg). It has been established that the level of THg in common shrew was higher in winter than in summer; statistically significant differences have been recorded for the fur, muscles, and liver (H = 9.427, p = 0.008; H = 13.828, p = 0.001; and H = 6.864, p = 0.033, respectively). An interspecies comparison has shown differences in seasonal changes in THg content: in autumn, it was higher in common shrew than in Ural field mouse; statistically significant differences have been found for the fur, kidneys, and muscles (H = 23.143, p = 0.005; H = 19.905, p = 0.046; and H = 33.418, p = 0.001, respectively).