Seasonal changes in the total mercury in small mammals in forest ecosystems near Cherepovets town, Vologda region

Mercury is one of the most dangerous environmental pollutants due to its high toxicity to animals and humans. The aim of the study was to determine the presence or absence of seasonal changes in the mercury level in small mammals in forest ecosystems near the Cherepovets town. The fur, organs and tissues of the common shrew (Sorex araneus Linnaeus, 1758) and Ural field mouse (Apodemus uralensis Pallas, 1811) were examinied during September 2020–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 the Ural field mouse varies from <0.001 (sensitivity limit of the device) in the kidneys, spleen, brain, muscles, and liver up to 0.560 mg/kg dry weight in the spleen; the average maximum THg value was found in the spleen (0.179±0.072 mg/kg) and the minimum was in the muscles (0.023±0.011 mg/kg). The content of THg in the common shrew varies from <0.001 (sensitivity limit of the device) in the brain up to 4.570 mg/kg dry weight in the fur, the average maximum THg value was found in the fur (0.754±0.152 mg/kg), and the average minimum was in the liver (0.112±0.013 mg/kg). It was established that the level of THg in common shrews was higher in winter than in summer, statistically significant differences were found for the fur, muscles, and liver (p = 0.008, 0.001, 0.033, respectively, at p < 0.05). An interspecies comparison showed differences in seasonal changes in the THg content, namely: in autumn it was higher in the common shrew than in the Ural field mouse; statistically significant differences were found for the fur, kidneys, and muscles (p = 0.005, 0.046, 0.001, respectively, at p < 0.05).