Melt Period Research Articles

Pot‐Cover Effect in Permafrost Embankment: In Situ Experiment Evidence and Mechanism Simulation

ABSTRACTUnder the influence of large temperature differences in an impermeable pavement layer of wide embankment in permafrost regions, liquid water accumulates at the bottom of the impermeable cover. The phenomenon is known as the pot‐cover effect and leads to an increase in soil water content and a reduction in bearing capacity of wide embankments. At present, water vapor and liquid water migrations and their effect on embankment thermal‐moisture stability have not been fully confirmed. To better understand the moisture transport and accumulation process within embankments, hydrothermal field monitoring was conducted from 2009 to 2011 on an asphalt concrete layer highway in Beiluhe, central Tibet Plateau. The field monitoring results show that soil moisture content between 50 and 250 cm below the pavement continuously increases with the number of freeze‐thaw cycles, with the largest increase during the 2 years being 6.4%. Then, a coupled hydro‐vapor‐thermal transport model was established and verified. Furthermore, the model was used to analyze the numerical recurrence of the pot‐cover effect. The simulation indicates that the upward migration of liquid water during the freezing period is less than the downward migration during the thawing period, while vapor migrates downward during the thawing period but upward during the freezing period. The migration of water vapor within the embankment during the freezing period is the main cause of the pot‐cover effect in permafrost regions. In addition, the research results can provide new ideas for understanding the internal mechanism of thermal‐moisture dynamics of the embankment and the stability prediction of permafrost engineering.

High resolution (1-km) surface soil moisture generation from SMAP SSM by considering its difference between freezing and thawing periods in the source region of the Yellow River

Soil moisture (SM) is a critical component of the land surface hydrological cycle, significantly impacting various sectors such as hydrology, meteorology, and agriculture. Accurate, high-resolution SM data are essential for effective flood forecasting, water resource management, and understanding the soil freeze-thaw processes in cold regions. This study aims to generate 1 km resolution liquid surface SM (SSM) data with a twice-daily update frequency by downscaling SMAP Level-4 SSM data using random forest (RF) and multiple linear regression (MLR) in the source region of the Yellow River (SRYR), by considering the differences in SM changes between freezing and thawing periods. To obtain the SSM data, 16 downscaling schemes of both RF and MLR were designed for each of the three scenarios. In each downscaling process, both land surface temperature (LST) and normalized difference vegetation index (NDVI) were utilized in MLR and RF models, alongside various combinations of additional variables such as albedo, elevation, leaf area index (LAI), soil texture. Results showed that during the freezing period, RF produced superior SSM estimates when supplemented with NDVI, LST, albedo, elevation, LAI, and soil texture. MLR was more effective during the thawing period when paired with NDVI, LST, elevation, LAI, and soil texture. During the freezing period, the downscaled SMAP SSM exhibited average R, RMSE, ubRMSE of 0.76, 0.029 m3·m-3, and 0.023 m3·m-3, respectively, when compared with in-situ measurements. During the thawing period, the average R, MAE, RMSE, and ubRMSE between the downscaled SMAP SSM and in-situ measurements were 0.52, 0.057 m3·m-3, 0.067 m3·m-3, and 0.054 m3·m-3, respectively, compared to 0.45, 0.070 m3·m-3, 0.083 m3·m-3, and 0.060 m3·m-3 for the original SMAP SSM. Thus, the research significantly enhances both the accuracy and spatial resolution of SMAP SSM estimations, underscoring its vital role in advancing hydrological studies within the SRYR.

Reducing CO2 emissions from rivers around bare land contributes to improving the carbon sink function of the Qinghai–Tibetan Plateau

River CO2 fluxes (FCO2) play an important role in the carbon cycle of the Qinghai‒Tibet Plateau (QTP). However, the carbon budget of river water is ignored in the assessment of the carbon sources and sinks of ecosystems on the QTP, which makes the assessment of the carbon sinks of ecosystems uncertain on the QTP. Here, we selected rivers around alpine steppe, alpine meadow, forestland and bare land areas on the QTP to determine their FCO2 values and control factors during thaw, rainy and freezing periods. The results revealed that river water around the alpine steppe absorbed CO2 during the thaw and freezing periods, making it a carbon sink. The influencing factors of FCO2 around different ecosystems significantly differed across the different periods. The pCO2 was the most direct factor affecting the FCO2 of river water. During the thaw period, the FCO2 of rivers around the alpine steppe and bare land was affected mainly by dissolved organic carbon (DOC) and precipitation, respectively. The FCO2 of rivers around the alpine meadow and forestland was affected by dissolved inorganic carbon (DIC). During the rainy period, the FCO2 of the rivers around the alpine steppe and bare land was affected mainly by total nitrogen (TN) and salinity, respectively. The FCO2 of rivers around the alpine meadow and forestland was affected by dissolved oxygen (DO) and DOC. During the freezing period, the FCO2 of the rivers around the alpine steppe and bare land was affected mainly by TN and pCO2, respectively. The FCO2 of rivers around the forestland and alpine meadow was affected by precipitation, runoff and DIC. The FCO2 in rivers around vegetated areas were affected by rock weathering, aquatic ecosystem biology and hydrological processes to varying degrees at different times. However, rivers around bare ground were less affected by these processes. The FCO2 values around the alpine steppe, alpine meadow, forestland and bare land were 1.40 g C/m2/d, 1.12 g C/m2/d, 2.29 g C/m2/d and 4.20 g C/m2/d, respectively. The river water around bare land released a large amount of CO2. Therefore, to reduce the CO2 emissions of rivers on the QTP, it is urgent that we restore bare-land vegetation and promote the transfer of bare land to steppe, which is an effective way to increase the carbon sink of the ecosystems on the QTP.

Hypoxia cycle in shallow lakes during winter (ice-covered to melting period): Stable and decay, hypoxia, and recovery phases

This study investigates hypoxic processes beneath lake ice and explores the interactions between water environmental factors and dissolved oxygen (DO) during winter, aiming to systematically assess the influence of winter climate changes on lake ecosystems through environmental variables (physical, chemical, and biological characteristics of water). A complete hypoxic cycle in a high-altitude shallow lake was recorded using high-frequency monitoring technology, and based on a predetermined hypoxic threshold (DO<2 mg/L), it was divided into three phases: stable and decay phase, hypoxic phase, and recovery phase. Significant trend changes of environmental variables under different levels of DO were analyzed for each phase using the Mann-Kendall non-parametric test. On the basis of evaluating the overall trend of the time series, a GAM multi-factor optimization model integrating interactive effects was constructed to explore the response mechanism of environmental variables to hypoxic processes. The optimized model showed excellent explanatory performance with R2 values of 0.833 for the stable and decay phase and 0.932 for the recovery phase, with AIC values of 1554.72 and 721.03, respectively. The trend test combined with model analysis indicates that: (1) the decay of DO under the ice is primarily affected by the increase in EC, BGA, and EC*Temp, (2) the phytoplankton biomass in shallow lakes during winter has a definite contribution to the occurrence of oxygen deficiency, and (3) the water body experiences rapid reoxygenation after the ice layer breaks, but the DO level is restricted by the increase in temperature. This study highlights the ecosystem characteristics of shallow ice-covered lakes in cold arid regions, advancing our understanding of the response relationship between hypoxic aquatic environments under ice and environmental factors.

Influence of low voltage programmed thawing on the quality of frozen pork and its myofibrillar protein

This study explored the effects of low voltage programmed thawing (LVPT) on thawing period, water status, current density as well as physicochemical properties of porcine longissimus dorsi muscle, considering air thawing (AT), water immersion thawing (WT) and cold storage thawing (CST) for the comparison, additionally making fresh meat (FM) as the control. The thawing process used current limiting to gradually reduce the maximum output current to 500, 200 and 100 mA, respectively, by applying a safe voltage of 35 V in a home defrosting apparatus. Using two pairs of foil plate, the thawing (LVPT-2) with dual current loop accelerated the melting of ice crystals than the process with one pair of polar plate (LVPT-1) with one current loop. From −18 °C to −1 °C, the thawing period of LVPT-2 was reduced by 14.54 %, 11.72 %, and 15.95 % compared with that of LVPT-1 for samples within the thickness of 2, 3 and 4 cm, respectively. During the process, the intensity and density of the current loaded on the frozen meat gradually increased. LVPT-1 retained water and reduced its migration inside the meat, and protein solubility was better maintained. As the thickness increased, the effect of LVPT-2 on the moisture distribution and protein solubility of the sample decreased. LVPT-1 treatment resulted in less fat oxidation as well as stable secondary and tertiary structures of myofibrillar proteins compared to other treatments. At low voltage, the ability of LVPT −2 to maintain meat quality was reduced due to the increase in current density. In addition, LVPT-1 reduced muscle damage because of rapid melting of ice crystals. In contrast, LVPT-2 was conductive the formation of hot spots due to dual current loop passed through the pork in final phase of thawing, which would adversely influence the quality of thawed meat. Finally, LVPT could improve the rate of thawing, water binding capacity and meat quality, especially, there was no overheating effect on the meat because of current limiting.

Thermal performance and flash point analyses of concentrator photovoltaic (CPV) system using multiple types of PCMs and various panel inclination angles under the effect of a constant heat flux

This numerical study conducts a comparative analysis of various phase change materials (PCMs) including Lauric Acid, Paraffin, RT 24, RT 31, RT 35, RT 38, RT 42, RT 47, RT 50, and Lithium Nitrate Trihydrate (LiNO3.3H2O) to assess their suitability for optimizing the thermal management of a solar concentrator photovoltaic (CPV) system. The analysis focuses on the temperature regulation capabilities, melting dynamics of the used PCMs, along the electrical efficiency of the CPV system across a range of inclination angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) under a constant heat flux of 1000 W/m². The research aims to identify the most effective solutions for enhancing the efficiency and reliability of solar concentrator systems. Key considerations such as PCM’s flash points, liquid fraction and convective behavior are addressed for each PCM type. Numerical results obtained using ANSYS Fluent indicate that Lithium Nitrate Trihydrate (LiNO3.3H2O) outperformed most paraffin-based PCMs, such as RT 24 and RT 35, with around 24 % higher electrical efficiency. Although Lauric Acid was approximately 19.5 % less efficient than Lithium Nitrate Trihydrate, it offered superior long-term thermal stability due to its slower melting rate and phase change temperature of 43–44°C, taking 45.33 % longer to melt compared to Paraffin RT 24. RT 50, with its higher melting temperature of 50°C, provided a balance between melting period and efficiency, making it an ideal PCM for applications requiring both moderate efficiency and sustained thermal regulation.

HIGH-RESOLUTION SATELLITE ESTIMATION OF SNOW COVER FOR FLOOD ANALYSIS IN EAST KAZAKHSTAN REGION

The increasing frequency of extreme weather events linked to climate change has made flood forecasting an important issue, particularly in mountainous regions where snowmelt is a major driver of seasonal flooding. This study explores the application of snow cover estimation techniques to assess snowmelt dynamics and their potential impact on flood risks in the Ulba and Uba basins in East Kazakhstan. To achieve this, high-resolution multispectral satellite imagery from the Sentinel-2 Surface Reflectance dataset is used, focusing on images collected between March and October for the years 2021 to 2024. The images are processed in Google Earth engine platform with strict filtering based on spatial intersection with the basins and cloud cover pixels percentage, ensuring high-quality data for snow cover analysis. The study utilizes multiple remote sensing indices for snow cover estimation. The normalized difference snow index is calculated using the green and shortwave infrared bands to detect snow-covered pixels. Fractional snow-covered area is derived from the NDSI using the 'FRA6T' relationship, offering a more nuanced estimate of snow distribution across the basins. Additionally, a near-infrared to shortwave infrared ratio threshold is employed to minimize confusion between snow and water, improving the detection of snow cover, particularly in regions near water bodies or during melt periods. The resulting snow cover maps and fSCA estimates provide a detailed picture of snow distribution and melt dynamics, contributing to the assessment of snowmelt’s role in flood risk development. The obtained insights can assist in refining flood forecasting models, improving early warning systems, and supporting informed water resource management in vulnerable regions.

A new framework for assessing carbon fluxes in alpine rivers

Riverine carbon dynamics connecting land and ocean carbon cycles play a crucial role in regulating global carbon turnover. Despite its importance, the impact of climate change and runoff components on riverine carbon dynamics, particularly in alpine regions, remains underexplored. In this study, we introduce a conceptual framework to assess the impact of climate change on riverine carbon fluxes across various runoff components. We use a distributed hydrological model and stable isotopes to identify key runoff components, then identify the dominant drivers of variability in runoff carbon concentrations. We establish component-specific relationships between carbon concentrations and dominant drivers, assessing the watershed carbon balance through a comparative analysis of carbon fluxes in various runoff components. The proposed framework was validated in a representative watershed on the Qinghai-Tibet Plateau, and it effectively captured the seasonal carbon dynamics and the impact of climate change and runoff components. Our results indicated that runoff and temperature dominate riverine carbon concentrations. The carbon fluxes associated with rainfall and groundwater showed higher sensitivity to runoff, while those in the snowmelt component were more sensitive to temperature. We found seasonal variability in carbon fluxes, with particulate organic carbon concentrations peaking at 4.80 mgC/L during the thawing period and other carbon components (i.e., dissolved organic carbon, dissolved inorganic carbon, particulate inorganic carbon) peaking during the freezing period. We quantified the total carbon input and output for the watershed as 15.12 tC/km2/yr and 12.19 tC/km2/yr, with 51.2% of the carbon influx attributed to rainfall, 10.9% to groundwater, and 37.9% to snowmelt. Our study enhances the understanding of riverine carbon dynamics and offers a promising approach for predicting carbon budgets under climate change.

Ethnic Relations between Lithuanians and Poles in the Eastern and South-Eastern Part of Lithuania 1960–1985

The article explores the manifestation of the Soviet national policy in the eastern and south-eastern part of Lithuania during the Khrushchev Thaw period and the Brezhnev Era of stagnation by focusing on the ethnic relations between Lithuanian and Poles who, in terms of numbers, dominated in the region. The situation in the eastern and south-eastern part of Lithuania (multi-ethnic population, geographical location, historical heritage, etc.) was very favourable for the implementation of the Soviet national policy. Based on the slogans of “friendship between nations” and “internationalism”, the concept of the convergence of the nations was realised. It manifested in closer relations between various ethnic groups, soviet republics and their population. As far as eastern and south-eastern part of Lithuania was concerned, relationships were promoted with neighbouring republics, firstly with Belarus, rather than with other regions of the Republic of Lithuania. Such policy led to the formation of a specific situation in Vilnius region. A certain part of the inhabitants of the region more often identified themselves with the Belarusian population and had a poor understanding of the life of other regions in Lithuania. This determined segregation between the Lithuanian and Polish communities, and alienation of the Poles. The Soviet authorities controlled ethnic relations between Lithuanians and Poles; any potential ethnic tension was immediately repressed and hardly ever surfaced. Ethnic disagreements between Lithuanians and Poles (due to different interpretation of historical past, etc.) were frozen for several decades and broke out only at time of the decline of the Soviet period. The position of the Polish population in the region was fuelled by attention and support from the Polish authorities and society. However, only relationships sanctioned by the Soviet authorities were allowed. Therefore any nationalist ideas from Poland were immediately stifled. Seeking faster indoctrination of the population, the Soviet authorities used the Polish language factor in the eastern and south-eastern part of Lithuania. The Polish population in this region was provided an opportunity to develop education and culture in their mother tongue, yet this was controlled and Sovietised. The support for nurturing the Polish ethnic identity by the Soviets formed a stereotype among Lithuanians that Poles were protected and the eastern and south-eastern part of Lithuania was deliberately Polonised. In the 1970s, when attempts to consolidate the society in the USSR were made on the basis of the Russian language and culture, assimilation efforts (Russification) strengthened in Lithuania. This process particularly affected the position of the Poles in the eastern and south-eastern part of Lithuania (Polish schools became Russian schools, the number of mixed marriages increased, the Russian language was increasingly used for communication, etc.). Such policies led to the assimilation of certain part of the Polish population in the region.

Insights into the shallow landslide mechanism of expansive soil slope induced by freeze-thaw cycles and snowmelt infiltration

For rigorous understanding the shallow landslide mechanisms and deformation characteristics of expansive soil slopes, a comprehensive in-situ monitoring platform is established. Triaxial creep tests and microstructure analysis with scanning electron microscopy (SEM) are also conducted on expansive soil samples obtained from Binxi station. Field monitoring data indicates that freeze-thaw (F-T) cycle and snowmelt infiltration significantly increase the creep deformation of expansive soil slope during spring melting period. Due to the influence of F-T cycle and snowmelt infiltration, more soil grains are involved in the shear deformation contributing to a large, localized shearing. Additionally, the microstructural analysis shows that F-T cycle influence the relationship between expansive soil grains that gradually change from face-face contact to point-face contact or edge-edge contact form. The shallow landslide mechanisms of expansive soil slope are revealed from creep deformation and microstructure characteristics of soils after the F-T cycle and snowmelt infiltration, which can be summarized into two stages, namely, the snowfall accumulation state and snow melt-shallow infiltration stage. These results can serve as a good reference for the prevention of expansive soil slopes in seasonally frozen regions.

Variation in Glacier Albedo on the Tibetan Plateau between 2001 and 2022 Based on MODIS Data

Albedo is a primary driver of the glacier surface energy balance and consequent melting. As glacier albedo decreases, it further accelerates glacier melting. Over the past 20 years, glaciers on the Tibetan Plateau have experienced significant melting. However, our understanding of the variations in glacier albedo and its driving factors in this region remains limited. This study used MOD10A1 data to examine the average characteristics and variations in glacier albedo on the Tibetan Plateau from 2001 to 2022; the MOD10A1 snow cover product, developed at the National Snow and Ice Data Center, was employed to analyze spatiotemporal variations in surface albedo. The results indicate that the albedo values of glaciers on the Tibetan Plateau predominantly range between 0.50 and 0.60, with distinctly higher albedo in spring and winter, and lower albedo in summer and autumn. Glacier albedo on the Tibetan Plateau decreased at an average linear regression rate of 0.06 × 10−2 yr−1 over the past two decades, with the fastest declines occurring in autumn at an average rate of 0.18 × 10−2 yr−1, contributing to the prolongation of the melting period. Furthermore, significant variations in albedo change rates with altitude were found near the snowline, which is attributed to the transformation of the snow and ice surface. The primary factors affecting glacier albedo on the Tibetan Plateau are temperature and snowfall, whereas in the Himalayas, black carbon and dust primarily influence glacier albedo. Our findings reveal a clear decrease in glacier albedo on the Tibetan Plateau and demonstrate that seasonal and spatial variations in albedo and temperature are the most important driving factors. These insights provide valuable information for further investigation into surface albedo and glacier melt.

Chestnut soil organic carbon is regulated through pore morphology and micropores during the seasonal freeze–thaw process

Soil aggregates are basic structural units in soil organic carbon (SOC) protection. In alpine ecosystems, the seasonal freeze–thaw (FT) process characterizes soil formation and nutrient cycling. However, previous studies were mostly based on simulated FT experiments, which amplified the effects of natural FT processes. And, the regulations of pore structure on SOC protection/loss of aggregates during the FT processes were still not well understood. To investigate the effect of the seasonal FT process on SOC and pore structure of aggregates, as well as the interactions among them, soil samples were selected during a whole seasonal FT cycle, which can be divided into four periods: unstable freezing (UFP), stable frozen (SFP), unstable thawing (UTP), and stable thawed periods (STP). The results demonstrated that freezing increased SOC concentration as the total organic carbon (TOC) content of all aggregate fractions peaked in the SFP (17.46 g/kg on average). The TOC content of aggregates in the UFP dropped to 7.91 g/kg on average, which revealed a dramatic SOC loss after thawing began. Thawing also decreased the proportions of particulate organic carbon (POC) compared with mineral-associated organic carbon (MAOC). The highest microbial abundance was also found in the SFP. Freezing promoted the formation of pores > 80 μm while thawing increased the regularity of pore morphology. Pore structure explained 48.77 % of the SOC variance in the thawing period, but only 19.29 % of that in the freezing period. Overall, in the freezing process, soil pore structure impacted the SOC input by mediating pore morphology. In the thawing process, soil pore structure inhibited SOC loss by enhancing the formation of pores < 15 μm. These results demonstrate new perspectives on the soil aggregate microstructure–microbe–SOC interactions.

Coastal Sea Ice Concentration Derived from Marine Radar Images: A Case Study from Utqiaġvik, Alaska

We apply the Canny edge algorithm to imagery from the Utqiaġvik coastal sea ice radar system (CSIRS) to identify regions of open water and sea ice and quantify ice concentration. The radar-derived sea ice concentration (SIC) is compared against the (closest to the radar field of view) 25 km resolution NSIDC Climate Data Record (CDR) and the 1 km merged MODIS-AMSR2 sea ice concentrations within the ∼11 km field of view for the year 2022–2023, when improved image contrast was first implemented. The algorithm was first optimized using sea ice concentration from 14 different images and 10 ice analysts (140 analyses in total) covering a range of ice conditions with landfast ice, drifting ice, and open water. The algorithm is also validated quantitatively against high-resolution MODIS-Terra in the visible range. Results show a correlation coefficient and mean bias error between the optimized algorithm, the CDR and MODIS-AMSR2 daily SIC of 0.18 and 0.54, and ∼−1.0 and 0.7%, respectively, with an averaged inter-analyst error of ±3%. In general, the CDR captures the melt period correctly and overestimates the SIC during the winter and freeze-up period, while the merged MODIS-AMSR2 better captures the punctual break-out events in winter, including those during the freeze-up events (reduction in SIC). Remnant issues with the detection algorithm include the false detection of sea ice in the presence of fog or precipitation (up to 20%), quantified from the summer reconstruction with known open water conditions. The proposed technique allows for the derivation of the SIC from CSIRS data at spatial and temporal scales that coincide with those at which coastal communities members interact with sea ice. Moreover, by measuring the SIC in nearshore waters adjacent to the shoreline, we can quantify the effect of land contamination that detracts from the usefulness of satellite-derived SIC for coastal communities.

Metal(loid)s Removal Response to the Seasonal Freeze–Thaw Cycle in Semi-passive Pilot Scale Bioreactors

There is an increasing demand for cost-effective semi-passive water treatment that can withstand challenging climatic conditions and effectively and sustainably manage mine-impacted water in (sub)arctic regions. This study investigated the ability of four pilot-scale bioreactors inoculated with locally sourced bacteria and affected by a freeze–thaw cycle to remove selenium and antimony. The bioreactors were operated at a Canadian (sub)arctic mine for a year. Two duplicate bioreactors were installed in a heated shed that was maintained at 5 °C over the winter, while two other duplicates were installed outdoors and left to freeze. The removal rate of selenium and antimony was monitored weekly, while a genomic characterization of the microbial populations in the bioreactors was performed monthly. The overall percentage of selenium and antimony removal was similar in the outside (10–93% Se, 20–96% Sb) and inside (35–94% Se, 10–95% Sb) bioreactors, apart from the spring thawing period when removal in the outdoor bioreactors was slightly lower for Se. The dominant taxonomic groups of microbial populations in all bioreactors were Bacteroidota, Firmicutes, Desulfobacterota and Proteobacteria. The microbial population composition was consistent and re-established quickly after spring thaw in the outside bioreactors. This demonstrated that the removal capacity of bioreactors inoculated with locally sourced bacteria was mostly unaffected by a freeze–thaw cycle, highlighting the strength of using local resources to design bioreactors in extreme climatic conditions.

Thermodynamic modeling of cobalt and nickel reduction using hydrometallurgical enrichment concentrates for steel alloying

The article provides studies on reduction processes in model thermodynamic systems and processes of nickel reduction from nickel concentrate and cobalt and nickel from cobalt-nickel concentrate. Concentrates are obtained during hydrometallurgical enrichment of polymetallic manganese-containing ores of the Kemerovo region – Kuzbass. By thermodynamic modeling using TERRA software complex, it was determined that nickel can be completely reduced from oxide in the NiO – C system at a carbon consumption of 0.08 kg/kg NiO, and at a carbon consumption of 0.15 kg/kg NiO ‒ in the NiO – Fe2O3 – C system. It was found that cobalt reduction in the CoO – C system begins at a temperature of about 513 K at any carbon consumption. With a further increase in temperature, the reduction process depends only on consumption of the reducing agent. From the obtained thermodynamic modeling data, it follows that cobalt reduction from the cobalt-nickel concentrate begins at a temperature of about 513 K and subsequently depends slightly on temperature. The extraction of cobalt increases with the amount of reducing agent at temperatures up to 553 K, then remains constant up to 1473 K temperature. Nickel reduction takes place at a temperature above 473 K. The degree of nickel reduction slightly depends on the temperature and amount of reducing agent at consumption of the latter over 0.02 kg/kg of concentrate. Laboratory studies showed that during the melting period, nickel can be reduced from its oxide almost completely with solid carbon, since nickel has less sensitivity to oxygen than iron. Theoretical and experimental studies of steel direct alloying showed that it is advisable to use a solid phase process in reduction of nickel and cobalt. Nickel concentrate and cobalt-nickel concentrate during steel smelting in an electric furnace is advisable to be introduced into charge in the form of mixtures pelletized with a carbonaceous reducing agent.

Moscow Palace of Pioneers in the Cinema: A History Frozen in Time

The Moscow Palace of Pioneers on the Vorobyovy Gory — an architectural monument of Soviet modernism, the most successful and recognizable building of the Thaw period — can be found in many Soviet and Russian films: “The Tale of Lost Time”, “Gimme the Book of Complaints”, “Moscow — Cassiopeia”, “The Way to the Concert”, “Afonya”, “Dangerous Age”, “Nina”, “Legend No. 17”, “Thaw”, “Lyudmila Gurchenko”, “The Optimists” and others. The article reviews filming locations of feature and documentary films, identifies the main locations of the director’s groups, parallels and comparisons of perspectives in cinema with contemporary reality. The reasons for the director’s choice of certain halls, auditoriums, and spaces are analyzed; changes in the role and functionality of the spaces are identified; and the connection with the plot is traced. It is shown how, thanks to the artistic language of cinema, the directors change the function of buildings and spaces: the seventh building becomes an airport, the winter garden becomes a billiard room, classrooms become editorial offices, the theatre hall becomes a meeting place for diplomats. Some films depict unique interiors of the Palace, panels and mosaics, while in other films the directors were interested in innovative objects and angles that were not clearly linked to the pioneer theme. Many of the reviewed films contain a pedagogical component: they teach to value time (The Tale of Lost Time), to dream (Moscow is My Love), to set high goals (Moscow — Cassiopeia), to keep one’s word (Thaw), to succeed (Legend No. 17, Lyudmila Gurchenko), to seek the right path in life (Afonya), to be a patriot (The Optimists). Documentary films about the Moscow Palace of Pioneers are a vivid example of successful organisation of the educational process. The article may be interesting and useful to researchers of the spheres of culture, cinema, art, history and education, residents and guests of the capital and everyone who is interested in the history of the Moscow Palace of Pioneers. The materials of the research are also of practical value and can be used by tour guides, teachers, methodologists and teachers.

Effects of Freeze−Thaw Cycles on Available Nitrogen Content in Soils of Different Crops

In order to study the effect of freeze−thaw cycles on the content of available nitrogen in soils of different crops and obtain an in-depth understanding of changes in soil fertility and soil environment in cold regions, a laboratory simulation experiment was conducted with different freeze−thaw times, temperature differences, and periods. The changes in available nitrogen concentrations in the 0–15 cm and 15–30 cm layers of corn, vegetable, and paddy soils were measured by the alkaline-hydrolysis diffusion method. The results were as follows. (1) The freeze−thaw process had significant effects on the available nitrogen content in the three soils. Under the treatment with different numbers of freeze−thaw cycles, the available nitrogen content in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum values at the 8th, 1st, and 3rd freeze−thaw cycle, at 156.92 mg/kg, 479.17 mg/kg and 181.75 mg/kg, respectively; the available nitrogen content decreased slowly after reaching the maximum value. (2) Under the freeze−thaw temperature-difference treatment, the available nitrogen concentration in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum value at a temperature difference of 30 °C, at 147 mg/kg, 476 mg/kg and 172.5 mg/kg, respectively, and the available nitrogen content of the 15–30 cm soil layers changed slightly. (3) Under different freeze−thaw periods, the magnitudes of the changes in soil available nitrogen concentration in 0–15 cm of corn soil and paddy soil were, in descending order, short-term freezing and long-term melting &gt; long-term freezing and long-term melting &gt; short-term freezing and short-term melting &gt; long-term freezing and short-term melting. The soil available nitrogen concentration at different depths in the vegetable soil reached the maximum value under the treatment with long-term freezing and short-term melting. (4) The available nitrogen content of paddy soil under the high-water-content condition was higher than that of paddy soil under the low-water-content condition, and the change in available nitrogen content was more obvious under the high-water-content condition under different freeze−thaw period treatments; the opposite was true for corn soil and vegetable soil. Simulation studies on rapid changes in soil nitrogen content during tests that simulate winter freeze−thaw conditions are important for understanding crop growth, the application of nitrogen fertilizer in spring, and the prevention of surface-water pollution from agricultural runoff.

Macro–micro correlation analysis on the loess from Ili River Valley subjected to freeze–thaw cycles

The Ili River Valley in Xinjiang, China, is a typical seasonal frozen area where loess landslide disasters have become increasingly common during the freeze–thaw periods in recent years. This study analyzed the macroscopic mechanical strength and microstructure changes of the Ili loess under different freeze–thaw cycles (FTCs) through the post-freeze–thaw triaxial compression test on the unsaturated soil in laboratory. Apart from the scanning electron microscopy (SEM), and the nuclear magnetic resonance (NMR), the macro–micro correlation analysis and the cluster-principal component analysis were applied for the theoretical discussion. The results indicated that the cohesive force of the loess exhibits an initial decreases, followed by the increases, and eventually keep stable after various FTCs, while the internal friction angle showed the opposite developing trend before the final constant. Similar to the strong correlation between the cohesive force and the particle abundance, the internal friction angle is also closely related to the abundance and orientation fractal dimension of the loess particles. However, the principal component analysis results showed that cohesive force strongly correlates with the average maximum pore size and the pore size fractal dimension, for which the internal friction angle most strongly affected by the average maximum particle size. The possible reason is that the extracted principal components represent a class of microscopic parameters with the same or similar change trend, although there may be a certain offset between them. The mechanical deterioration of loess is attributed to the repeated frost heaving force and the migration potential caused by FTCs. The alterations of the microstructure accelerated the deterioration of the macroscopic mechanical properties of the loess, which further widens the understanding of the mechanism behind the deterioration of loess mechanical strength in the Ili River Valley under FTCs, and contributes to the prevention and management of the local landslide disasters.

Seasonal variations in the contribution of zooplankton fecal pellets to the particulate organic carbon fluxes over the slopes of the Pacific Arctic region

As part of the Korea Arctic Mooring System (KAMS), sequential sediment traps were deployed at KAMS1 over the East Siberian Sea slope (∼115 and ∼335 m) and at KAMS2 over the Chukchi Sea slope (325 m) to collect sinking particles from August 2017 to August 2019. Fecal pellet carbon (FPC) fluxes and their contribution to the particulate organic carbon (POC) fluxes were measured to assess the role of zooplankton fecal pellets in the biological carbon pump at both sites. FPC fluxes increased at the onset of an under-ice bloom and peaked during the melt period at both sites in 2018. At KAMS1, a remarkable increase in FPC fluxes reflected the enhanced grazing of large copepods during the anomalously productive spring and summer of 2018, however their contributions to the POC fluxes mostly remained <10%. At KAMS2, relatively low FPC fluxes during the under-ice bloom suggested the export of a larger proportion of pellets produced by small copepods. Sustained FPC fluxes from January to May 2018 at KAMS2 contributed up to 24% of the POC fluxes, possibly resulting from pellet production by overwintering copepods grazing on particles laterally transported into the region in the presence of ice. These results indicate that despite their limited contribution to the POC fluxes, FPC fluxes varied with food availability, zooplankton community structure, and hydrographic conditions over the East Siberian and Chukchi Sea slopes.

Impact of freeze–thaw cycling on the stability and turnover of black soil aggregates

During freeze–thaw cycling, aggregates undergo a dynamic change in breakdown–formation (turnover), however, how the turnover occurs between aggregates of various particle sizes is not clear. To clarify the influence of freeze–thaw cycling on the dynamic changes in the particle size of soil aggregates, soil aggregates from the Black Soil Region of Northeast China were selected as the research objects. The study conducted in situ dynamic monitoring experiments, innovatively applying the rare earth oxide (REO) tracer method to natural conditions of freeze–thaw cycles (autumn freeze–thaw period, freezing period, and spring freeze–thaw period), accurately tracking the turnover paths and quantifying the turnover rates between aggregates of various particle sizes. The results revealed that the total value of the formation paths of the 2–5 mm aggregates and 0.25–2 mm aggregates increased during the autumn freeze–thaw period. The number of freeze–thaw cycles and accumulated snowfall were significantly positively correlated with aggregate stability, with an increase in the number of freeze–thaw cycles and accumulated snowfall resulting in an increase in the proportion of aggregates > 0.25 mm, which improved aggregate stability. In addition, the total value of the breakdown path of macro-aggregates increased during the spring freeze–thaw cycling period. Soil moisture was significantly negatively correlated with aggregate stability, with increased soil moisture resulting in a decrease in the percentage of aggregates > 0.25 mm, which resulted in a decrease in aggregate stability. The study can provide a reference understanding for the effects of freeze–thaw cycles on the structure of black soil and provide a theoretical basis for improving the quality of arable land.