Svetlana Alexandrovna Kulachkova

The regularities of methane and carbon dioxide emission from soils and the factors that determine them were investigated in the settlement of Kommunarka (New Moscow) on the building sites of 1938-2014 years and in the recreational zone. It has been shown that the intensity of the formation and oxidation of methane and, as a consequence, the content of this gas in soils and emissions into the atmosphere depend on the time of creation of Urbic Technosols (Folinovic) and the age of other urban soils. In the summer period, the emission of methane from the soils of the residential zone was absent according to median values ​​or did not exceed 0.01 mg CH4·m-2·h-1. Methane was absorbed from the atmosphere. However, local CH4 emission from some soils was observed. During the period with sufficient moisture, maximum emission from the youngest Urbic Technosols (Folinovic) reached 5.25 mg CH4·m-2·h-1 and decreased by an order of magnitude from soils near houses built in 2001 and older. During the dry period, the local emission from young Urbic Technosols (Folinovic) was only 0.03 mg CH4·m-2·h-1 and decreased by three times near houses built in 1938. The most dangerous source of methane to the atmosphere was waterlogged urban soils containing household waste. The maximum CH4 emission from them was 57.15 mg CH4·m-2·h-1. The content of carbon dioxide in the technogenic horizons of Urbic Technosols (Folinovic) and Urbic Technosol (Someriumbric) decreased with an increase in the building age. The emission of carbon dioxide, to a lesser extent than methane, depended on the time of soil formation. Nevertheless, under conditions of sufficient humidification, the maximum CO2 emission were from young Urbic Technosols (Folinovic) (up to 3606 mg CO2 ·m-2·h-1). Under conditions of insufficient moisture, maximum CO2 emission were from the soils of older microdistricts (up to 664 mg CO2 ·m-2·h-1) and from Folic Gleyic Fluvisol (up to 1901 mg CO2 ·m-2·h-1).

Bioassay is a popular method for the ecotoxicological state assessment of various components of urban ecosystems — soils, water bodies and air. However, little is known about the potential of bioassay application to determine the ecotoxicity of urban dust — a complex heterogeneous media composed of natural and technogenic particles.
Many components of urban dust are known to pose toxic eff ects to living organisms. The aim of this article is to review the existing practices for the ecotoxicological assessment of urban dust and to identify the key trends in the development of the bioassay. The existing studies revealed a high potential of bioassay methods as they are sensitive to a wide range of pollutants present in dust; able to refl ect the dust toxicity selectively depending on environmental factors, and can be implemented using organisms of diff erent trophic levels. The following dust characteristics should be taken into account for the bioassay method proper choice: sample mass, wettability, pH, water-soluble ions and organic matter content. Due to complexity of urban dust composition and diff erent potential for the transition of its components into water extracts, it is recommended to prioritize the bioassay realized on solid dust substrates
instead of extracts. For the comprehensive assessment of dust impact on urban ecosystem, a set of organisms of different
trophic levels should be considered instead of one. Standards should be developed for dust bioassay in order to unify the results obtained by diff erent researches. Th e choice of the control sample is one of the most important
methodological questions.

Th e methodology for biodiagnostics of the ecological state of soils and other environmental objects involves the use
of two approaches: bioindicative observations in situ and biotesting of samples, carried out according to standard methods in controlled laboratory conditions ex situ. An integrated assessment of soils on an interdisciplinary basis in accordance with the international standard ISO19204-2017 makes it possible to diagnose of soils “health” based
on biotic parameters in the course of natural environmental observations, ecotoxicity indicators, which are supplemented
by the results of quantitative chemical analysis (TRIAD methodology). For soils, indicators of the state of higher plants and microbial communities, especially in agroecosystems, are of paramount importance. The article analyzes the advantages and limitations of well-known methods of phytoindication, laboratory phytotesting, soil
respiration, structural and functional indicators of microbiota diversity and bacterial biosensors. Th e responses of living systems to the same pollutant content largely depend on the carbon content of organic matter. The existing regulatory framework for the ecological assessment of the biological state of soil ecosystems practically does not take into account this, as well as the level of mineralization and pH of the analyzed objects. For an adequate assessment of the ecological quality of soils, it is proposed to improve the methods of measuring toxicity by more targeted recommendations for application (for example, for certain gradations of humus content, mineralization, pH).

Due to the need to develop technologies for reducing carbon dioxide emissions and increasing the C-absorption
capacity of natural and anthropogenic ecosystems, the possibility of using mineral fertilizers to regulate microbial
respiration and CO2 emissions from urban lawn soils was evaluated. Th e studies were carried out on the territory of
the Botanical Garden of Moscow State University on the Lenin Hills in a small-plot experiment with the fractional
application of four types of complex fertilizers (NPKS 27:6:6:2, NPKS 21:10:10:2, NPK 15:15:15 and NPK 18:18:18
+ 3 MgO + trace elements (TE)) at doses of 60 and 120 kg N ha-1 during the growing season. Th e carbon content
of microbial biomass (Cmic) using substrate-induced respiration was studied, the basal respiration (BR) of soils was
estimated, and the emission of CO2 from soils using closed static chambers was determined. Тhe Cmic content in the
soil of the control plot in the summer period varied within 1300–1450 μg·g-1. Th e application of NPKS 21:10:10:2
and NPK 18:18:18 + 3 MgO + TE at a low dose increased the Cmic content by 12–35% for two weeks, then it decreased.
Th e application of all fertilizers for a short period increased basal respiration of soils and CO2 emission,
maximum on the 6th day. After two weeks, the increase in the intensity of BR and CO2 emission decreased or it
reached the control values (1,5 μg C-CO2·g-1·h-1 and 500 mg·CO2 ·m-2·h-1 respectively) or less. In the short term,
the lowest intensity of CO2 emission and a surge in basal respiration, along with an increase in microbial biomass,
were observed with the addition of fertilizer NPKS 21:10:10:2. The greatest change in the functioning of the soil
microbial community, revealed by the maximum qCO2, occurred with the introduction of NPKS 27:6:6:2. The dynamics
of CO2 emission from the soils of the small-plot experiment from April to October correlated with the soil
temperature (rS = 0.66, p<0.05, n=135). In all periods of the study, the minimum CO2 emissions were noted for the
plot with NPKS 21:10:10:2 fertilizer.

Microbial production and CO2 emission in Albic Retisol (Loamic) and Albic Retisol (Aric, Loamic) of Lomonosov Moscow State University carbon polygon «Chashnikovo»≫ in the Moscow region were studied during the peak of vegetation activity. The object represents monitoring sites in two natural ecosystems (secondary spruce forest and mixed-grass meadow) and in two agroecosystems (perennial grasses and bare fallow). The soils differed in their stocks
of organic matter carbon (Corg), microbial carbon (Cmic), and potentially mineralizable carbon (Cpm). The highest values of microbial indicators and carbon content were observed in the upper 30 cm with a maximum in the upper 10 cm. Corg stocks in the 0–30 cm layer were 1.1–1.3 times higher in agricultural soils (72.7–75.6 t ha-1) compared to natural ones (59.4–65.0 tha-1). The contribution of Cmic stocks to Corg stocks in meadow soils and agricultural soils under perennial grasses (1.8 and 1.4%) was higher than in forest soils and soils under bare fallow. Сpm stocks in natural soils (1.34 and 0.97 tha-1 for a layer of 0–10 cm) were 1.3–2.3 times greater than in agricultural soils, but the intensity of mineralization of organic matter in agricultural soils was 1.4–2.9 times lower than in soils of natural ecosystems. For ecosystems with similar vegetation, the influence of Сpm stocks on the amount of microbial CO2 production was shown; its proportional increase was noted. Maximum potential microbial CO2 production (4.8 gCm-2day-1 for the 0–10 cm layer and 10.5 gCm-2day-1 for the 0–30 cm layer), Cmic stocks (0.50 tha-1), as well as CO2 emission (11.09±0.29 gCm-2day-1) were characteristic of the soils of a dry meadow. In other ecosystems, CO2 production by microorganisms was lower by approximately 2 times. Since CO2 emission, in addition to microbial respiration, is also caused by the respiration of plant roots, its minimum values were observed in agricultural soils under bare fallow (5.01±1.43 gCm-2・day-1). CO2 emission from forest soils and agricultural soils under perennial grasses was statistically not significantly lower compared to the meadow.