Mikhail V. Pastukhov

This study evaluates the impact of the sludge impoundments at the Solzan site of the former Baikal Pulp and Paper Mill at Lake Baikal on soil chemistry. Concentrations of 16 elements were analyzed in the surface soil layer both near and at a distance from the sludge impoundments. Chemical analysis was performed using atomic absorption spectrometry. The results showed that, based on the coefficient of variation (CV), element concentrations in soils near the impoundments exhibited moderate (29–49%) variability for Al, V, Cd, Cr, Pb, Ca, and Ni; high (53–68%) for Sr, Mn, Co, Mg, Fe, and As; and extreme (109–317%) for Cu, Hg, and Zn. At a distance from the impoundments, the variability was substantially lower: Al (19%); V, Mn, Fe, Pb, Cr, Mg, Cd, Co, and Ni (24–48%); Ca, Sr, Hg, Cu, and As (50–90%); and Zn (121%). The level of anthropogenic impact was assessed using contamination indices calculated relative to the local reference levels. According to the contamination factor (CF), most of the samples exhibited low to moderate contamination. However, localized significant (Co, As, Hg, Cu, Pb) and very high (Zn, As, Cu, Hg) contamination was recorded near the impoundments, as well as significant (Cu, As, Sr) and very high (As, Zn) contamination at a distance. The pollution load index (PLI) indicated multi-element contamination in some samples, both near and at a distance from the impoundments. The enrichment factor (EF) suggested minimal to moderate enrichment for most of the samples. Nevertheless, individual samples exhibited significant (Cr, Co, V, Ni, Zn, Cd, Al, Pb, Hg, As, Cu), very high (Hg), and extremely high (As) enrichment near the impoundments, as well as significant enrichment (Cu, Zn, As) at a distance. These findings expand the theoretical understanding of element distribution, accumulation, and migration patterns in environmental compartments during the post-operational phase of major industrial contamination sources. Furthermore, they hold practical significance for planning future reclamation and environmental protection measures.

Large-scale environmental contamination caused by the Baikal Pulp and Paper Plant and its industrial waste determines the relevance of studying the chemical composition of abiotic and biotic components in the impact area of the anthropogenic source. The aim of the research is to investigate the chemical composition and assess the level of soil contamination in the Solzan landfill and adjacent areas, including the coastal area of Lake Baikal. The study has determined the concentrations of Hg, As, Pb, Cu, Zn, Co, Ni, Cr, Mn, Sr, Ba, Rb, and TOC (total organic carbon) in soils near and far from the lignin sludge storage cell in the Solzan landfill. The obtained results show an extremely uneven distribution of elements across the study area. Abnormal element concentrations exceeding Clarke values, regional background concentrations, and soil sanitary and hygienic assessment criteria have been revealed near the lignin sludge storage cell. The uneven distribution of elements, high organic matter content, and wide range of pH values in the soils indicate an anthropogenic transformation of their chemical composition. The concentration of chemical elements in the soil decreases with distance from the impact area. Widespread soil contamination with zinc has been identified, with concentrations exceeding regional background levels and sanitary and hygienic standards both near and far from the source of contamination. According to the total pollution index, anthropogenically transformed soils in the study area mainly have an acceptable level of contamination. Nevertheless, moderately hazardous and hazardous levels of soil contamination have been detected both near and far from the Solzan landfill.

The morphological peculiarities of receptor neurons and support cells in the olfactory epithelium of male yellowfin sculpin (Cottocomephorus grewingkii; Dybowski, 1874) were studied during the pre-spawning, spawning (when males do not feed and have a higher sensitivity to female pheromones), and guarding (the fertilized eggs) periods. This study was performed using electron transmission and laser confocal microscopy. Structural changes in the fish olfactory epithelium are associated with the shift in olfactory signals from alimentary to pheromonal. These results expand our knowledge of the odorant-dependent plasticity of the periphery of the fish olfactory system.

Stressed ecological situation in impact zone of the Usolye-Sibirskoe industrial complex caused by long-term inflow of pollutants into the Angara river determines that monitoring surveys of hydrochemical composition of the river are necessary. Comparative assessment of the wastewater and the river water exchange during periods with different anthropogenic load is relevant for establishing consequences and forecasting anthropogenic activities. Therefore, the aim of research was to study processes of transformation of the river water during its mixing with wastewater, which based on determining both concentrations of elements and forms of elements. Low-mineralized (119.1-125.4 mg/l) Angara river water at the background site in 2010 and 2020 are similar by the concentration of major ions and trace elements. The composition of wastewater with salinity of 2130-16322 mg/l varies significantly during different periods of anthropogenic load. In 2010, river sites below wastewater discharges (1.5 and 5 km) are characterized by increased concentrations of Cl-, Na+, As, and Hg relative to background concentrations. In 2020, the level of Mn, Zn, Cg, and Hg concentrations in river water of the farthest site is higher than background, despite the lower content of pollutants in wastewater. Physic-chemical modeling using the software «Selector» has revealed that wastewater differs from natural water by the forms of elements existence in solution, mainly due to predominance of halogen complexes. Wastewater impact causes modification of ratio of element migration forms in the Angara river water, to a greater extent Cd and Hg. Hydrochemical composition of the Angara river is transformed after inflow of industrial zone wastewater. That is indicated by both total elements concentrations and forms of elements. Anthropogenic load reduction causes improvement of hydrochemical characteristics of the Angara river at the sites of river water and wastewater mixing.

Relevance. The necessity to control the hydrochemical regime of water bodies significantly affected by anthropogenic impacts. Aim. To study the spatial distribution of major ions and trace element concentrations and identify natural and anthropogenic formation factors of the hydrochemical composition of the Vikhoreva river and Ust-Vikhorevsky bay of the Ust-Ilimsk reservoir. Objects. Waters of the Vikhoreva river before and after inflow of wastewater from the Bratsk industrial zone, waters of the Ust-Vikhorevsky bay (Vikhorevskaya and Burdoyskaya parts) of the Ust-Ilimsk reservoir. Methods. Determination of micronutrients concentrations in water was performed by inductive coupled plasma mass spectrometry, mercury – by atomic absorption method. Cations and anions were determined using standard methods accepted in hydrochemical studies, Sorg – by titrimetric method, oxygen – by iodometric method. Results. In the Vihoreva river water after wastewater inflow from the Bratsk industrial zone, significant transformations of its hydrochemical composition were detected. Along the water area of river decrease of O2 concentrations (up to 0.3 mg O2/l) and increase of Сorg (up to 131 mg/l), SO42– (up to 262 mg/l), K+ (up to 10.6 mg/l), Cl– (up to 220 mg/l), Na+ (up to 240 mg/l), Mn (up to 248.5 mg/l), Cr (up to 7.4 mg/l), to a lesser extent Al (up to 224.1 mg/l), Co (up to 0.26 mg/l), Cu (up to 5.4 mg/l), Zn (up to 43.2 mg/l), Cd (up to 0.126 mg/l), Pb (up to 0.40 mg/l), Hg (up to 0.0032 mg/l) are observed. In surface waters of the Ust-Vikhorevsky bay concentrations of most components of the main ionic composition and trace elements decrease, as compared to the Vikhoreva river water. Maximum concentrations of Mn (511.5 mg/l), Fe (1567.2 mg/l), Co (0.80 mg/l), Pb (0.77 mg/l) were detected in bottom waters. The main ionic composition and trace element concentrations in the Vihoreva river water are determined primarily by anthropogenic factor. At the same time, the hydrochemical regime of the river is effected by natural factors. Inflow of both waters of the highly polluted and forming waters of the channel part of the Ust-Ilimsk reservoir impacts the hydrochemistry of the Ust-Vikhorevsky bay.

The Irkutsk Reservoir, belonging to the largest unified freshwater Baikal–Angara system, is an important source of drinking water in the region. Therefore, studies of its hydrochemical characteristics are of prime importance in deciding on the role of anthropogenic activity in water quality. The water samples were collected across the reservoir in 2007, 2012, and 2021 and then were analyzed for major ions and trace elements. The data revealed that the distribution of HCO₃⁻, SO₄²⁻, Cl⁻, Ca²⁺, Mg²⁺, Na⁺ and K⁺ is stable across the reservoir. Trace element concentrations varied from 1.13 to 15.39 µg L⁻¹ for Al, from −1 for Cr, from 0.39 to 23.12 µg L⁻¹ for Mn, from 1.25 to 53.22 µg L⁻¹ for Fe, from 0.005 to 0.100 µg L⁻¹ for Co, from 0.20 to 1.98 µg L⁻¹ for Cu, from −1 for Zn, from 0.25 to 0.48 µg L⁻¹ for As, from 0.004 to 0.127 µg L⁻¹ for Cd, from −1 for Sn, from −1 for Cs, from −1 for Pb, from −1 for Th, and from 0.27 to 0.75 µg L⁻¹ for U. The concentrations of all major ions and trace elements in water were below the drinking water standards. CF values showed considerable and high contamination of samples with Al, Mn, Fe, Co, Cu, Cd, Sn, Pb, and Th. PLI values classified the majority of water samples as water with baseline levels of pollutants, and part of the samples was classified as either polluted or highly polluted.

The relevance of studying the spatial-temporal dynamics in the trace element composition of the water at the Angara River source is associated not only with determining the degree of anthropogenic load on the local area of the water body but also with the use of the water chemical composition of the Angara River source as an integral indicator of the hydrochemical state of the entire Lake Baikal. The current work is based on monthly monitoring studies conducted from March 2021 to February 2022 along the left shore, middle part, and right shore of the Angara River source. In water samples, the concentrations of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sn, Cs, Tl, Pb, Th, and U were measured by inductively coupled plasma mass spectrometry. The results indicated that the concentrations of the trace elements lie within mean + 1SD: Cd in 97% of samples; U in 94% of samples; Tl in 92%; Al, Cr, Co, Ni, Cu, Zn, Sn, Pb, and Cs in over 80%; Fe in 78% of samples; and Mn and Th in over 60% of samples. Such results show a high degree of consistency in the water trace element composition at the source of the Angara River. The major factors responsible for the water hydrochemistry at the Angara River source include the runoff of Lake Baikal, the anthropogenic effect of Listvyanka and Port Baikal settlements, and water transport activity. The concentrations of all trace elements in the water of the Angara River source are substantially below the standards for drinking water. At the same time, the single-factor pollution index revealed water samples with considerable contamination by Fe, Zn, Sn, Al, Cs, Mn, Cu, Tl, Cd, Pb, and Th and very high contamination by Cr, Fe, Co, Cs, Tl, Pb, and Th. The pollution load index has classified most of the water samples as having baseline levels of pollutants. Three samples taken from the left shore, four from the middle part, and seven from the right shore were classified as polluted. This means that the ongoing anthropogenic impact may worsen the water quality and have a negative impact on living organisms. The obtained results make a clear case for strengthening environmental protection measures to minimize the anthropogenic effect on the ecosystems of Lake Baikal and Angara River.