Frost Depth Research Articles

Study on anti-frost heave effect of new thermal insulation subgrade of highway in seasonally frozen soil regions.

Frost heave is one of the important factors affecting the long-term stability and safe operation of subgrade in seasonally frozen soil regions. To investigate the anti-frost heave effect of foam concrete insulation and composite insulation structure subgrade, a multi-physics fields coupling numerical simulation was employed. From the perspective of hydrothermal process of the subgrade, the ground temperature distribution, maximum freezing depth, ice distribution, and maximum frost heave are systematically analyzed. The results indicate that the foamed concrete insulation layer subgrade exhibits a significant anti-frost heave effect. Meanwhile, to alleviate the sunny-shady slopes effect on subgrade in the seasonally frozen soils regions, the composite insulation structure combining XPS insulation board with foamed concrete insulation was recommended. Moreover, the appropriate anti-frost heave measures for subgrade are proposed, which considering the different frost heave characteristics. The findings can serve as a reference for the prevention and control of frost heave in highway subgrade and for the application of foam concrete insulation layers in seasonal frozen soil regions.

Assessment of Frost Depth in Romania

The study of severe climate and weather conditions has accelerated in recent decades, partly due to political engagement. However, historical climate monitoring data has not received sufficient attention. Reliable assessments of the maximum extent of soil freezing are crucial for determining construction costs and building foundations. Structural designers also require reliable local meteorological data. This study presents calculations of these parameters for Cluj Napoca city. For instance, a revised frost depth map for Romania is necessary due to recent climate studies indicating a rise in both regional and global surface temperatures, with the most notable warming for the previous thirty years. The findings from this investigation could help reduce frost-related disasters and inform policies and measures for adapting geotechnical and structural designs in Romania.

Insights into freeze–thaw and infiltration in seasonally frozen soils from field observations

AbstractSnowmelt infiltration into frozen soils in seasonally frozen landscapes is a critically important hydrological process, with consequences for agriculture, water resources, and flooding. The partitioning of snowmelt between infiltration and runoff in any given location and in any given year is highly uncertain. While it is intuitive to expect lower infiltration capacities in frozen soils, extensive past field research has shown that infiltration is often the dominant flux over runoff during this process, and this is attributed to infiltration into air‐filled macropores. Despite this understanding, we still lack models that can predict frozen soil infiltration reliably. In this study, we examine detailed field observations from the seasonally frozen Canadian Prairies to determine the controls on soil freeze/thaw, snowmelt partitioning, and groundwater recharge. We show how soil moisture, water table depth, snow water equivalent, and air temperature are all significant and confounding factors that determine soil freezing depth and snowmelt partitioning.

Model for Predicting the Anti-Frost-Jacking Capacity of a Belled Pile in Seasonally Frozen Soil Regions

In seasonally frozen soil regions, frost heave may result in frost jacking or the failure of piles, posing a potential threat to the structural integrity of upper constructions. The belled pile, which has an enlarged base, can be applied in such places to reduce this adverse effect. To predict the anti-frost-jacking capacity of belled piles, a model is proposed that is based on Mindlin’s solution and the principle of virtual work. The anti-frost-jacking capacity is characterized by the anchorage factor: the ratio between the anchorage force and the tangential frost heave force. Based on this model, we consider factors affecting the anti-frost-jacking capacity, including the tangential frost heave stress, the ratio of enlarged base diameter to pile diameter ( D/ d), the ratio of embedded depth to enlarged base diameter ( L/ D), and the bell angle. The results of the proposed model agree well with test data, thereby validating the model. The anchorage force of a belled pile increases linearly with tangential frost heave stress and exponentially with freezing depth. However, increasing the tangential frost heave stress has no effect on the anti-frost-jacking capacity at the same freezing depth. Moreover, increasing D/ d or the bell angle while decreasing L/ D can benefit the anti-frost-jacking capacity of a belled pile.

Field evaluation of a novel thermally controlled subgrade for mitigating frost heave

ABSTRACT A new type of thermally controlled subgrade is proposed to mitigate persistent frost heave issues of railway subgrades in seasonally frozen regions. A dedicated ground-source heat pump system collects low-grade geothermal energy from the stable soil layer near the subgrade, converts it into high-grade thermal energy, and transfers it to the frigid subgrade for active heating and temperature control, thereby eliminating the adverse effects of frost heave. A 20-metre-long test section of thermally controlled subgrade was constructed in a frost heave section of the Junggar-Shenchi Railway in Shanxi Province, China. During the winter spanning 2021 and 2022, the heating temperature of the heat pump, the thermal regime of the test section subgrade and the natural subgrade, the frost depth, and the track heave were measured. The results indicate that the heat pump temperature could reach a peak of 59.4 °C, with the average daily heating temperature during intermittent operation reaching 25.2 °C or higher, indicating an efficient heat source that plays a favourable role. The freezing period of the natural subgrade lasted for 141 days, while the subgrade in the test section was 20 days shorter. The maximum frost depths at the track centre, shoulder, and embankment slope toe in the test section were 88 cm, 75 cm, and 58 cm, respectively. These depths were 60 cm, 122 cm, and 78 cm less than those of the natural subgrade, effectively controlling the frost depth within the threshold that may cause potential structural damage. Under natural conditions, the track heave reached a peak of 9.4 mm, leading to a harmful frost heave scenario. In contrast, the track deformation in the test section was less than 3 mm, which did not exceed the regular maintenance threshold. The thermally controlled subgrade proves to be an effective method for preventing and controlling persistent frost heave damage in critical locations such as low embankments, cut section subgrades, turnout areas, and culvert roofs.

Seasonal freeze–thaw front dynamics and effects on hydrothermal processes in diverse alpine grasslands on the northeastern Qinghai–Tibet Plateau

The dynamics of the freeze–thaw front strongly affect the transfer and exchange of water and energy in seasonally frozen zones. This study aimed to characterize the variations in the seasonal freeze–thaw fronts of diverse alpine grasslands and their effects on hydrothermal processes in the Qinghai Lake Basin (QLB). Field experiments were carried out on alpine meadow and steppe transition (AMS), alpine steppe (ASP) and Achnatherum splendens steppe (AST) ecosystems in the QLB, with 2 years of continuous high-frequency year-round observations. The results revealed that the seasonal freeze–thaw front was characterized by three distinct stages, in which the durations of slow freezing period (SF) and thawing period (T) were much shorter than that of rapid freezing period (RF). The maximum seasonal freezing depth in 2018–2020 were ranged from AMS (322.65 cm), AST (271.98 cm) and ASP (200.00 cm). The liquid soil volumetric water content (SVWC) decreased in all three ecosystems during the RF period, but increased during the SF and T periods. During the RF period, the SVWC of the AMS, ASP and AST decreased the most by −13.28 %, −9.52 % and −15.29 %, respectively. In the SF period, the SVWC of the AMS, ASP and AST increased the most, by 3.97 %, 9.52 % and 6.33 %, respectively, and by 13.37 %, 12.73 % and 12.44 % in the T period. During the freeze–thaw process, the SVWC and soil temperature mainly exhibit logarithmic and quadratic functions. The changes in the freeze–thaw front and SVWC in AMS were largely consistent, while those in ASP and AST experienced time lags. The freeze–thaw depth and net radiation of the RF, SF and T periods were fitted via the quadratic polynomial method. The freeze–thaw depth and soil heat flux were linearly fitted in the RF and SF periods, and the quadratic polynomial method was used in the T period. The effect of net radiation and soil heat flux accumulation on thawing front were more obvious in AMS than in ASP and AST. These findings are important for improving our understanding of water and heat transfer processes during the freeze–thaw period.

Designing ballastless high-speed railways in frozen regions: A dynamic analysis using three-dimensional numerical modelling

Many high-speed railways (HSRs) have been constructed in the frozen regions of China, with additional lines expected to be developed in the future. However, research into the dynamic response of embankments in these regions under moving train loads has been limited, particularly in view of potentially increased train speeds. Therefore, this study developed an indirect thermal–dynamic coupled three-dimensional finite-element model to investigate the dynamic responses of railway subgrades induced by high-speed trains in frozen regions. The study examined dynamic responses in relation to underlying layer stiffness, frost depth, and train speed. Dynamic amplification factors for train speed and frost depth were derived from statistical analysis of simulation results. A potential method was proposed to predict the long-term track performance of HSRs in frozen regions under conditions of higher train speeds. The study suggests practical recommendations, providing essential guidance to railway engineers in devising optimal strategies for railway design in frozen regions.

A dynamic boundary condition finite difference model for predicting pavement profile temperatures: Development and validation

The appearance of ground frost is of vital importance in construction and maintenance of roads in cold climates. Frost often causes ground heave and subsequent road damage, which must be taken into account in designing the road structure. Frost depth, pavement temperature, and freezing/thawing cycles are also important for estimating the frequency of road maintenance and treatment. Various analytical, numerical, and empirical models have been developed to estimate the surface temperature of the pavement and to model the heat flow in the underlying layers. The pavement surface experiences a variety of intricate nonlinear heat transfer mechanisms during winter, making it challenging to accurately model the surface boundary. Dynamic variation of parameters such as cloud cover and traffic density during the modeling period introduces additional complexity. To address this challenge, we have established an experimental setup in Luleå, Sweden, to measure pavement profile temperatures during the winter season. Additionally, we have developed a Finite Difference Model that utilizes local weather data including dynamic cloud cover, and which also takes traffic into account. The experimental and simulation findings demonstrate how the impact of surface temperature fluctuations diminishes and, more or less, vanishes for depths more than 55 [cm] below the pavement surface. The Finite Difference Model presented in this study exhibits the ability to forecast the pavement profile temperatures, including the surface temperature based on weather conditions, with acceptable precision for at least 3 days. As a consequence, a reasonable assessment of pavement layer conditions appears feasible based on local weather conditions, and the model can serve as a useful tool for planning road maintenance and construction in cold regions.

Моделирование теплового режима дорожной одежды и земляного полотна лесовозных дорог

Soil freezing is observed throughout almost the entire forested area of the Russian Federarion in winter. The effect of negative temperatures on dusty-clay soils causes a number of adverse processes that change the properties of the soils themselves. One of the most unfavorable of these processes is the accumulation of moisture in soils under the influence of the movement of the freezing front. When freezing, water-saturated clay soils increase dramatically in volume. This leads to the appearance of frost heaving in the active zone of the forest roadbed, which has an extremely adverse effect on the structure of the entire pavement and can lead to damage to the pavement with a sharp deterioration in the transport and operational qualities of forest roads. To combat frost heaving, it is necessary to study the patterns of changes in the water-thermal regime of road structures. The depth of freezing of the pavement and the roadbed is of the greatest importance for predicting frost heaving and developing measures to combat this phenomenon. The article describes the developed system for monitoring the temperature of the road structure to a depth of 3 m and the measurement results which allow us to evaluate the temperature change at different depths from the road surface and determine the freezing depth. A total of 32 sensors have been installed with a step of 10 cm. A numerical simulation of the freezing process of the pavement and the upper part of the roadbed of a forest road has been performed, with the results compared with the indicators of field observations. Good data convergence has been revealed. According to the results of experimental studies, the freezing value has been 173 cm, and according to the results of numerical simulation – 190 cm. The average error in the results of numerical simulation of the freezing process of the pavement and the upper zone of the forest roadbed has been 8–10 % compared to the experimental data.

Развитие модели динамики снежного покрова Гидрометцентра России

Conceptual models of runoff formation used in the operational practice of hydrological forecasting by the Hydrometeorological Center of Russia include simplified parameterization of snow cover dynamics based on the use of snow cover melting coefficient, water-retaining capacity of snow and secondary freezing of meltwater in case of return of negative air temperatures. This schematization of the process is well established for the reliable calculation of the snow water equivalent for subsequent use in the calculation of meltwater inflow to the catchment surface and the calculation of streamflow characteristics. At the same time, the lack of calculation of snow density and snow height in the used schematization restricts the use of schemes for calculating of soil freezing depth in hydrological models, which seems to be extremely important for modelling runoff on mid-latitudes rivers, i.e. for the most Russian rivers. To overcome this disadvantage, the snow density and snow height parameterization was added to the calculation scheme of the model, which was verified using Roshydromet’s snow measurement routes data and shown a good and satisfactory quality of modeling of model characteristics.

Investigation on moisture-heat-deformation behaviors of the ordinary railway subgrade in seasonally frozen regions

The stability and service performance of ordinary railway subgrade are often challenged by frost heave distresses in seasonally frozen regions. This paper analysis the moisture-heat process and frost heave characteristics of the subgrade of Qinghai-Tibet Railway (QTR) using on-site monitoring data. The development mechanism of deep frost heave in ordinary railway is discussed, and combined with numerical simulation, the mechanism of significant lateral differential frost heave of ordinary railway subgrade is also revealed. The monitoring results show that the maximum freezing depth of the subgrade is 1.88 m, and the maximum frost heave is 32 mm. The freezing cycle can be divided into four stages by freezing rate and thawing rate: repeated freezing-thawing cycles, rapid freezing stage, slow freezing stage, and bidirectional thawing stage. The freezing rate of 0.53 cm/d and high moisture content of subgrade in the slow freezing stage are the main reasons for the development of deep frost heave in ordinary railway subgrade. The existence of ballast layer is the primary factor that causes the difference of initial freezing time, moisture-heat change and distribution at different positions of ordinary railway subgrade, which ultimately results in the lateral differential frost heave exceeding the allowable value of 15 mm.

Calculation of seasonal soil freezing depth by engineering and numerical methods

Introduction. Provided by severe climatic conditions in the Russian Federation, seasonal soil freezing and emerging cryogenic processes cause frost heaving that negatively affect foundations and buried structures. As the magnitude of frost heaving forces significantly depends on the soil freezing depth, the assessment of soil freezing depth becomes very relevant.Aim. Calculation and estimation of the depth of seasonal soil freezing by engineering and numerical methods.Materials and methods. Calculations of soil freezing depth were performed for two sites composed of sandy loam and loam. Engineering calculations were performed according to four methods set forth in the normative documents, namely Recommendations on Thermal Engineering Calculations and Pipeline Laying in Areas with Deep Seasonal Soil Freezing, Handbook on Construction on Permafrost Soils, Recommendations on Accounting and Prevention of Deformations and Forces of Soil Frost Heaving, Recommendations on Forecasting the Thermal State of Permafrost Soils. Numerical calculations were performed in the Frost 3D and Borey 3D software systems. The experimental sites are located in the Tymovsky district of Sakhalin Oblast, where the Sakhalin-2 pipeline was laid.Results. The engineering methods for calculating the required depth of soil freezing give overestimated results when using a large range of climatic and soil parameters: air temperature, snow cover height and density, wind speed, convective heat transfer coefficients, total solar radiation, surface albedo, maximum elasticity of water vapor, etc. At the same time, the use of Stephan’s formula with a limited set of input parameters gives results close in values. The numerical methods showed close results among themselves, though 32–47 % more than the results of engineering calculations at bare ground surface.Conclusions. Research on the dynamics of soil freezing depth in field conditions is suggested to be carried out and compared with the results of engineering and numerical calculations to improve these methods.

A critical assessment of geological weighing lysimeters: Part 2—Modelling field scale soil moisture storage and hydrological fluxes

AbstractLand surface models (LSMs) are used to simulate the terrestrial component of water, energy, and biogeochemical cycles. These simulations are useful for water resources management, drought and flood prediction, and numerical climate/weather prediction. However, the usefulness of LSMs are dependent by their ability to reproduce states and fluxes realistically. Accurate measurements of water storage are useful to calibrate and validate LSMs outputs. Geological weighing lysimeters (GWLs) are instruments that can provide field‐scale estimates of integrated total water storage within a soil profile. We use field estimates of total water storage and subsurface storage to critically evaluate two different land surface models: the Modélisation Environnementale communautaire—Surface Hydrology (MESH) which uses the Canadian Land Surface Scheme (CLASS), and the Structure for Unifying Multiple Modeling Alternatives: (SUMMA). These models have differences in how the processes and properties of the land surface are represented. We attempted to parameterize each model in an equivalent manner, to minimize model differences. Both models were able to reproduce observations of total water storage and subsurface storage reasonably well. However, there were inconsistencies in the simulated timing of snowmelt; depth of soil freezing; total evapotranspiration; partitioning of evaporation between soil evaporation and evaporation of intercepted water; and soil drainage. No one model emerged as better overall, though each model had specific strengths and weaknesses that we describe. Insights from this study can be used to improve model physics and performance.

Stakeholder perceptions, challenges, and sustainable solutions for achieving safely managed sanitation in Kazakhstan: a case study from a cold region

ABSTRACT In this paper, we present survey results from 30 sanitation stakeholders across the public and private sectors, professional associations, non-governmental organisations (NGOs), and households in the two coldest cities of Kazakhstan. The objectives were to identify the perceived sanitation challenges, document innovative, and traditional solutions employed by the stakeholders to manage sanitation challenges during the cold season, and to propose initiatives and policy interventions to alleviate pressing sanitation issues. Commonly encountered problems included improper installation of septic tanks (e.g. above the frost line) by non-professionals and the difficulty of households to access latrines during heavy snowfall events. Ninety-three percent of respondents expressed that foul odours and sewage overflows were their primary concerns, with only 7% reporting health impacts as a primary concern. There were significant differences in the viewpoints of the respondents regarding the extent of sanitation infrastructure maintenance or upgrades needed in the two cities, suggesting regional differences across the country rather than a uniform national situation. In the context of Kazakhstan, local NGOs were identified as playing a key role in engaging with households to co-devise affordable and sustainable sanitation solutions that are suitable for cold regions, which can then be communicated to other sanitation stakeholders, including the public sector.

Changes in the standard freezing depth of seasonally frozen ground in China over the last 50 years

ABSTRACT In recent years, under the influence of global warming, the freezing depth of seasonally frozen ground (SFG) has decreased at an accelerating rate. This has affected engineering and construction insofar as accurate determinations are needed of SFG areas and the amount of frost heaving. In this study, a method of deriving the E-factor using the improved Stefan formula was used to study changes in the standard freezing depth (SFD) of SFG in China. The method was used to reveal the trends and patterns of changes in the SFD of SFG over the past fifty years. The study relied on ERA5L and reanalysis data and empirical formulas for standard sites in China’s SFG regions. Raster data of the interdecadal SFD in SFG areas of China from 1971 to 2020 were generated to analyze changes in the SFD. Our results show that in the past fifty years, the SFD in China’s SFG areas has shown a downward trend, with the SFD changing at an average rate of −6.749 cm/10a years. The average SFD in the 1970s, 1980s, 1990s, 2000s, and 2010s was 111.31, 107.13, 95.69, 89.84, and 86.21 cm, respectively. From the overall performance of the SFD in different decadal periods, the SFD in central and northeast China changed sharply within the range of 35° N to 50° N in SFG regions. The boundary lines of low-value SFDs expanded sharply to the north as the latitude increased, and the boundary lines of high-value SFDs contracted sharply.

Projected future changes in the cryosphere and hydrology of a mountainous catchment in the upper Heihe River, China

Abstract. Climate warming exacerbates the degradation of the mountain cryosphere, including glacier retreat, permafrost degradation, and snow cover reduction. These changes dramatically alter the local and downstream hydrological regime, posing significant threats to basin-scale water resource management and sustainable development. However, this issue is still not adequately addressed, particularly in mountainous catchments. We developed an integrated cryospheric–hydrologic model, the FLEX-Cryo model, to comprehensively consider glaciers, snow cover, and frozen soil and their dynamic impacts on hydrological processes. Taking the mountainous Hulu catchment located in the upper Heihe River of China as a case study, we utilized the state-of-the-art climate change projection data under two scenarios (SSP2-4.5 and SSP5-8.5) from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) to simulate the future changes in the mountainous cryosphere and their impacts on hydrology. Our findings showed that under the medium-emission scenario (SSP2-4.5) and high-emission scenario (SSP5-8.5), by the end of the 21st century, the glacier will completely melt out around the years 2051 and 2045, respectively. The annual maximum snow water equivalent is projected to decrease by 41.4 % and 46.0 %, while the duration of snow cover will be reduced by approximately 45 and 70 d. The freeze onset of seasonally frozen soil is expected to be delayed by 10 and 22 d, while the thaw onset of permafrost is likely to advance by 19 and 32 d. Moreover, the maximum freeze depth of seasonally frozen soil is projected to decrease by 5.2 and 10.9 cm per decade, and the depth of the active layer will increase by 8.2 and 15.5 cm per decade. Regarding hydrology, catchment total runoff exhibits a decreasing trend, and the tipping point of glacier runoff occurs approximately between 2019 and 2021. Permafrost degradation will likely reduce the duration of low runoff in the early thawing season; the discontinuous baseflow recession gradually transitions into linear recessions, and the baseflow increases. Our results highlight the significant changes expected in the mountainous cryosphere and hydrology in the future. These findings enhance our understanding of cold-region hydrological processes and have the potential to assist local and downstream water resource management in addressing the challenges posed by climate change.

Prediction of thermal regime and frost heave deformations of subgrade soils during non-stationary heat and moisture transfer

In order to ensure the safe operation of high-speed trains in cold regions, frost heave is one of the basic problems in the research for prediction and control roadbed deformation in such regions. In this paper, based on the classical hydrodynamic model we developed a method of studying thermal regime of soils and predicting frost heave deformations of subgrade soils. Our coupling model takes into account the mutual influence of temperature and soil moisture during non-stationary processes of heat and moisture transfer, calculation of frost heave deformation based on calculated result of the temperature and moisture fields of the roadbed. We have also observed the change of the soil temperatures and frost heave deformation in a freezing-thawing cycle at the geodesic center of PGUPS. The field observation results show that the soil temperature variations amplitude decreases with depth. The simulation verification results and the field observation data show good reproducibility, thus the reliability of the model is confirmed. At last, the paper presents the application of the method in improving high speed railway lines (HSRL) subgrade design in order to reduce frost heave deformations. Based on the results of calculations, it is recommended to lay a thermal insulation layer at the depth of 0.2 m below the subgrade and on the slopes to reduce frost depth and frost heave deformations of subgrade soils.

Freezing and thawing characteristics of seasonally frozen ground across China

Observations from 1,047 meteorological stations from September 1, 2006 to August 31, 2015 revealed regional differences in the freezing and thawing processes of seasonally frozen ground (SFG) across China. SFG generally undergoes a one-way freezing process (i.e., top-down), and the stations with a large freeze depth generally experienced long freeze durations. During the thawing process, soil is generally characterized by two-way thawing (i.e., top-down and bottom-up) in the region north of 35′N, especially north of 30′N (except in northeastern China). The onset of thawing from the bottom occurs earlier than that from the top at most stations in the two-way thawing region. The stations exhibiting one-way thawing (i.e., bottom-up) were mainly located on the southern edge of eastern China (east of 110°E) and in southern part of Xinjiang and southeast part of the Qinghai–Tibet Plateau. The freezing process lasts several days to more than four months longer than the soil thawing process, and this difference tends to be larger in high-latitude and high-altitude regions. All of the sites experienced a discontinuous freeze–thaw process, the station-average duration of which was less than a quarter of that of the continuous freeze–thaw process. Strong associations of soil freeze depth with air temperature (as characterized by the air freezing index and air thawing index) implied a dominant influence of air temperature on the soil freeze–thaw process. During the freezing process, this relationship was partially modulated by snow cover in snowy regions, such as northeast China, northwest China, and the eastern Tibetan Plateau. This paper provides the first overview of regional differences in the freezing and thawing processes of SFG over China, and the findings improve our understanding of the soil freeze–thaw process and provide important information to support research into regional landscapes, ecosystems, and hydrological processes.

Influence of snowpack on soil organic carbon decomposition in a northern peatland

Peatlands play a significant role in maintaining the carbon balance and regulating the climate. The turnover of soil organic carbon (SOC) in peatlands is mediated by snowpack, which affects microbial decomposition through its regulation of hydrothermal conditions. However, the impact of snowpack on carbon dynamics in peatlands is not fully understood, particularly in the context of decline in snowpack due to climate warming. To address this issue, an on-site experiment was conducted involving snowpack manipulation (undisturbed and snow removal) to investigate the effects of snowpack on SOC decomposition at depths of 0–30 cm (topsoil) and 30–60 cm (subsoil). Various techniques such as X-ray absorption near-edge structure, synchrotron radiation micro computed tomography technology and microbial metagenomics were utilized to measure SOC content and fractions, pore structure and bacterial community’s structure and function. Results showed that snow removal delayed the start of soil freezing date by 27 days and advanced the start of thawing date by 39 days, increased maximum freezing depth by 27.9 cm and frequency of freeze–thaw cycles, and decreased average temperature of topsoil and subsoil by 1.48 °C and 1.34 °C, respectively. Additionally, snow removal increased SOC content by 8.27 % and 3.19 % and its stability by 53 % and 13.92 % in the topsoil and subsoil, respectively, and decreased microbial decomposition potential functioning by 55.89 % and 5.75 % in both soil layers. The three-dimensional spatial distribution of SOC and soil pores at the micro-scale indicated that snow removal significantly influenced pore structure and microbe feedback loops, thereby affecting SOC decomposition. Notably, snow removal led to an increase in the proportion of micropores by 3.44 % and 4.41 % in the topsoil and subsoil, respectively, suggesting enhanced protection of pore structure and preservation of SOC during decomposition processes. Overall, the findings suggest that snow removal may intensify the response of carbon pools to climate change in peatlands.

Optical Sensing of Tissue Freezing Depth by Sapphire Cryo-Applicator and Steady-State Diffuse Reflectance Analysis.

This work describes a sapphire cryo-applicator with the ability to sense tissue freezing depth during cryosurgery by illumination of tissue and analyzing diffuse optical signals in a steady-state regime. The applicator was manufactured by the crystal growth technique and has several spatially resolved internal channels for accommodating optical fibers. The method of reconstructing freezing depth proposed in this work requires one illumination and two detection channels. The analysis of the detected intensities yields the estimation of the time evolution of the effective attenuation coefficient, which is compared with the theoretically calculated values obtained for a number of combinations of tissue parameters. The experimental test of the proposed applicator and approach for freezing depth reconstruction was performed using gelatin-based tissue phantom and rat liver tissue in vivo. It revealed the ability to estimate depth up to 8 mm. The in vivo study confirmed the feasibility of the applicator to sense the freezing depth of living tissues despite the possible diversity of their optical parameters. The results justify the potential of the described design of a sapphire instrument for cryosurgery.