scholarly journals Snow physics as relevant to snow photochemistry

2007 ◽  
Vol 7 (3) ◽  
pp. 5941-6036 ◽  
Author(s):  
F. Domine ◽  
M. Albert ◽  
T. Huthwelker ◽  
H.-W. Jacobi ◽  
A. A. Kokhanovsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Quantitative Description ◽  
Field Measurements ◽  
Liquid Water Content ◽  
Reactive Gases ◽  
Snow Physics ◽  
Snow Photochemistry

Abstract. Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires the knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, optical properties, thermal conductivity, permeability and gas diffusivity. Inasmuch as possible, equations to parameterize these properties as a function of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples.

scholarly journals Snow physics as relevant to snow photochemistry

2008 ◽  
Vol 8 (2) ◽  
pp. 171-208 ◽  
Author(s):  
F. Domine ◽  
M. Albert ◽  
T. Huthwelker ◽  
H.-W. Jacobi ◽  
A. A. Kokhanovsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Quantitative Description ◽  
Field Measurements ◽  
Liquid Water Content ◽  
Reactive Gases ◽  
Snow Physics ◽  
Snow Photochemistry

Abstract. Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, thermal conductivity, permeability, gas diffusivity and optical properties. Inasmuch as possible, equations to parameterize these properties as functions of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples.

scholarly journals Simulation of the specific surface area of snow using a one-dimensional physical snowpack model: implementation and evaluation for subarctic snow in Alaska

2010 ◽  
Vol 4 (1) ◽  
pp. 35-51 ◽  
Author(s):  
H.-W. Jacobi ◽  
F. Domine ◽  
W. R. Simpson ◽  
T. A. Douglas ◽  
M. Sturm
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Winter Season ◽  
Data Set ◽  
Thermal Budget ◽  
One Dimensional ◽  
Snow Model ◽  
Physics Model ◽  
Snow Physics

Abstract. The specific surface area (SSA) of the snow constitutes a powerful parameter to quantify the exchange of matter and energy between the snow and the atmosphere. However, currently no snow physics model can simulate the SSA. Therefore, two different types of empirical parameterizations of the specific surface area (SSA) of snow are implemented into the existing one-dimensional snow physics model CROCUS. The parameterizations are either based on diagnostic equations relating the SSA to parameters like snow type and density or on prognostic equations that describe the change of SSA depending on snow age, snowpack temperature, and the temperature gradient within the snowpack. Simulations with the upgraded CROCUS model were performed for a subarctic snowpack, for which an extensive data set including SSA measurements is available at Fairbanks, Alaska for the winter season 2003/2004. While a reasonable agreement between simulated and observed SSA values is obtained using both parameterizations, the model tends to overestimate the SSA. This overestimation is more pronounced using the diagnostic equations compared to the results of the prognostic equations. Parts of the SSA deviations using both parameterizations can be attributed to differences between simulated and observed snow heights, densities, and temperatures. Therefore, further sensitivity studies regarding the thermal budget of the snowpack were performed. They revealed that reducing the thermal conductivity of the snow or increasing the turbulent fluxes at the snow surfaces leads to a slight improvement of the simulated thermal budget of the snowpack compared to the observations. However, their impact on further simulated parameters like snow height and SSA remains small. Including additional physical processes in the snow model may have the potential to advance the simulations of the thermal budget of the snowpack and, thus, the SSA simulations.

Gold Cementation by Dendritic Zinc Powders in Percolation Mode

2020 ◽  
Vol 989 ◽  
pp. 543-547
Author(s):  
K.D. Naumov ◽  
Vladimir G. Lobanov
Keyword(s):  
Particle Size ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Specific Surface Area ◽  
Alkaline Solutions ◽  
Wide Range ◽  
Zinc Powders ◽  
Cyanide Solutions

In present article gold cementation features from cyanide solutions using dendritic zinc powders are studied. The powders were obtained by electroextraction from alkaline solutions. Powders with different physical properties were obtained by means of change in current density (from 0.5 to 2 A/m2) and NaOH concentration in solution (from 100 to 400 g/dm3) at the constant zinc concentration (10 g/dm3). The physical properties of mentioned powders were studied using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS). It is shown that electrolytic powders have high specific surface area, which is 1.8–2.6 times larger than the surface area of ​​the zinc powder currently used for cementation. At that electrolytic powders particle size is 8-22 times larger than the particle size of powder currently used for cementation. The reason of high specific surface area is the electrolytic zinc powders dendritic structure. It was found that the obtained powders precipitate gold from cyanide solutions with a greater efficiency in a wide range of productivity. Laboratory unit simulating Merrill-Crow technology was used for cementation. Immediately ahead conducting the experiments, Na2SO3 was added to the solution in excess to remove dissolved oxygen. Zinc powders were plated by dendritic lead before loading into the laboratory setup by cementation. Lead was added as acetate (Pb (CH3COO)2). The consumption of lead acetate was 10% by weight of zinc. Correlation between the powders physical properties and the gold extraction is shown.

scholarly journals Mixture Design Approach on the Physical Properties of Lignin-Resorcinol-Formaldehyde Xerogels

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Chris D. Castro ◽  
Germán C. Quintana
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Bulk Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
Black Liquor ◽  
Adsorptive Capacity ◽  
Gel Formation ◽  
Soda Pulping ◽  
Catalyst Content

Organic xerogels were functionalized by incorporating sugarcane bagasse lignin from soda pulping black liquor, not used so far in this materials, with the aim of introducing new functional groups on traditional gels that could improve its adsorptive capacity. Two mixing designs were applied to identify the reactive combinations that allow a well gel formation and to adjust models that predict physical properties. The designs study five components: resorcinol (R, 0.04–0.3), lignin (L, 0.004–0.14), formaldehyde (F, 0.08–0.17), water (W, 0.45–0.8), and NaOH (C, 0.0003–0.0035). The first experimental design was an extreme vertices design and its results showed shrinkage between 4.3 and 59.7 and a bulk density from 0.54 to 1.3; a mass ratioLR/Fnear 1.5 was required for gel formation. In the second design a D-Optimal was used to achieve better adjusted coefficients and incorporate the largest possible amount of lignin in the gels. Bulk density varies from 0.42 to 0.9, shrinkage varies from 3.42 to 25.35, and specific surface area reaches values of 451.86 m2/g with 13% lignin and 270 m2/g with 27% lignin. High catalyst content improves lignin dissolution and increase shrinkage and bulk density of xerogels and bulk density. Lignin contributes to reducing shrinkage and specific surface area due to his compact and rigid structure.

scholarly journals Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

Nanoscale ◽  
2021 ◽  
Author(s):  
Wendong Zhu ◽  
Ya Cheng ◽  
Ce Wang ◽  
Nicola Pinna ◽  
Xiaofeng Lu
Keyword(s):  
Transition Metal ◽  
Mass Transport ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Metal Sulfides ◽  
Large Specific Surface Area ◽  
One Dimensional ◽  
Significant Attention

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport,...

scholarly journals Impact of Agromeliorative Measures on the Specific Surface of Soil

2020 ◽  
Vol 6 (10) ◽  
pp. 135-142
Author(s):  
S. Gurbanov
Keyword(s):  
Soil Fertility ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sandy Soil ◽  
Colloidal Particles ◽  
Soil Layer ◽  
First Year ◽  
Special Surface

The article is devoted to the study of the regularity of changes in the specific surface of soil under the influence of agromeliorative measures, mainly irrigation and agrotechnical works carried out in the gray-brown soils of the Absheron Peninsula of Azerbaijan. Based on four years of experiments, it was determined that changes occur in the specific surface of the soil in the plowed layer as a result of the agromeliorative measures taken. Thus, a decrease in the specific surface area was observed in the 0–20 cm soil layer, and an increase in the specific surface area was observed in the 20–40 cm soil layer. In the first year of the experiments, the value of the average specific surface in the 0–20 cm soil layer was 3,098–3,988 cm2/g, and in the 20–40 cm soil layer it was 1,056–3,567 cm2 /g. However, after four years, the value of the special surface was 1,949–3,340 cm2/g in the 0–20 cm soil layer and 3,290–5,023 cm2/g in the 20–40 cm layer. The increase in the specific surface area in the lower layers of the soil is due to the gradual washing of dust, silt and colloidal particles from the plow layer to the lower layers. The reduction of the specific surface in the topsoil leads to the degradation of the topsoil, the deterioration of the water-physical properties, the formation of compaction below the topsoil, and ultimately the reduction of soil fertility. The article makes specific suggestions to prevent this process. It was also identified based on the calculations that the specific surface area of the soil, rich in silt, dust and colloidal particles, is many times larger than the specific surface area of sandy soil. The specific surface area of colloidal silt is 43,000 times larger than the specific surface area of dust and 130,000 times larger than the specific surface area of sand.

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