Articles

The number of soil bacteria is an indicator of the condition and health of soils under chemical contamination. However, the native abundance of soil bacteria in the soils of different climatic zones varies significantly. Depending on the soil-forming factors, the number of bacteria in the soils of different climatic zones will vary. To assess changes in the number of soil bacteria, soil contamination of different climatic zones (semi-deserts, steppes and forests) with lead (Pb) in the following concentrations was modeled: 100, 1000 and 10,000 mg Pb×kg^–1 of soil. It was found that at a maximum concentration of 10,000 mg Pb×kg^–1 of soil, the number of soil bacteria in different types of soils was inhibited by 46–92% compared with the control. With an increase in Pb concentration, the number of soil bacteria decreased in semi-desert soils: from 1.61 billion×g^–1 (typical salt marsh) to 0.89 billion×g (chestnut and brown semi-desert soils); in steppe soils: from 4.50 billion×g^–1 (podzolic chernozem) to 0.80 billion×g^–1 (common chernozem); in forest soils: from 8.00 billion×g^–1 (dark gray forest soil) to 1.90 billion×g^–1 (sod-podzolic soil). The soils of the forest climate zone were found to be the most resistant to Pb pollution, while the soils of the steppe climate zone were the least resistant. Among semi—desert soils, the most sensitive are typical salt marshes, among steppe soils — podzolic chernozems, forest soils - sod-podzolic illuvial-ferruginous soils. A comparison of the number of soil bacteria in three climatic zones of Russia with lead contamination has been carried out. The results of the study can be used to indicate the ecological status and health of soils contaminated with heavy metals.

The concept of "soil health" has gained significant popularity in scientific literature as a key framework for ensuring ecosystem sustainability. However, the meaning of this term remains ambiguous, and universal assessment criteria are lacking. The aim of this article is to analyze contemporary definitions of "soil health" proposed by domestic and international soil scientists and to review methods for its evaluation. Emphasis is placed on indicators and monitoring systems that claim a degree of universality in diagnosing soil health. According to the European conceptual framework, the term "soil health" should reflect the broad influence of soil cover on ecosystems, including traditionally recognized aspects such as crop productivity, water and air quality regulation, climate regulation, biodiversity conservation, and the provision of social and cultural ecosystem services. In 2021, the European Union adopted a soil development strategy aimed at achieving healthy conditions for all EU soils by 2050. The term "soil health" is expected to be formalized with the adoption of the Soil Monitoring and Resilience Law, which will establish soil health standards. Researchers from Cornell University (USA) have proposed a similar methodology for comprehensive soil health assessment, termed CASH (Comprehensive Assessment of Soil Health). Both systems – CASH and the Soil Monitoring and Resilience Law – are examined in detail in the article. Additionally, the search for a universal soil health indicator continues; the article discusses metrics such as organic matter content, the soil organic carbon-to-clay ratio (SOC:Clay), and its alternatives (Observed/Typical SOC ratio, SOC/SOCexp). A literature review reveals that the rationale for introducing the term "soil health" remains questionable. In practice, "soil health" is almost universally interpreted as a combination of physical and chemical properties that potentially influence soil fertility. Moreover, practices aimed at restoring "soil health" primarily focus on maintaining agronomic soil properties. In this regard, the indicators and methods for assessing "soil health" differ little from those used to evaluate "soil quality". Russian studies tend to explore fundamental aspects of soil system resilience, emphasizing the biological origins and biodynamic essence of soil. Proposed assessment methods are also based on microbiological indicators: thermodynamic characterization of microbial systems, the heterotrophic parameter of soil health, the self-sufficiency parameter for biophilic elements, phytosanitary soil status indicators, and enzymatic activity. The reviewed indicators and monitoring systems demonstrate potential for comprehensive soil diagnostics. However, their universality is limited by variability in soil-climatic conditions and land-use types.

The review provides a brief description of ecotoxicodynamics as a section of environmental toxicology including the subject of research, theoretical underpinnings and relevant studies. It has been shown that the development of ecotoxicodynamic studies at the present stage associated with the assessment of environmental quality and risk, establishing a database for ecological regulation, analysis of the processes of degradation and self-restoration of natural ecosystems.Particular attention is paid to the analysis of achieved successes in the study of the action of ecotoxicants on the example of their new types (nanoparticles, microplastics, harmaceuticals, food additives). The potential for them to exhibit toxic effects from genetic to ecosystem level including with real existing content has been demonstrated. The effects in organisms manifest as geno- and cytotoxicity and are reflected in violations of the reproductive, immune, enzymatic and digestive systems, behavioral reactions, decrease the rate of growth and development of organisms, the rate of photosynthesis, etc. In ecosystems the consequences of these effects may be а decline in the number and extinction of sensitive species, negative changes in interspecies relationships, loss of biodiversity and productivity of the biocenosis. Gaps in the study of new ecotoxicants are shown, to eliminate them promising research directions have been proposed in particular: investigations оn sublethal effects under real ecosystem loads, assessment of the possibility of developing chronic and delayed effects, detection of the influence of ecotoxicant properties and environmental factors оn toxic effects as well as consideration of combined effects of several ecotoxicants and products of their transformation. The problematic aspects in the study of ecotoxicants were noted by authors of the reviewed research papers. They are (1) the differences in the "scenario" of experiments among different authors, that make comparative assessment difficult to identify general patterns of possible ecotoxicant action in the environment, (2) application model experiments with standard media, that do not reflect real natural conditions and reduce the practical significance of the results obtained.