Effects of wildfire on the water chemistry of the northeastern part of the Great Vasyugan Mire (Western Siberia)

In this study, we determined the effect of wildfire in 2016 on the water chemistry of the northeastern drained part of the Great Vasyugan Mire. The influence of the pyrogenic factor on the water chemistry of the Great Vasyugan Mire was marked by an increase in concentrations of Na+, K+, Ca2+, Mg2+, Fetotal, SO4 2–, HCO3 –, NO– 3, Zn, Cu, Pb, and Cd. The maximum concentrations were observed in the spring (April) during the snow melting period, as well as during the rewetting period after the summer drought. In 2018–2019, there was a decrease in the concentration of the components in the waters after the fire in 2016 (SO4 2–, HCO3 –, NO– 3, Pb, Cd, Zn). An increase in the content of Na+, K+, Ca2+, Mg2+, NH+ 4, and Cu was noted, which is associated with the intensification of the processes of mineralisation of plant residues in the upper burnt peat layers.

Characteristic study of modified nano CuO powder-based paraffin composite and its experimental investigation of melting/solidification behavior for mobilized cold thermal storage systems

The low thermal conductivity of Phase Change Materials (PCM) reduces its performance and remains a challenging issue. In the present study, modified nano copper oxide powder (CuO) with various weight percentages is dispersed into paraffin wax to form Nano-PCM composites (NPCM). Transmission Electron Microscopy analysis showed the uniform dispersion of modified CuO and spherical in structure. Diffraction Scanning Calorimeter analysis (DSC) showed a trivial difference in the melting point of PCM and NPCM. The peak melting temperature of PCM was 18.56°C and for NPCM with 1% concentration was 17.14°C. The thermal conductivity of NPCM in solid and liquid states was high when compared to that of pure PCM. The thermal conductivity of NPCM with a 1% concentration is enhanced by 52% in a solid state and 20% in a liquid state. Solidification/Melting experiments conducted at different bath temperatures such as 15°C, 17°C, and 19°C for PCM and NPCM revealed that the solidification period and melting period reduced with an increase in concentrations of modified Nano CuO due to augmented heat transfer rates. The solidification time for NPCM with 1% concentration is reduced by 18.33% for discharging temperature 25°C, and melting time are reduced by 16.6% for charging temperature.

Ice Melt-Induced Variations of Structural and Functional Traits of the Aquatic Microbial Community along an Arctic River (Pasvik River, Norway)

The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria > Alphaproteobacteria > Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.

Behavior of Nitrogen in GH4169 Superalloy Melt during Vacuum Induction Melting Using Returned Materials

The nitrogen behavior of superalloy melt GH4169 during the vacuum induction melting (VIM) process was clarified by using different proportions of returned materials including block-shaped returned material, chip-shaped returned material, and pure materials to produce a high–purity superalloy melt and provide guidance for the purification of the superalloy melt. For the nitrogen removal during the VIM process, the denitrification rate in the refining period reached 10 ppm per hour on average, which is significantly higher than 1 ppm per hour on average in the melting period. The denitrification reaction of superalloy melt GH4169 under extremely low vacuum pressure is controlled by both the mass transfer of nitrogen in the melt and the chemical reaction of the liquid–gas interface. The nitrogen removal of superalloy melts during VIM occurs through the two methods of gasification denitrification and nitride floatation because the nitrides begin to precipitate in the liquid phase at 1550 °C. A higher nitrogen removal rate can be obtained by increasing the proportion of chip-shaped material or decreasing the proportion of block-shaped material.

Major Surface Melting over the Ross Ice Shelf, Antarctica

<p>West Antarctica (WA), especially the Ross Ice Shelf (RIS), has experienced more frequent surface melting during austral summer over the past three decades. Surface melting will jeopardize the stability of ice shelves and cause potential ice loss in the future. We investigate four major melt cases over the RIS via Polar WRF simulations driven by ERA5 reanalysis data and MODIS observed albedo. Direct warm air advection, recurring foehn effect, and cloud/upper warm air introduced radiative warming are the three major regional causes of surface melting over WA. Warm marine air can warm the ice surface directly. With significant moisture transport occurring over more than 40% of the time during the melting period, the impact from net radiation can be amplified via the formation of low-level liquid water clouds. Consequently, extensive downward longwave radiation favors the melting expansion over the middle and coastal RIS. Also, for 3 of 4 melt cases, more than 50% of the melting period experiences foehn warming, which can cause a 2 – 4 ºC increase in surface temperature. Isentropic drawdown is usually the dominant foehn mechanism and contributes a 14 ºC temperature increase, especially when strong low-level blocking occurs on the upwind side. Foehn clearance and decreasing surface albedo respectively increase the downward shortwave radiation and decrease the upward shortwave radiation, significantly contributing to surface melting in areas like western Marie Byrd Land. Moreover, frequent foehn cases can enhance the turbulent mixing on the leeside and benefit sensible heat transfer when Froude number is around 1. With better understanding of the regional factors for the surface melting, the prediction of the future stability of West Antarctic Ice Shelves will be improved.</p>

On the Seasonality of the Snow Optical Behaviour at Ny Ålesund (Svalbard Islands, Norway)

Polar areas are the most sensitive targets of climate change. From this perspective, the continuous monitoring of the cryosphere represents a critical need, which, now, we can only partially supply with specific satellite missions. The integration between remote-sensed multi-spectral images and field data is crucial to validate retrieval algorithms and climatological models. The optical behavior of snow, at different wavelengths, provides significant information about the microphysical characteristics of the surface in addition to the spatial distribution of snow/ice covers. This work presents the unmanned apparatus installed at Ny Ålesund (Svalbard) that provides continuous spectral surface albedo. A narrow band device was compared to a full-range system, to remotely sensed data during the 2015 spring/summer period at the Amundsen-Nobile Climate Change Tower. The system was integrated with a camera aimed to acquire sky and ground images. The results confirmed the possibility of making continuous observations of the snow surface and highlighted the opportunity to monitor the spectral variations of snowed surfaces during the melting period.

Examination of the Coating Method in Transferring Phase-Changing Materials

In this study, it is intended to identify the characteristics of heat regulation in heat storage microencapsulated fabrics and it is aimed to examine the effect of application method for microcapsules. For this purpose, phase-changing materials (PCM) microcapsules were applied according to the method of impregnation and coating on cotton fabrics. The presence and distribution of microcapsules on the fabric surface were investigated by scanning electron microscopy (SEM). The temperature regulation of the fabrics was examined utilizing the temperature measurement sensor and the data recorder system (Thermal camera). According to the DSC analysis, the melting process in fabrics coated with Mikrathermic P microcapsules occurred between 25.83oC - 31.04oC and the amount of heat energy stored by the cotton fabric during the melting period was measured as 2.70 J/g. Changes in fabric surface temperature due to the presence of microcapsules in the fabric structure were determined in the measurements. When comparing the transfer methods of PCM capsules, the contact angle of impregnated and coated fabric was obtained as 42o and 73o, respectively. As a result of the study, when the analysis results of the microcapsules transferred to the fabric by the impregnation and coating method are evaluated, it is seen that the PCM transferred fabric with the impregnation method performs more efficient temperature regulation. However, the analysis results show that fabrics transferred with PCM by coating also perform heat absorption, although not as much as the impregnation method. Performance evaluation according to the target properties of textile material will give the most accurate result for the fabrics which are treated by coating and impregnation method.

NDVI Variations and Its Responses to hydrothermal process in the Naqu River Basin, Qinghai-Tibet Plateau-Alpine Region

Extensive studies have been conducted over the whole year and various seasons to characterize the temporal and spatial changes in vegetation NDVI. However, there are few studies on the variations of NDVI in different soil hydrothermal processes of the alpine region. So we studied the spatial-temporal variation of vegetation cover and its responses to hydrothermal process in the Qinghai-Tibet Plateau-alpine region. Based on the GIMMS NDVI remote sensing images from 1982 to 2015, the temporal and spatial variations of NDVI in the Naqu river basin at different time scales were studied by using maximum synthesis method, and the linear regression. Results show that the vegetation has an overall degradation trend in the Naqu river basin, with primarily moderate and mild degradation degrees. Completely freezing period, completely melting period and freezing process period are the main vegetation degradation periods.

TECHNOLOGY FOR MAKING OF 12Х18Н10Т ALLOY IN INDUCTION-ARC FURNACES

A technology for making structural cryogenic steel 12Х18Н10Т from industrial waste has been developed. For it an induction plant was used which consists of two FS-series induction-arc furnaces. Problems of furnace charge preparation were considered: the fractional composition, oxidation, content of harmful impurities and a charging way. It made possible to ensure pot resistance and to decrease the melting period. Recommendations to decrease meniscus height on the melt surface are given.

Hydrometeorological Characteristics of Ice Jams on the Pemigewasset River in Central New Hampshire

Ice jams that occurred on the Pemigewasset River in central New Hampshire resulted in significant localized flooding on 26 February 2017 and 13 January 2018. Analyses of these two case studies shows that both ice jam events occurred in association with enhanced moisture transport characteristic of atmospheric rivers (ARs) that resulted in rain-on-snow, snowpack ablation, and rapid increases in streamflow across central New Hampshire. However, while the ice jams and ARs that preceded them were similar, the antecedent hydrometeorological characteristics of the region were different. The February 2017 event featured a “long melting period with low precipitation” scenario, with several days of warm (~5°–20°C) maximum surface temperatures that resulted in extensive snowmelt followed by short-duration, weak AR that produced ~10–15 mm of precipitation during a 6-h period prior to the formation of the ice jam. Alternatively, the January 2018 event featured a “short melting period with high precipitation” scenario with snowmelt that occurred primarily during a more intense and long-duration AR that produced >50 mm of rainfall during a 30-h period prior to the formation of the ice jam. Composite analysis of 20 ice jam events during 1981–2019 illustrates that 19 of 20 events were preceded by environments characterized by ARs along the U.S. East Coast and occur in association with a composite corridor of enhanced integrated water vapor > 25 mm collocated with integrated water vapor transport magnitudes > 600 kg m−1 s−1. Additional analyses suggest that most ice jams on the Pemigewasset River share many common synoptic-scale antecedent meteorological characteristics that may provide situational awareness for future events.