International conference «Soil as interlink for functioning of natural and anthropogenically transformed ecosystems» devoted to the 90th anniversary of the department of pedology and land resources estimation, Irkutsk State University and year of Baikal

From August 23 to August 29, 2021, Irkutsk hosted the Vth International Scientific and Practical Conference "Soil as interlink for functioning of natural and anthropogenically transformed ecosystems" (hereinafter – the conference) dedicated to the 90th anniversary of the Department of Soil Science and Land Resources Assessment of the Irkutsk State University (ISU) and the Year of Baikal. The total number of participants of the conference was 130 from 27 regions of Russia and 6 other countries (the Republic of Belarus, Bulgaria, Georgia, Moldova, Lebanon and Lithuania). The article presents a brief review of plenary and sectional reports on the following research topics: 1) theoretical soil science: genesis, evolution, classification problems; 2). multidisciplinary approaches of soil science related to the use of soil science methods in other research areas and scientific and industrial areas; 3) Soil resources and land assessment (fertility, degradation, land reclamation, qualitative and economic assessment, ecology and land protection). A total of 43 presentations were given at the conference: 8 plenary and 35 sectional. The interested reader will find a detailed description of the reports presented in this review, as well as other and other conference materials in the collection "Soil as interlink for functioning of natural and anthropogenically transformed ecosystems" (2021). A brief description of two excursions is given: (1) one excursion to the beautiful scenery at the shore of the Lake Baikal, held on August 23, 2021; (2) and another excursion at the Bratsk Reservoir on August 26-29, 2021. The purpose of the excursions wass to get acquainted with the nature and historical and cultural heritage of the Irkutsk region, Lake Baikal, as well as with soils, soil-forming rocks and natural features of the Southern Angara region. During the excursion tour, landscapes, rock outcrops and soil sections were presented: soils on a bumpy-depression relief; Paleolithic site of ancient man "Malta" with sections near the geoarchaeological objects "Malta-Bridge 3"; alluvial gray-humus soil in the floodplain of the Belaya River; exposure of Lower Cambrian rocks near the village Novomaltinsk; Cheremkhovsky coal mine; dispersed-carbonate gypseous chernozem near the Unga River; Novonukutsky gypsum mine; gray metamorphic soil and micellar-segregational chernozem on the bank of the Bratsk reservoir near the village Balagansk. At the end of the tour, the conference participants held a roundtable discussion about the problems of genesis and classification of the soils of the south of the Near-Angara region. The classification position of all the presented soils was justified within the framework of two classification systems: Classification of soils of Russia (2004) and Classification and diagnostics of soils of the USSR (1977). For scientific and informational support of the excursion, the guide "Southern Pre-Angara region: features of soil formation on rocks of different ages" (2021) was prepared and published. The conference aroused great interest among a wide range of specialists in the field of soil science, agrochemistry and ecology, land resource assessment, landscape studies, etc. The organization of such events promotes exchange of experience and strengthens the cooperation between researchers from leading universities and research centers, advancing the effective development of soil science, research methodology and practice, generalizing the information about soil as a link between the functioning of natural and anthropogenically transformed ecosystems.

Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

This study aimed to identify the factors responsible for the major ion composition of pore water from the bottom sediments of the Bratsk water reservoir, which is part of the largest freshwater Baikal-Angara water system. In the Bratsk reservoir, the overlying water was characterized as HCO3–Ca–Mg type with the mineralization ranging between 101.2 and 127.7 mg L−1 and pore water was characterized as HCO3–SO4–Ca, SO4–Cl–Ca–Mg and mixed water types, which had mineralization varying from 165.9 to 4608.1 mg L−1. The ionic composition of pore waters varied both along the sediment depth profile and across the water area. In pore water, the difference between the highest and lowest values was remarkably large: 5.1 times for K+, 13 times for Mg2+, 16 times for HCO3−, 20 times for Ca2+, 23 times for Na+, 80 times for SO42−, 105 times for Cl−. Such variability at different sites of the reservoir was due to the interrelation between major ion concentrations in the pore water and environmental parameters. The major factor responsible for pore water chemistry was the dissolution of sediment-forming material coming from various geochemical provinces. In the south part of the reservoir, Cl−, Na+ and SO42− concentrations may significantly increase in pore water due to the effect of subaqueous flow of highly mineralized groundwater.

Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

This study was aimed at identifying the processes responsible for the major ion composition of pore water from the bottom sediments of the Bratsk water reservoir, which is a part of the largest freshwater Baikal-Angara water system. The pore water ionic composition varies both along the sediment depth profile and across the water area. In pore water, the difference between the highest and lowest values is remarkably large: 5.1 times for K+, 13 times for Mg2+, 16 times for HCO3-, 20 times for Ca2+, 23 times for Na+, 80 times for SO42-, 105 times for Cl-. Such a variability suggests that the dominant factors, influencing pore water chemistry, depend on the location. At the first stages of the sedimentation process, the chemistry of the pore water in the Bratsk reservoir is dependent on HCO3-Ca of the overlying water. Later on, due to the interaction with the sedimentary terrigenous material, they changed to SO4, SO4-HCO3, HCO3-SO4, HCO3-Cl-SO4-water types with exchangeable cations, mainly Ca. Some of pore waters may have a complex genesis associated with subaqueous groundwater discharge. The change in the redox potential observed in the pore water is the indicator of early-diagenetic transformations taking place in bottom sediments.

Analysis of floodable areas of the Angara river

In this work, the authors present a technology for riverside terrain model building that has been tested on a number of scientific projects to study the littoral area of tail race of the Irkutsk Hydroelectric Power Station and the Bratsk Reservoir. This model is used for forecasting changes in the reservoir shorelines associated with wastewater in the cascade of hydroelectric power stations. The technology described in the work was approved to solve a number of practical problems and showed its effectiveness. Specialized application software was developed and terrain data from various sources were used to specify and detail the end result.