Soil Humus Research Articles

Physical and chemical properties of soils in Kharkiv (Ukraine).

The purpose of this work is to determine the physical and chemical properties of soils in different regions of Kharkiv (Ukraine) and to explore their impact on the sorption of heavy metal ions: Cu2+ and Zn2+. It has been established that the soils of gleyic chernozem and typical heavy black earth by their characteristics belong to highly buffer humified soils. According to the increase in the sorption capacity of the soil, it can be arranged in the following row: haplic arenosol < mollic gleyic fluvisol < gleyic chernozem < typical heavy black earth. The index of saturation with cations for typical heavy black earth is an order of magnitude higher than for the other studied soils. The distribution of mobile forms of copper and zinc in soils is determined by their type. The absorption capacity of the studied soils in relation to Cu2+ and Zn2+ directly correlates with a decrease in the pH of the soil solution, with the content of humus and with an increase in the carbon ratio of humic and fulvic acids. The materials of the research can be used to control the ecological situation in the city.

The Effect of Kerosene Pollution on the Cellulolytic Activity of Albic Retisols and Arenosols (Aridic): A Laboratory Experiment.

The results of a laboratory experiment modeling the effect of kerosene contamination on the cellulolytic activity of microbiocenosis of the Albic Retisol (Kaluga oblast, Russia) and Arenosol (Kyzylorda oblast, Republic of Kazakhstan) humus horizons are described. Cellulolytic activity is assessed according to the rate of weight loss in linen cloth fragments during the incubation for 0–3, 3–7, and 7–13 months. The intensity of cellulolytic activity in the unpolluted Albic Retisol is higher as compared with the Arenosol, which is determined by low acidity and an elevated content of organic matter and nutrients. The soil pollution with kerosene to 10 g/kg causes a reversible change in cellulolytic activity of both Albic Retisol and Arenosol (Aridic). A high load of kerosene (≥25 g/kg) inhibits cellulolytic activity in both soils over 13 months of observation.Supplementary InformationThe online version contains supplementary material available at 10.1134/S1064229322020119.Fig. S1. Cellulolytic activity of soils in a laboratory experiment: (a) initial state of linen tissue (test object) and (b) linen tissue after three months of incubation. Table S1. Properties of soil humus horizons.Table S2. Initial water content in the studied soil samples with due account for the added kerosene.Table S3. Cellulolytic activity in soils grouped according to kerosene load (rate of mass loss, mg/g soil per day.Table S4. Significance of differences between cellulolytic activities of contaminated soil samples relative control samples according to the Mann–Whitney U-test. Table S5. Kerosene content in the studied soil samples at the end of the experiment, % of the initial content.

Maple and hickory leaf litter fungal communities reflect pre-senescent leaf communities.

Fungal communities are known to contribute to the functioning of living plant microbiomes as well as to the decay of dead plant material and affect vital ecosystem services, such as pathogen resistance and nutrient cycling. Yet, factors that drive structure and function of phyllosphere mycobiomes and their fate in leaf litter are often ignored. We sought to determine the factors contributing to the composition of communities in temperate forest substrates, with culture-independent amplicon sequencing of fungal communities of pre-senescent leaf surfaces, internal tissues, leaf litter, underlying humus soil of co-occurring red maple (Acer rubrum) and shagbark hickory (Carya ovata). Paired samples were taken at five sites within a temperate forest in southern Michigan, USA. Fungal communities were differentiable based on substrate, host species, and site, as well as all two-way and three-way interactions of these variables. PERMANOVA analyses and co-occurrence of taxa indicate that soil communities are unique from both phyllosphere and leaf litter communities. Correspondence of endophyte, epiphyte, and litter communities suggests dispersal plays an important role in structuring fungal communities. Future work will be needed to assess how this dispersal changes microbial community functioning in these niches.

PKM PENERAPAN PLTS PADA KAWASAN PERTANIAN HIDROGANIK PADI DI BENGKEL MIMPI KABUPATEN MALANG

Currently, rice farming land is getting narrower because it is pressed for housing. Ways are needed to utilize narrow land to develop a rice farming system, including hydrogenic farming, which is an organic cultivation system by planting rice on humus soil in plastic cups planted in a row of paralon pipes above fish ponds, integrating a hydro system (water circulation) nutritious and organic systems (without chemical fertilizers). This Community Partnership Program aims to deal with the problems experienced by service partners, namely the Self-help Agricultural and Rural Training Center "Bengkel Mimpi" in Malang Regency which carries out hydroganic rice cultivation, namely how to obtain alternative sources of electricity so that financial expenditures for electricity can be increased. So far, only state electricity company can save more/reduce, so that the solution and output target implemented in overcoming these problems is in the form of a solar power plant which is used to drive 12 hydraulic water pumps. The method of service is action research: discussion, design and application of solar power plants. After going through technical calculations, 6 100 wp solar panels were installed, complete with support brackets, 3 100 AH batteries, 1 solar charge controller, 1 3000 WA inverter, 12 water pumps. The advantage of this solar power plant is the design aspect of the solar panel support bracket which is made attractively resembles the shape of a sunflower. The test results have been carried out in sunny conditions this solar power plant produces 2,144 Watt Hours. The output of this Community Partnership Program can be used as a model for alternative sources of electricity in other villages nationally, especially on hydrogenic and hydroponic agricultural lands which are located far from the state electricity network.&#x0D; Keywords: hydrogenic rice, action research, solar power generation

Carbon dioxide emission, nitrogen mineralisation and spinach dry matter yield in a loamy humic soil amended with lime and poultry manure.

While application of lime and poultry manure (PM)increase availability of mineral N inacidic humic soils (> 1.8% organic carbon), these amendments enhance decomposition of soil organic carbon (SOC) increasing carbon dioxide (CO2) emissions. This study investigated the effects of co-application of PM and lime on (i) CO2 emission, (ii) concentration of mineral-N and (iii) spinach dry matter yield and nutrient uptake in a humic soil. Two incubation experiments were set up for 84days to determine (i) CO2 emission and (ii) mineral-N on soils fromthe 0-10- and 10-20-cm depths. The treatments were PM (10 t ha-1), lime (12 t ha-1), PM + lime and unamended control. Same treatments (with inclusion of inorganic fertilisers) were applied to a pot trial using soils (0-10-cm depth) that were pre-incubated for 0, 14 and 35days before planting spinach, and dry matter yield and N uptake were determined. Co-application of PM and lime significantly decreased ammonium-N in soilat both depths but increased nitrate-N and CO2 emission than lime alone. Poultry manure significantly increased ammonium-N and CO2 emission at 0-10-cm depth. For all treatments, cumulative CO2-C was significantly higher at 0-10cm. Dry matter yield for PM + lime and lime + mineral N was higher than when separately applied. Pre-incubation of soils with lime and PM, separately or in combination, increased dry matter yield. These findings imply that application of PM and lime in humic soils increases mineral-N availability and crop productivity, especially when pre-incubated for 35days, whilst the increase in CO2 emission could result in the decrease of SOC.

Environmental assessment of the copper content in the soil cover in the South of the Tyumen Region

The article presents data on the content of copper in the plow horizon of the main types of soils of the Tyumen region used in agricultural production, and determines the relationship of its distribution with the main physical and chemical indicators of soils (humus, pH, macroelements). To analyze the geochemical features of the microelement distribution in the soil cover, field, laboratory, and statistical research methods were used. When summarizing and analyzing the material, we used our own research and materials from the reports of the FGBU GSAS Tyumenskaya on the survey of arable soils in the Tyumen region. In all studied types of soils in the south of the Tyumen region, excess of the permissible concentrations of copper is not observed. The content of mobile forms of copper, depending on the type and subtype of soils, varies in the range from 0.15 to 0.25 mg/kg, the total content ranges from 10 to 18 mg/kg. The ratio of the mobile form to the gross content is from 1.05 to 2.29%. A reliable relationship between mobile copper and its total content has not been established. A close correlation has been established between the total content of copper and mobile forms of potassium, humus and the pH level. For mobile forms of copper, there is an average correlation with the content of humus in soils. The relationship between the mobile forms of copper and phosphorus has not been established. The data obtained can be used in environmental monitoring as initial, background reporting points in assessing the degree of pollution of agrocenoses, as well as in predicting the effect of copper in the soil-plant system in the south of the Tyumen region.

Biosorption Potentials of Pleurotus tuber-regium (Fr.) Sing in Lead and Cadmium Polluted Soil

Background/Aim: The heavy metals, cadmium (Cd) and lead (Pb), are often implicated as environmental pollutants. Therefore, the biosorption potential of Pleurotus tuber-regium in lead and cadmium polluted soil was investigated by this work. Methods: Four kilograms of each humus soil sample was weighed into eight different black nursery cellophane bags and polluted with 0.5 g, 1.0 g and 2.0 g of lead and cadmium in triplicate. Pleurotus sclerotia were then planted in these polluted soil samples, and distilled water was added ad libitum. Results: The results showed that the growth performance was dose-related in lead-polluted soil. The Pleurotus tuber regium mushroom in the lead-polluted soil samples indicated a dose-dependent absorbed lead concentration in the results. Cadmium-polluted soil samples did not support the growth of the Pleurotus tuber regium mushroom at the various concentrations of cadmium used after day 30. Therefore, the findings suggest that the Pleurotus tuber regium mushroom and its sclerotia have intrinsic properties for the absorption of lead and cadmium. Conclusion: The findings suggest that the Pleurotus tuber regium mushroom and its sclerotia have intrinsic properties for the absorption of lead and cadmium.

Fungal Perspective of Pine and Oak Colonization in Mediterranean Degraded Ecosystems

Forest restoration has become one of the most important challenges for restoration ecology in the recent years. In this regard, soil fungi are fundamental drivers of forest ecosystem processes, with significant implications for plant growth and survival. However, the post-disturbance recovery of belowground communities has been rarely assessed, especially in highly degraded systems such as mines. Our aim was to compare forests and mined systems for biomass and structure of fungal communities in soil during early stages of tree establishment after disturbance. We performed ergosterol analysis and PacBio and Illumina sequencing of internal transcribed spacer 2 amplicons across soil layers in P. sylvestris, Q. robur and Q. ilex (holm oak) forests and naturally revegetated mined sites. In pine forests, total fungal biomass was significantly higher in litter and humus compared to mineral layers, with dominance of the mycorrhizal genera Tomentella, Inocybe and Tricholoma. Conversely, in oak forests the most abundant mycorrhizal genera were Tomentella, Cortinarius and Sebacina, but the biomass of saprotrophic fungi was greater in the litter layer compared to mycorrhizal fungi, with the genus Preussia being the most abundant. In the revegetated mined sites, ectomycorrhizal fungi dominated in the humus and mineral layers, with the mycorrhizal genus Oidiodendron being dominant. In contrast, in holm oak forests saprotrophic fungi dominated both soil humus and mineral layers, with the genera of Alternaria, Bovista and Mycena dominating the soil humus forest layer, while the genus Cadophora dominated the mineral layer. The habitat-specific differences in soil fungal community composition and putative functions suggest that an understanding of soil–plant–microbial interactions for different tree species and use of specific soil/litter inoculum upon planting/seeding might help to increase the effectiveness of tree restoration strategies in Mediterranean degraded sites.

МЕТОДИЧЕСКИЕ ПОДХОДЫ К ОЦЕНКЕ ЭКОЛОГИЧЕСКОГО СОСТОЯНИЯ ПОЧВ

The article substantiates the methodological approaches used to assess the ecological state of one of the most vulnerable natural objects under intensive economic activity - the soil, which is constantly under physical and chemical (technogenic) loads and unbalanced farming systems. An analysis of the state of the problem showed that a few decades ago, the average content of humus in soils was 4,2%, today it is only 3,2%. The main reasons for the loss of humus are its mineralization, the lack of organic matter entering the soil, and water and wind erosion. The physical and mechanical properties of the soil significantly worsened, and with them the water-air and thermal properties worsened too. Based on the fact that the main task of modern agriculture is to increase soil fertility, thanks to the introduction of energy and resource-saving technologies, it is shown that the main component of the methodological basis for assessing the ecological state of the soil is a system of control indicators, the choice of which is due to the need to adequately characterize the main functions of the soil, soil-forming or soil-destroying processes. The basic requirements for indicators of soil biological activity are formulated. Accoding to the results of studies based on the analysis of methods for assessing the ecological state of soils, agroecological monitoring, which involves the study and generalization of statistical materials for the conditions of the Kabardino-Balkarian Republic, it has been established that promising directions for assessing the ecological state of soils are: taking into account the influence of pollution of various nature on it; combination in the ways of different methods; application of functional-ecological approach; adaptation of methods to certain soil and climatic conditions of territories and specific types of soil; development of methods that have an environmental and economic effect.

YIELD AND BALANCE OF NUTRITIONAL ELEMENTS IN WINTER GRAIN CROPS DEPENDING ON SOWING PERIOD IN THE SOUTHERN STEPPE OF UKRAINE

One of the factors of soil formation is the plant world, which accumulates organic matter through the process of photosynthesis. Organic matter is transformed into humus, which is the main dominant of the soil. In addition to humus, organic matter provides the accumulation of macronutrients such as nitrogen, phosphorus and potassium. The first priority is to create the optimal content of essential nutrients and humus in soils, along with the development of methods to improve the efficiency of fertilizer application. Organic production should not be primitive or extensive. On the contrary, crop production must be sustainable and highly productive. Soil fertility must be restored. The dominant soil is humus. Its quantity is the first criterion for the formation of crop yields, including cereals. Humus is restored at the expense of organic matter through a complex transformation. The aim of the research was to establish the change in soil fertility and the yield of winter wheat and winter barley, depending on the timing of sowing in the conditions of organic farming in the Southern Steppe of Ukraine. Research methods. Field experiments were carried out on the territory of the Odessa State Agricultural Experimental Station of the National Academy of Agrarian Sciences of Ukraine. The experiment studied the effect of sowing dates on the productivity of winter wheat and barley varieties, as well as the renewal of soil fertility and the balance of basic plant nutrients. The total area of the experiment is 4617 m2; the accounting plot is 16.5 m2. Varieties of winter wheat and barley were sown in 10 days interval - from September 25 to October 25. The predecessor is fallow. Placement of variants and repetitions – by the method of the Latin rectangle. Sowing was carried out with a selective planter "Klen – 1.5 C". Repetition – three times. Harvesting was carried out in an inseparable way using the "Sampo – 500" combine. A high yield has a positive effect on the supply of fresh organic matter, that is, there is not only a direct relationship between fertility and yield, but also an inverse relationship: a high yield through plant residues affects soil fertility. As you can see, the larger the yield, the more by-products are formed and the more plant mass accumulates. Winter barley compared with winter wheat has almost the same humus balance. Findings. According to the results of the studies, the best sowing time for all criteria that ensure the formation of grain crop yields and expanded reproduction of soil fertility – Southern chernozem, in terms of humus, nitrogen and potassium content, as well as simple reproduction of phosphorus content, is the second sowing date (October 5).

Uticaj načina korišćenja na strukturu pseudogleja južne Mačve i Pocerine, Srbija

The impact of various types of uses of Pseudogley soils in southern Mačva and Pocerina on the iraggregate distribution and stability was studied on soil samples collected from profiles under forest, meadow and arable land, at three localities. The aggregate composition and stability were determined by Savinov'smethod. The soil structure was assessed by using Revut's coefficient of soil structure (Ks) and Vershinin's coefficient of soil aggregate structure (K A). The results show that the studied Pseudogley soils are characterized by an unfavorable structure, while the type of land use has a significant impact on the aggregate composition and stability, especially in surface Ah and Ahp horizons, where these differences are the most pronounced. The most favorable aggregate composition and highest wet-stability are found in Pseudogley profiles under forest vegetation. The aggregate distribution of meadow profiles was intermediate and of arable land the poorest. Statistical analysis of the collected data shows that Ks values, determined by dry sieving, were the highest in forest profiles (2.261.21 on average), while the values for meadow were 1.591.09 and of arable land 1.140.62. The values of K A , used to assess the aggregate stability to water, also show that forest Pseudogleys have the highest average values (2.051.03), followed by meadow (1.96 0.99) and cultivated soils (1.931.22). The results of correlation analysis indicate that Ks is negatively correlated with clay, pH value and base saturation, but positively correlated with soil humus (r=-0.77,-0.70,-0.81 and 0.79, respectively, p&lt;0.01). Conversely, K A is negatively correlated with humus and positively correlated with clay, pH value and base saturation (r=-0.21, 0.82, 0.69 and 0.69, respectively, p&lt;0.01).

Land use and site effects on the distribution of carbon in some humic soil profiles of KwaZulu-Natal, South Africa

Land use effects on the stocks of soil organic carbon (SOC) are generally based on the topsoil. Although subsoil horizons have lower concentrations, they contain a significant amount of SOC which may be more strongly protected than that in the topsoil layers. Analysis of SOC storage must therefore include the whole profile in respect of climate change mitigation. Humic soils in South Africa have high organic C in the A horizon, while the amount of C stocks through the whole profile depth is unknown. This study was conducted at six sites in KwaZulu-Natal Province to determine the effect of land use and site factors on C stocks, texture, pH and extractable aluminium (Al) and iron (Fe) concentrations and their vertical distribution to 100 cm in soils with thick (>45 cm) and thin (<45 cm) humic A horizons. The land use at some sites had been changed from grassland to maize and cultivated pasture and at others from forest to sugarcane farming. Cultivation with field crops reduced the organic C, mainly in the upper 20 cm (from 110 to 22 g C kg−1), with limited effect in deeper layers. The soils with thick humic A horizons and coarser texture stored more C in the deeper layers compared to those with thin humic A horizons and finer texture which had more of the C stocks in the 0–20 cm depth. Although cultivation reduced the soil C stocks in the surface layers, land use did not significantly affect the overall C stock (0–100 cm) at all sites. The high contents of extractable Fe (up to 340 mg kg−1) and Al (up to 3700 mg kg−1) stabilised the soil C and were more important than the effects of either land use or other site factors.

Humus of the brown soils of the mountain pastures of Uzbekistan

The aim of the study: assessment of humus content and its distribution in the profile of brown soils of mountain pastures in Uzbekistan. Location and time of the study. Soil pits were cut in the Republic of Uzbekistan in seven agricultural regions, widely used in agriculture: Tashkent region, Bustonlik district; Jizzakh region, Zomin district; Samarkand region, Nurabad district; Navoi region, Nurata district; Kashkadarya region, Kitab district; Surkhandarya region, Sherabad district; Namangan region, Papal district. The study was carried out in 2019-2021. Methods. Field studies, sampling and sample preparation were carried out in accordance with the generally accepted methods: soil organic carbon content was measured by bichromate digestion, carbonate content was determined by acidimetric method and soil inorganic carbon content was calculated by subtracting from the total content of carbonates. Silty fractions were isolated by centrifugation. Humus differentiation into reserves and their estimation was carried out according to the method proposed by one of the authors. Main results. The studied brown soils of mountain pastures of Uzbekistan are characterized by loamy granulometric composition, with a clay fraction not exceeding 20%. The content of carbonates is low (2.5–9%), with the maximum amount in the carbonate horizon. Soils are slightly leached. The total humus content in the upper horizon varies from 1% to 6.6%. The dependence of soil humus content on the slope exposure was noted: the soils of the more humid northern and western slopes contain more humus than the southern and eastern ones. In addition, the humus content is significantly affected by erosion. To assess the nature of changes in the organic matter of the brown soils during their agricultural use, humus of the near, labile and potential reserves (as percentage of the total content) was isolated for the first time. It was revealed that humus of potential reserve prevails in soils (35.5-90%). Its vertical distribution is characterized by a sharp decrease in the sub-humus part, while the humus of the near and labile reserves is distributed evenly in the profile, without a pronounced dependence on external conditions and the degree of disturbance. The proportion of insoluble organic substances in the total humus content ranged from 0.39 to 86%, of sparingly soluble organic substances - from 3 to 100%. There is a relationship between the amount of sparingly soluble and insoluble organic matter in the upper horizon and the degree of soil erosion. Conclusion. The distribution of humus and its reserves in the brown soils of the mountain pastures of Uzbekistan is uneven and strongly affected by erosion. The loss of near and labile humus reserves leads to a decrease in the content of total humus. Further study of humus features, humus accumulation and restoration in brown soils is important for the development of recommendations for the rational use, anti-erosion protection and increasing the productivity of mountain pastures in Uzbekistan.

Динамика структурного состояния и ферментативной активности чернозема обыкновенного карбонатного при применении биологически активных препаратов

The purpose is to study the influence of individual and joint application of humic preparation Lignohumate and microbiological fertilizer Baikal-EM on the structural state and enzymatic activity of ordinary chernozem. Materials and methods. Soil samples were investigated by the method of dry sieving to calculate the structural coefficient, by the method of wet sieving to determine the number of water-stable aggregates; the analysis of the dynamics of soil humus was carried out; the dynamics of catalase and invertase activity has been studied. Results. The dynamics of humus during the study period has a similar picture in all variants, however, the end of the growing season in 2011 demonstrated a statistically significant increase in the amount of humus by 0.25 % when a humic preparation and a concentrate of microorganisms are simultaneously applied into soil, in the same variant in the same period, an increase in catalase activity was noted up to 29 ml О₂/(g · min) compared to 20 ml О₂/(g · min) in the control. The application of microorganisms also revealed a correlation between humus and invertase activity: option 4 showed an increase in this indicator to a statistically significant 18 mg glucose/(g · 24 h) in the absence of a significant difference in dynamics in other options. The structural characteristics of soil showed the greatest response to treatment with Lignohumate and Baikal-EM, their application led to the increase in the structure coefficient up to 2.75 compared to 1.6–1.7 in the control variant and with the application of Lignohumate on the leaf. The content of water-stable aggregates in the control variant and with foliar treatment throughout the entire experiment was in the range of 70–75 %, while soil treatment with preparations led to the increase in water resistance of the structure to 90 %. Conclusions. Chernozem turned out to have response to the Lignohumate, application especially in combination with Baikal-EM, directly into soil, which is associated with the stimulation of its own soil microflora by the applied concentrate of microorganisms.

Effects of returning varying amounts of vegetable waste to fields and combined application of decomposing agents on soil humus composition

Effects of returning varying amounts of vegetable waste to fields and combined application of decomposing agents on soil humus composition

Современное использование земель бассейна реки Оса (Верхнее Приангарье)

The territory of the Osa river basin was studied, where under the steppe and forest-steppe vegetation types of soils are common that are not typical for the taiga zone: real chernozems with a relatively thick humus layer, sometimes reaching 45-50 cm, dark humus soils and other types of fertile soils. It has been established that hydrometamorphosed chernozems with a thickness of the humus horizon of more than 1 m are widespread in low relief areas, under conditions of increased moisture. a series of expeditions was carried out to study the soils of natural, arable and fallow lands, as well as pastures. The content of humus and the granulometric composition of soils were determined (types of natural soils: gray typical, hydrometamorphosed chernozem, thin chernozem, typical dark humus; types of agrogenic analogues of natural soils: typical agroabrazem, dark agrozem, typical agrogrey, agroserohumus typical, agrodark humus typical, hydrometamorphosed agrochernozem, typical agrochernozem; more than 30 samples). The influence of these indicators on soil fertility is considered. The change in the nature of land use in the period from 1983 to 2013 has been studied, and possible reasons for these changes. A map of modern land use in 2021 was made. A comparison was made of the nature of modern land use with their use in 1983, 1997, 2005, 2013.

Современное использование земель бассейна реки Оса (Верхнее Приангарье)

The territory of the Osa river basin was studied, where under the steppe and forest-steppe vegetation types of soils are common that are not typical for the taiga zone: real chernozems with a relatively thick humus layer, sometimes reaching 45-50 cm, dark humus soils and other types of fertile soils. It has been established that hydrometamorphosed chernozems with a thickness of the humus horizon of more than 1 m are widespread in low relief areas, under conditions of increased moisture. a series of expeditions was carried out to study the soils of natural, arable and fallow lands, as well as pastures. The content of humus and the granulometric composition of soils were determined (types of natural soils: gray typical, hydrometamorphosed chernozem, thin chernozem, typical dark humus; types of agrogenic analogues of natural soils: typical agroabrazem, dark agrozem, typical agrogrey, agroserohumus typical, agrodark humus typical, hydrometamorphosed agrochernozem, typical agrochernozem; more than 30 samples). The influence of these indicators on soil fertility is considered. The change in the nature of land use in the period from 1983 to 2013 has been studied, and possible reasons for these changes. A map of modern land use in 2021 was made. A comparison was made of the nature of modern land use with their use in 1983, 1997, 2005, 2013.

Soil technogenic radioactivity in the vicinity of the Morzhovets Lighthouse (the Morzhovets Island, Archangelsk region)

The aim of the study was to assess soil technogenic radioactivity in the vicinity of the Morzhovets Lighthouse and surrounding areas by measuring radio caesium (137Cs) specific activity. Location and time of the study. Field work was performed in the area around the Morzhovets Lighthouse (the Morzhovets Island, Archangelsk region) in summer 2022. Methods. Soil samples were collected at 26 sites from the 0-5 cm layer, of which at 12 sites soil samples were collected also from 5-10 и 10-20 cm layers. Aboveground phytomass was sampled as well. In the laboratory the soil samples were air-dried and placed in the Marinelli vessel for measuring 137Cs specific activity by gamma-spectrometry. Registration of the gamma-radiation from the measured soil sample, as well as processing of the obtained spectra were performed using the Progress-gamma software and hardware complex FVKM.412131.002-03. The energy calibration of the gamma spectrometer to control the safety of the setup parameters was carried out after each measurement using a combined control source OISN-137-1 in a Marinelli vessel. The minimal exposure time of the study sample was 3600 sec; however, the time was increased for some samples with low activity. Results. The territory of the Morzhovets Island is occupied by the lowland seaside terraced plane landscapes with tundra vegetation on the peaty podsolised illuvial humus soils, alternating with mires. Caesium specific radioactivity in the top 0-5 cm soil layer, represented by poorly decomposed peat horizon, was found to vary from 9.4 to 144.5 Bq/kg in the peaty illuvial-humus podzol (Gleyic Histic Entic Podzol) and from 12.2 to 139.4 Bq/kg in the bog peat gley soils (Fibric Histosols (Gleyic)). The radio caesium specific activity was shown to decrease sharply with soil depth, reaching the 3 Bq/kg detection limit of the gamma-spectrometer. Comparative analysis of the data showed that in the West Arctic sector 137Cs specific activity decreases from the east to the west, with increasing distance from the Novaya Zemlya, from 80.2 Bq/kg (the Novaya Zemlya Archipelago) and 80.7 Bq/kg (Bolshezemelskaya Tundra) to 19. 2 Bq/kg (the Svalbard Island). Conclusions. The 137Cs distribution in soil of the Morzhovets Island showed the persistent fixation of the element by the upper 5 cm-thick organic part of the soil profile, representing the primary biogeochemical barrier. The vegetation does not accumulate technogenic radioactivity. Overall, the 137Cs distribution in soils around the Morzhovsky Lighthouse displays a medley pattern. The maximal 137Cs specific activity values were measured both in the peaty illuvial-humus podzol and bog peat gley soils.

Mineral-associated soil organic matter: characteristics and behavior under diagenesis

The main part of soil organic matter (OM) is mineral-associated: 88 ± 11% of С and even more – 93 ± 9% of N. The aims of the given study were: 1 – to demonstrate experimentally the adsorption selectivity of organic compounds towards minerals with different physico-chemical properties (palygorskite vs montmorillonite); 2 – to characterize mineral-associated OM of buried Late Holocene palaeosols and estimate its diagenetic transformations; 3 – to investigate the OM of humin from modern soils of different genesis and Pleistocene and Holocene palaeosols and estimate its diagenetic transformations. The basic soil properties were determined using standard methods. Clay fractions (&lt;2 um) – natural organo-mineral complexes (OMC) were obtained by sedimentation, their mineralogy was studied by XRD. The elemental composition of OM was studied with CNS-analyzer. The structural characteristics of organic matter were determined with the solid-state 13C-NMR-spectroscopy and FTIR-spectroscopy, isotopic composition of C and N – by mass-spectrometry. The obtained results show that the characteristics of mineral-associated OM depends on the properties of mineral “filter” as well as the fate of OM under diagenesis: how long, in what quantity and quality it will persist. It was shown that palygorskite adsorbed predominantly O-alkyls, which are chemically strongly bound. As a result, the age of fulvic type humus in palygoskite palaeosols can reach 300 My. From other side humus of smectitic paleosols of the same age is present by deeply transformed aromatic structures (“coal”). Mineral-associated OM of buried under kurgans Holocene palaeosols contains more alkyls and carboxylic groups, is less aromatic in a comparison with OM of the respective soils. The specific feature of mineral-associated OM is its enrichment in N-compounds. The later are present by both vegetal and microbial compounds, and demonstrate the large affinity towards the mineral surfaces. The formation of chemical bounds between them provides the persistence of OM in OMC. E.g. H2O2 treatment results in preferential destruction of C-rich compounds and oxidized OM demonstrates larger C/N values. Mineral-associated OM of buried Holocene soils keeps the decreased values of C/N (7–14 vs 14–21 for OM of whole soils). Additionally they are characterized by heavier isotopic composition of δ15N in a comparison with the respective soils (5–11‰ vs 6–9‰). It could be explained either by the accumulation of microbial N, or increasing of the humification degree – the loss of aliphatic C and increasing of aromaticity. Humin is the considerable part of soil humus. Experimentally shown that OM of humins both of soils and OMC is enriched in O-alkyls and C of acetal groups. OM of humins are not homogeneous, and consists from at least two groups: mineral-associated OM and partly mineralized plant fragments. As a consequence, the content of humin in OMC is smaller in a comparison with respective soils. It is concluded that mineral-associated OM and humin as well as soil humus represent dynamic soil systems.

Complementary ESI and APPI high resolution mass spectrometry unravel the molecular complexity of a soil humeome

High resolution mass spectrometry (HRMS) can resolve thousands of compounds in complex mixtures such as natural organic matter. However, HRMS is seldom sufficient to fully resolve the molecular heterogeneity of Humus in the soil matrix, especially if no preliminary simplification of Humus complexity is applied and if a single ionization technique is used. Here we show that HRMS, when applied with both photoionization (APPI) and electrospray ionization (ESI) and combined with the extensive molecular simplification provided by a humeomic fractionation, significantly increases identification of the molecular composition of soil Humus. Different sequential extractions separate the soil Humeome in three organosoluble fractions (ORG1-3) and two hydrosoluble fractions (AQU2 and RESOM), which showed distinct molecular characteristics. The ORG fractions were particularly homogeneous and rich in alkyl compounds including unsaturated hydrocarbons and lipid compounds found mainly in ORG 1 and ORG 3, but also aromatic compounds comprising lignin-like molecules and condensed structures mainly detected in ORG2. The AQU2 fractions revealed greater complexity and heterogeneity due to the simultaneous detection of sugars, amino sugars, tannins and N-containing compounds not detectable in appreciable concentrations in other fractions. The most recalcitrant RESOM fraction contained highly reduced molecules and condensed structures. The combined use of APPI and ESI showed a marked selectivity in the detection of chemically different molecules separated in each fraction, thereby enhancing their molecular characterization. Specifically, APPI tended to ionize less oxidized and N-containing molecules, and compounds with high concentrations of unsaturation or aromatics, while ESI was more prone to detect highly oxidized compounds consisting of large O/C ratios. Our findings indicate that the combination of a soil Humeome fractionation with a detailed high resolution characterization of differently ionized molecules in the separated fractions enables a far deeper understanding of the molecular composition of soil Humus and the comprehension of its environmental reactivity.