The article presents the results of measurements of the principal ions content, electrical conductivity and pH for 13 lakes and small (temporary) water ponds in the east part of the Thala Hills, Enderby Land, East Antarctica. Water sampling was carried out by participants of the seasonal Belarusian Antarctic expeditions in the period from 2011 to 2018. The purpose of the study is the evaluation of the hydrochemical composition of lakes and temporary ponds of the Thala Hills (on an example of the Vecherny Oasis), identification of natural and anthropogenic factors which determine the variability of the hydrochemical parameters for assessment of vulnerability of lakes and temporary ponds to anthropogenic impacts and climate change. It is shown that the waters of the lakes of this region are low mineralized with the sum of ions within the range of 10.6–87.5 mg/l (the average is 34.5 mg/l), electrical conductivity — 19.3–130.0 μS/cm (61.3 μS/cm). The water is characterized as slightly acidic and neutral. The waters of small (temporary) ponds are characterized by greater variability of hydrochemical parameters in comparison with lakes: the sum of ions is in the range of 6.7–915.0 mg/l (the average is 158.0 mg/l), the electrical conductivity is 4.6–1663.0 μS/cm (the average is 267.0 μS/cm). Coefficients of variation for most compounds in the waters of temporary ponds exceed 100 %. In most cases the predominance of sodium and chloride ions was established, which indicates the influence of marine aerosols on chemical composition of water lakes and temporary ponds. Elevated concentrations of mineral elements in the water of temporary ponds are caused by the lack of flow and, and as a consequence of thies, the accumulation of salts as a result of evaporation.

Despite the great interest in the study of the chemical composition of the surface snow cover in Antarctica, the knowledge of the Enderby Land area remains extremely limited. In the Vecherny Oasis, where the construction of the Belarusian Antarctic Research Station has been carried out since 2015, the study of the chemical composition of the surface snow began in 2012 in preparation for the Comprehensive Environmental Evaluation. Its continuation is due to the need to assess the consequences of the construction and operation of the station in accordance with the requirements of the Antarctic Treaty Protocol on Environmental Protection.Snow samples were taken from 2012 to 2019 during the seasonal Belarusian Antarctic expeditions. Sampling was carried out from the surface horizons, which characterize the annual snow fallout. Chemical analytical studies were performed using standard methods. A total of 144 samples of snow water were analyzed.The aim of the study is to characterize the chemical composition of the surface snow of the Vecherny Oasis (and of the Thala Hills as a whole) to identify the areas of anthropogenic impact and trends in its change.The data on the main ions content in the surface snow, the value of pH and electrical conductivity, as well as the variabilities of the main indicators are presented. It is shown that the snow water of the Vecherny Oasis is very low-mineralized, with the sum of ions in the range of 1,04–57,3 mg/l (average — 7,4 mg/l), the values of electrical conductivity — 2,7–85,1 µS/cm (10,7 µS/cm). The snow water in most cases is characterized as slightly acidic. The chemical composition of the snow water and its mineralization is determined mainly by the content of chlorides and sodium ions. The high variability of the indicators of snow water hydrochemical composition within the areas of former and current human activities, as well as the increased content of sulfate ions, is considered to be indicative of anthropogenic impact.

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