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• Hg contents in different types of Antarctic soils showed a large variation. • Soil Hg was found to be closely related to organic carbon (OC). • Relationships between Hg and OC allow to identify soil affected by enhanced Hg inputs. Antarctica is a sink for mercury (Hg) and plays an important role in the global Hg cycle. Knowledge about the environmental fate of Hg in Antarctic terrestrial ecosystems, however, remains highly restricted. In this study, we investigated soil Hg in samples from three areas located across a wide latitudinal range from about 62°S to over 74°S with very different climatic and environmental conditions and different potential (natural and anthropogenic) sources of Hg. The highest Hg levels were found in soils beneath mosses and ornithogenic soils in the Antarctic Peninsula, whereas extremely low values were found in coastal East Antarctica. Total Hg concentrations in soil samples from the three study areas were always closely related to those of organic carbon (OC). In corroborating the results of previous studies, this large-scale survey strongly suggests that OC is a dominant driver affecting Hg distribution in Antarctic soils. The observed linear relationship between Hg and OC concentrations, also supported by available literature data, probably, has a general relevance for Antarctic soils, and allows to identify samples affected by enhanced Hg deposition from anthropogenic or natural sources. In providing a better understanding of the biogeochemical cycle of Hg in Antarctic terrestrial ecosystems, this study suggests that soil OC content must be considered to assess Hg distribution patterns in Antarctic soils. In samples (including those of lacustrine sediments, planktonic, and benthic algal mats) unaffected by an accentuated deposition of Hg, the value of the ratio [Hg ng/g]/[OC %] appears to be less than ∼ 11. [ABSTRACT FROM AUTHOR]

• Atmospherically formed ClO 4 − is the primary source for soil in Antarctica. • Inputs from humans and wildlife to ClO 4 − in Antarctic soil are rather minor. • Leaching by snow meltwater may be the main sink for ClO 4 − in Antarctic surface soil. • Biological reduction may be not an important sink for ClO 4 − in Antarctic surface soil. Perchlorate (ClO 4 −), a persistent inorganic compound, has harmful effects on human health. Natural ClO 4 − is formed in the atmosphere and enters into the surface environment through deposition. However, the knowledge on the occurrence, spatial variability and sinks of natural ClO 4 − in different environments remains limited, especially in the polar regions. Here, we investigate the sources and sinks of ClO 4 − in soil collected in three ice-free areas in coastal Antarctica, where the research stations and wildlife colonies are mainly distributed. No statistically significant difference in ClO 4 − concentrations between sites near and away from the stations suggests that local human presence is not a significant source of ClO 4 − in soil. Concentrations of ClO 4 − in soil from wildlife colonies are not significantly higher than those from sites with no intense wildlife activities, indicating that wildlife activities have no significant influences on ClO 4 − in soil. Thus, atmospherically formed ClO 4 − is the main source for soil in Antarctica. In general, ClO 4 − concentrations (0.1–5.1 μg kg−1) in soil in this study are much lower than those in the arid environments and comparable to those in the unsaturated zones. Leaching by snow meltwater may be the main sink for ClO 4 − in soil, and deeper depths for aqueous migration may contribute to the lower ClO 4 − concentrations in Antarctic surface soil compared to the values in the arid areas with low precipitation amount. Due to the biological origin of NO 3 −, no correlation between NO 3 − and ClO 4 − in soil is observed in this study, different from the observations in arid areas. In addition, no significant correlation is observed between organic matter contents and ClO 4 − concentrations in soil, suggesting that biological reduction is not an important sink for ClO 4 − in Antarctic soil. [ABSTRACT FROM AUTHOR]