Humic substances are ubiquitous in terrestrial and aquatic ecosystems. Humic acids (HAs) actively interact with organic and inorganic components of lake sediments. This interaction depends on the molecular structure and elemental composition of HAs. The presented research focuses on the investigation of the composition and molecular structure of humic acids isolated from lakes located in the Lena Delta in the Russian Arctic. The findings of the research are needed to estimate the potential capacity of humic acids to bind microelements, particularly toxic metals, in stable compounds. Surface sediment samples (0–10 cm) were collected from 8 lakes by Van Veen grab during the summer period of the “Expedition LENA 2019”. We analyzed elemental composition of the HAs samples. The results showed that the studied HAs of lake sediments are characterized by low nitrogen content and prevalence of aliphatic fragments in their molecular structure. Furthermore, it was found that the studied humic acids are less mature, showing mineralization processes dominant over humification, and have relatively low potential to complexation compared with soils of the Lena Delta as well as lake sediments of territories with more boreal climate conditions.

Extremely dense fog event was studied on the 3rd December 2001, which occurred in the city of Apatity, the Kola Peninsula, northwestern Russia. Fog had low visibility (30–50 m) and lasted 17 h. Variations of atmospheric pressure and electric field before and during the fog event were measured. Multiple Taper Method (MTM) of spectral analysis has revealed pulsations of the atmospheric electric field in the frequency band of 0.007–0.05 Hz with a power-law turbulence spectrum. MTM and wavelet decomposition analysis results indicate the appearance of two types of atmospheric pressure oscillations under the fog conditions: low-frequency variations with periods of internal gravity waves and a substantial increase in pulsation intensity (more than an order of magnitude) in the high frequency (0.03–0.35 Hz) range. These results may help to improve the understanding of the microphysics of fog formation, development, and dissipation. High-frequency pulsations generation of atmospheric pressure under the fog conditions is also of interest because their period is close to the range of infrasonic oscillations, which can have negative consequences for human health.

This study presents the determination of the content of selected metals (Ba, Ca, Fe, Nb, Rb, Sr, Y, Zn, and Zr) in postglacial deposits from two glacial valleys (Ebbadalen and Elsadalen) in the Petunia Bay (southern Spitsbergen). The aim of the research was to experimentally check the usefulness of the handheld energy dispersive X-ray fluorescence technique in the study of samples from the polar zone, before performing the future field tests. Deposit analyses were performed (in parallel) with two handheld X-ray fluorescence spectrometers from different manufacturers, to investigate the accuracy and reliability of the instruments. The statistical analysis of the results indicated that the measurements carried out with two spectrometers were statistically significantly different, which was probably due to the different calibration characteristics used by the manufacturers. However, the analysis of the spatial distribution of element concentrations using Geographic Information System tools showed that the distribution maps of elements concentrations were similar regardless of the spectrometer used in the analyses.