ESEM Methodology for the Study of Ice Samples at Environmentally Relevant Subzero Temperatures: “Subzero ESEM”

2021 ◽  
pp. 1-14
Author(s):  
Kamila Závacká ◽  
Vilém Neděla ◽  
Eva Tihlaříková ◽  
Pavla Šabacká ◽  
Jiří Maxa ◽  
...  
Keyword(s):  
Thermodynamic Equilibrium ◽  
Atmospheric Chemistry ◽  
Food Industry ◽  
Ice Formation ◽  
Environmental Scanning ◽  
Ansys Software ◽  
Natural Conditions ◽  
Subzero Temperatures ◽  
Surface Ice ◽  
Ice Sublimation

Abstract Frozen aqueous solutions are an important subject of study in numerous scientific branches including the pharmaceutical and food industry, atmospheric chemistry, biology, and medicine. Here, we present an advanced environmental scanning electron microscope methodology for research of ice samples at environmentally relevant subzero temperatures, thus under conditions in which it is extremely challenging to maintain the thermodynamic equilibrium of the specimen. The methodology opens possibilities to observe intact ice samples at close to natural conditions. Based on the results of ANSYS software simulations of the surface temperature of a frozen sample, and knowledge of the partial pressure of water vapor in the gas mixture near the sample, we monitored static ice samples over several minutes. We also discuss possible artifacts that can arise from unwanted surface ice formation on, or ice sublimation from, the sample, as a consequence of shifting conditions away from thermodynamic equilibrium in the specimen chamber. To demonstrate the applicability of the methodology, we characterized how the true morphology of ice spheres containing salt changed upon aging and the morphology of ice spheres containing bovine serum albumin. After combining static observations with the dynamic process of ice sublimation from the sample, we can attain images with nanometer resolution.

Effects of lead width variation, re-freezing and mixing events on lead water structure in the central Arctic

2021 ◽  
Author(s):  
Daiki Nomura ◽  
Alison Web ◽  
Yuhong Li ◽  
Manuel Dall’osto ◽  
Katrin Schmidt ◽  
...  
Keyword(s):  
Vertical Structure ◽  
Lower Boundary ◽  
Water Structure ◽  
Sampling Period ◽  
Ice Formation ◽  
Layer Surface ◽  
Mixing Process ◽  
Survey Period ◽  
Mixing Processes ◽  
Surface Ice

<p>We undertook a lead survey during the international drift campaign MOSAiC, Leg 5 (from 22 August to 17 September 2020) to understand the effects of lead width variation, re-freezing, and mixing events on lead water vertical structure. At the beginning of the survey period, the freshwater layer was occupied for the top 1 m depth and there were strong vertical gradients in temperature, salinity, and dissolved oxygen (DO) within 1 m depth: from 0.0°C to –1.6°C for temperature, from 0.0 to 31.4 psu for salinity, and 10.5 to 13.5 mg L<sup>–1</sup> for DO. A strong DO minimum layer corresponded with a salinity of 25 psu, and usually occurred at the freshwater–seawater interface at approx. 1 m depth, most likely as a result of an accumulation of organic matter and ongoing degradation/respiration processes at this interface. However, during the survey period, these strong gradients weakened and reduced the freshwater layer thickness (FLT). In the first half of the sampling period (until 4 September), FLT changed due to variations in lead width: as lead width increased, FLT decreased due to a stretching of the freshwater layer. In the second half of the sampling period, FLT was controlled by the surface ice formation (re-freezing) and mixing processes along the lower boundary of the freshwater layer. Surface ice formation removed freshwater and the formation of surface ice (about 0.2 m thick) explains 20% of the reduction of FLT. The remaining 80% of the reduction of FLT was due to the mixing process within the water column that was initiated by cooling and re-freezing. This mixing process diluted the salinity from 31.6 to 29.3 psu in the water below freshwater layer towards the end of the survey period. Our results indicate that lead water structure can change rapidly and dynamically and that this has significant effects on the biogeochemical exchange between lead systems and the atmosphere.</p>

Fish Antifreeze Proteins: Recent Gene Evolution

1986 ◽  
Vol 43 (5) ◽  
pp. 1028-1034 ◽  
Author(s):  
Gary K. Scott ◽  
Garth L. Fletcher ◽  
Peter L. Davies
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Genomic Organization ◽  
Gene Evolution ◽  
Antifreeze Proteins ◽  
Gene Organization ◽  
Ice Formation ◽  
Polar Regions ◽  
Subzero Temperatures ◽  
Combining Evidence

A variety of antifreeze proteins is produced by marine teleosts inhabiting polar regions to ensure protection from internal ice formation at subzero temperatures. Combining evidence from paleoclimatology, teleostian evolution, and studies of antifreeze gene organization, the case is made for Cenozoic cooling as the force driving antifreeze evolution in marine teleosts. The distribution of antifreeze types amongst teleost suborders, families, genera, and species correlates with Cenozoic glaciation in the Southern Hemisphere preceding that in the Northern Hemisphere by approximately 25 million yr. The genomic organization of antifreeze genes suggests recent and extensive amplification, an event compatible with their proposed stress-induced origin. Also, a realignment of the nototheniids with the Gadiformes based on antifreeze protein data is suggested.

scholarly journals Ice formation on lake surfaces in winter causes warm-season bias of lacustrine brGDGT temperature estimates

2020 ◽  
Vol 17 (9) ◽  
pp. 2521-2536 ◽  
Author(s):  
Jiantao Cao ◽  
Zhiguo Rao ◽  
Fuxi Shi ◽  
Guodong Jia
Keyword(s):  
Lake Water ◽  
Physical Phenomenon ◽  
Warm Season ◽  
Northern China ◽  
Ice Formation ◽  
High Latitudes ◽  
Study Region ◽  
Bottom Waters ◽  
The Mean ◽  
Surface Ice

Abstract. It has been frequently found that lacustrine branched glycerol dialkyl glycerol tetraethers (brGDGT)-derived temperatures are warm-season-biased relative to measured mean annual air temperature (AT) in the middle to high latitudes, the mechanism of which, however, is not very clear. Here, we investigated the brGDGTs from catchment soils, suspended particulate matter (SPM) and surface sediments in different water depths in Gonghai Lake in northern China to explore this question. Our results showed that the brGDGT distribution in sediments resembled that in the SPM but differed from the surrounding soils, suggesting a substantial aquatic origin of the brGDGTs in the lake. Moreover, the increase in brGDGT content and decrease in methylation index with water depth in sediments suggested more contribution of aquatic brGDGTs produced from deep or bottom waters. Therefore, established lake-specific calibrations were applied to estimate local mean annual AT. As usual, the estimates were significantly higher than the measured mean annual AT. However, they were similar to (and thus actually reflected) the mean annual lake water temperature (LWT). Interestingly, the mean annual LWT is close to the measured mean warm-season AT, thus suggesting that the apparent warm-season bias of lacustrine brGDGT-derived temperatures could be caused by the discrepancy between AT and LWT. In our study region, ice forms at the lake surface during winter, leading to isolation of the underlying lake water from air and hence higher LWT than AT, while LWT basically follows AT during warm seasons when ice disappears. Therefore, we think that lacustrine brGDGTs actually reflected the mean annual LWT, which is higher than the mean annual AT in our study location. Since the decoupling between LWT and AT in winter due to ice formation is a universal physical phenomenon in the middle to high latitudes, we propose this phenomenon could be also the reason for the widely observed warm-season bias of brGDGT-derived temperatures in other seasonally surface ice-forming lakes, especially in shallow lakes.

scholarly journals Evaporating brine from frost flowers with electron microscopy, and implications for atmospheric chemistry and sea-salt aerosol formation

2017 ◽  
Author(s):  
Xin Yang ◽  
Vilém Neděla ◽  
Jiří Runštuk ◽  
Gabriela Ondrušková ◽  
Ján Krausko ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Ambient Air ◽  
Sea Salt ◽  
Heterogeneous Reactions ◽  
Environmental Scanning ◽  
Aerosol Formation ◽  
Ice Surface ◽  
Spatial Dimensions ◽  
Frost Flowers ◽  
External Forces

Abstract. An environmental scanning electron microscope was used for the first time to obtain well-resolved images, in both temporal and spatial dimensions, of lab-prepared frost flowers (FFs) under evaporation within the chamber temperature range from −5 °C to −18 °C and pressures above 500 Pa. Our scanning shows temperature-dependent NaCl speciation: the brine covering the ice was observed at all conditions, whereas the NaCl crystals were formed at temperatures below −10 °C as the brine oversaturation was achieved. Finger-like ice structures covered by the brine, with a diameter of several micrometres and length of tens to one hundred micrometres, are exposed to the ambient air. The brine-covered fingers are highly flexible and cohesive. The exposure of the liquid brine on the micrometric fingers indicates a significant increase in the brine surface area compared to that of the flat ice surface at high temperatures, whereas the NaCl crystals can become sites of heterogeneous reactivity at lower temperatures. There is no evidence that, without external forces, salty FFs could automatically fall apart to create a number of sub-particles at the scale of micrometres as the exposed brine fingers seem cohesive and hard to break in the middle. The fingers tend to combine together to form large spheres and then join back to the mother body, eventually forming a large chunk of salt after complete dehydration. A present microscopic observation rationalizes several previously unexplained observations, namely, that FFs are not a direct source of sea salt aerosols and that saline ice crystals under evaporation could accelerate the heterogeneous reactions of bromine liberation.

Saline Growth Conditions Favour Supercooling and Increase the Freezing Tolerance of Leaves of Barley and Wheat

1992 ◽  
Vol 47 (9-10) ◽  
pp. 695-700 ◽  
Author(s):  
Michael Bender ◽  
Ulrich Heber ◽  
Karl-Josef Dietz
Keyword(s):  
Salt Stress ◽  
Freezing Tolerance ◽  
Growth Conditions ◽  
Ice Nucleation ◽  
Ice Formation ◽  
Freezing And Thawing ◽  
Subzero Temperatures ◽  
Cellular Dehydration ◽  
Detached Leaves ◽  
Leaf Survival

When young plants of barley and wheat grown in hydroponic culture were subjected to salt stress, their freezing tolerance increased with increasing severity of salt stress. Detached leaves from salt-stressed plants also exhibited an increased ability to supercool. Avoidance of ice formation permitted leaf survival at subzero temperatures which were no longer tolerated when ice nucleation resulted in extracellular freezing. The increased freezing tolerance under salt stress is attributed to osmotic adjustment of the plants. Increased cellular solute concentrations decrease the extent of cellular dehydration at freezing temperatures, thereby decreasing mechanical and chemical stresses on biomembranes during freezing and thawing.

scholarly journals Evaporating brine from frost flowers with electron microscopy and implications for atmospheric chemistry and sea-salt aerosol formation

2017 ◽  
Vol 17 (10) ◽  
pp. 6291-6303 ◽  
Author(s):  
Xin Yang ◽  
Vilém Neděla ◽  
Jiří Runštuk ◽  
Gabriela Ondrušková ◽  
Ján Krausko ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Ambient Air ◽  
Sea Salt ◽  
Heterogeneous Reactions ◽  
Environmental Scanning ◽  
Aerosol Formation ◽  
Ice Surface ◽  
Spatial Dimensions ◽  
Frost Flowers ◽  
External Forces

Abstract. An environmental scanning electron microscope (ESEM) was used for the first time to obtain well-resolved images, in both temporal and spatial dimensions, of lab-prepared frost flowers (FFs) under evaporation within the chamber temperature range from −5 to −18 °C and pressures above 500 Pa. Our scanning shows temperature-dependent NaCl speciation: the brine covering the ice was observed at all conditions, whereas the NaCl crystals were formed at temperatures below −10 °C as the brine oversaturation was achieved. Finger-like ice structures covered by the brine, with a diameter of several micrometres and length of tens to 100 µm, are exposed to the ambient air. The brine-covered fingers are highly flexible and cohesive. The exposure of the liquid brine on the micrometric fingers indicates a significant increase in the brine surface area compared to that of the flat ice surface at high temperatures; the NaCl crystals formed can become sites of heterogeneous reactivity at lower temperatures. There is no evidence that, without external forces, salty FFs could automatically fall apart to create a number of sub-particles at the scale of micrometres as the exposed brine fingers seem cohesive and hard to break in the middle. The fingers tend to combine together to form large spheres and then join back to the mother body, eventually forming a large chunk of salt after complete dehydration. The present microscopic observation rationalizes several previously unexplained observations, namely, that FFs are not a direct source of sea-salt aerosols and that saline ice crystals under evaporation could accelerate the heterogeneous reactions of bromine liberation.

scholarly journals Chemical composition of soluble and insoluble particles around the last termination preserved in the Dome C ice core, inland Antarctica

2016 ◽  
Author(s):  
Ikumi Oyabu ◽  
Yoshinori Iizuka ◽  
Eric Wolff ◽  
Margareta Hansson
Keyword(s):  
Chemical Composition ◽  
Atmospheric Chemistry ◽  
Ice Core ◽  
Ice Cores ◽  
Soluble Salt ◽  
Chemical Compositions ◽  
Insoluble Particles ◽  
Polar Ice Sheets ◽  
Sublimation Method ◽  
Ice Sublimation

Abstract. Knowing the chemical composition of particles preserved in polar ice sheets is useful for understanding past atmospheric chemistry. Recently, several studies have examined the chemical compositions of soluble salt particles preserved in ice cores from inland and peripheral regions in both Antarctica (Dome Fuji and Talos Dome) and Greenland (NEEM). On the other hand, there is no study that compares salt compositions between different sites in inland Antarctica. This study examines the chemical compositions of soluble salt particles around the last termination in the Dome C ice core, and compares them to those from Dome Fuji. Particles larger than 0.45 μm are obtained from the ice core by an ice sublimation method, and their chemical compositions are analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy. The major soluble salt particles are CaSO4, Na2SO4, and NaCl, which is the same as that from the Dome Fuji ice core. Time-series changes in the composition of these salts are similar to those for the Dome Fuji ice core. Specifically, from 25 to 18 ka, the ratio of NaCl to Na2SO4 is variable, but generally the CaSO4 and NaCl fractions are high and the Na2SO4 fraction is low. Between 18 and 17 ka, the CaSO4 and NaCl fractions decrease and the Na2SO4 fraction increases. Between 16 and 6.8 ka, the CaSO4 and NaCl fractions are low and Na2SO4 fraction is high. However, the sulfatization rate of NaCl at Dome C is higher than that at Dome Fuji. We argue that this higher rate arises because at Dome C more SO42− is available for NaCl to form Na2SO4 due to a lower concentration of Ca2+.

scholarly journals Efficiency of biocompost potentiated with chemical fertilizer and facilitated aeration

2020 ◽  
Vol 42 ◽  
pp. e31
Author(s):  
Guilherme Junqueira Jerônimo ◽  
Ana Paula Milla dos Santos Senhuk ◽  
Mário Sérgio da Luz ◽  
Julio Cesar de Souza Inácio Gonçalves ◽  
Deusmaque Carneiro Ferreira
Keyword(s):  
Seedling Growth ◽  
Food Industry ◽  
Organic Waste ◽  
Nutrient Content ◽  
Chemical Fertilizer ◽  
Natural Conditions ◽  
Stabilization Time ◽  
Lettuce Seedling

The aims were to reduce composting time, to evaluate the application of produced composts and to size two composting yards (conventional and potentiated). Eight compost heaps with 400 kg of food industry or urban organic waste were built: 1) control; 2) facilitated aeration; 3) potentiated with facilitated aeration and chemical fertilizer; and 4) chemical fertilizer. The analyzed parameters were pH, temperature, humidity and C/N ratio. Compost heap reached stabilization at 90 days without chemical fertilizer and at 25 days when potentiated, regardless of the waste origin. Stabilized composts were applied to lettuce crop under natural conditions and compared with commercial compost. Composts with chemical fertilizer were the most effective in enabling lettuce seedling growth. For medium-sized cities, the conventional composting yard requires 6.58 ha, whereas the potentiated composting yard requires 1.69 ha, considering the recorded stabilization time of 90 and 25 days, respectively. The potentiated composting was the most efficient because its shorter stabilization time, did not require manual turning and produced compost with higher nutrient content. Besides that, requires an area 74.32% smaller than the conventional yard, fact that enables using this process to treat industrial and urban solid organic waste.

scholarly journals Simulation of polar stratospheric clouds in the chemistry-climate-model EMAC via the submodel PSC

2010 ◽  
Vol 3 (4) ◽  
pp. 2071-2108 ◽  
Author(s):  
O. Kirner ◽  
R. Ruhnke ◽  
J. Buchholz-Dietsch ◽  
P. Jöckel ◽  
C. Brühl ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Growth Factor ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Surface Growth ◽  
Ice Formation ◽  
Polar Stratospheric Clouds ◽  
Ternary Solutions ◽  
Stratospheric Clouds

Abstract. The submodel PSC of the ECHAM5/MESSy Atmospheric Chemistry model (EMAC) has been developed to simulate the main types of polar stratospheric clouds (PSC). The parameterisation of the supercooled ternary solutions (STS, type 1b PSC) in the submodel is based on Carslaw et al. (1995b), the thermodynamical approach to simulate ice particles (type 2 PSC) on Marti and Mauersberger (1993). For the formation of nitric acid trihydrate (NAT) particles (type 1a PSC) two different parameterisations exist. The first one is based on an instantaneous thermodynamical approach from Hanson and Mauersberger (1988), the second one (new implemented by Kirner, 2008) considers the growth of the NAT particles with aid of a surface growth factor based on Carslaw et al. (2002). Via namelist switches the NAT parameterisation, as well as some parameters for the NAT and ice formation can be chosen. This publication explains the background of the submodel PSC and the use of the submodel with the goal to simulate realistic PSC in EMAC.

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