Transport in snow

WATER-VAPOR TRANSPORT IN SNOW WITH HIGH TEMPERATURE GRADIENT... 

Several studies have investigated empirically the flux of chemicals within snow or between snow and the atmosphere (Guimbaud et al., 2002 Albert and Shultz, 2002 Herbert et al., 2006). In particular, measured concentration gradients within the atmospheric boundary layer or within the snow pack have been used to calculate a chemical s flux into or out of the snow pack. This approach has resulted in miscellaneous parameterizations to calculate fluxes of, for example, carbonyl compounds and NO c species from the snow pack as a result of photochemical processes in snow (Domind and Shepson, 2002 Hutterli et al., 1999 Guimbaud et al., 2002 Grannas et al., 2002). However, flux measurements can only be used to derive kinetic transport parameters, such as diffusivities and mass transport coefficients, if the chemicals involved are reasonably persistent and do not undergo rapid conversions within the snow pack. For example, measurements of the flux of carbonyl compounds out of snow are more likely to reflect the kinetics of formation in the snow pack than the kinetics of snow-air gas exchange. As a result, there is a very limited number of experimental studies that provide quantitative information on the rate of chemical transport in snow. 

A similar calculation using measurements of physical snow properties and interstitial ozone concentrations further confirmed the significance of surface roughness features for a chemical s transport in snow (Albert et al., 2002). Beneath moderate winds (t/io = 7-9ms ), surface roughness amplitudes of 10cm and roughness wavelengths of 10-20m almost the entire approximately 40 cm deep snow pack was subject to ventilation. 

Erel Y., Patterson C. C., Scott M. J., and Morgan J. J. (1990) Transport of industrial lead in snow through soil to stream water and groundwater. Chem. Geol. 85, 383-392. 

Next, the distribution of temperature and temperature gradient of the quasi steady state is depicted in Figure 3. The snow sample was initially kept at -10 °C, and was cooled from the top cooling plate to -65 °C, reaching a quasi steady state in about 6 hours. The temperature distribution showed upward convex curve. Therefore, the temperature gradient was not uniform in the sample. This tendency is same as a typical temperature profile in subarctic snow. In addition, the nonlinearity of the snow temperature distribution resulted from water vapor transport in the snow. ... 

The water vapor flux seems to affect significantly the growth rate of depth hoar snow. It seemed that water vapor transportation also caused a density change in snow. The initial and final density of each layer is illustrated in Figure 6. Before and after the experiment, the lost mass was only 0.5 %. The density of layer I (warmest) decreased. 

Snow, V.O., B.E. Clothier, D.R. Scotter, and R.E. White. 1994. Solute transport in a layered field soil experiments and modelling using the convection-dispersion approach. J. Contamin. Hydrol. 

Laboratory studies have shown that mineral spirits are sorbed by fresh snow with a mean sorption ratio of 1.5 g mineral spirits/g snow. This would indicate that if a spill occurred on a snow- covered site, not only would sorption to soil be decreased if the ground were frozen, but drainage from the site would be decreased due to snow sorption (Martel and Nadeau 1994). When the snow melted, the solvent would be expected to be transported in the same way as the melted snow. 

Dry chlorine, in either the gaseous or liquid state, can be handled satisfactorily in carbon steel containers/cylinders. The dry chlorine is transported in cylinders up to 75 kg capacity or in one-ton containers. All containers, whether empty or full, must be stored in a dry area and protected from external heat sources such as steam pipes. If stored outdoors, they must be protected from direct sunlight, rain and snow. Chlorine containers should be segregate from other compressed gas containers. Containers must never be stored near anhydrous ammonia, hydrocarbons or flammable materials. The storage area must be well ventilated and underground storage must be avoided. 

The analysis of anions and cations in snow and ice core samples [18-21], as well as in other weakly contaminated matrices such as rain water [22], groundwater, and swimming pool water, is equally simple. The very low electrolyte content in snow and ice core samples sometimes requires the injection of large sample volumes (200 pL). Special caution is necessary during sampling. To avoid contamination during the transport between the sampling location and the laboratory, it is recommended that the samples be kept in... 

CO2 pellets are available in various sizes, but the optimum diameter for this purpose is 3 mm. They are produced in pellehsers, which press CO2 snow through a matrix to form the pellets. These are then transported in insulated boxes, or on-site production is also possible. In the liquid blasting method, CO2 liquid is drawn from an insulated tank and supplied via pipeline to a so-called gun. This consists of a dedicated chamber producing the snow and a special nozzle directing it at the target. 

The surface snow temperature of this system is targeted at —2°C. The dew temperature is defined as the temperature below which water in air condenses. If the temperature of the air that is in contact with the snow falls below the dew temperature of the air, moisture transport from the air to the snow surfacer is in the form of condensation or frosting. If the temperature of the air is above the dew temperature, the moisture transport from snow to air in the form of sublimation takes plaee. For snow with polymer, the fiiction coefficient becomes large if sublimation proceeds as a consequence of the increased polymer content on the snow particle surface. Thus, it has an adverse effect on the sliding phenomenon. The dynamic friction coefficient will be discussed later. Conversely, if too much frost develops, the snow surface will harden. The surface also will melt due to the thermal insulation of the frost. When it freezes again, it turns into ice. The energy necessary to freeze the moisture in air into frost increases the load on the cooling equipment. 

Albert and Shultz (2(X)2) used the stable and inert trace gas sulfur hexafluoride (SFe) to study both diffusive and advective transport in Arctic snow at Summit, Greenland. Chemical diffusivity in wind-packed surface snow was determined by measuring the rate of disappearance of SFe from the headspace of a steel cylinder inserted into the snow pack. Wind pack is high-density snow and consists of small rounded crystals, generated by strong and cold winds (Domind et al., 2008). The effective diffusivity was 0.06 cm s . The reduction of the molecular diffusivity by the presence of the snow pack was well described by Equation 18.12 and the empirically derived exponent n was close to the theoretically expected value of 1.5. 

Transport velocities in snow due to wind ventilation, as in Equation 18.13, were determined by injecting SFe into a 15 cm deep hoar layer beneath a dense wind pack in a snow pack with little surface roughness. The arrival of the SFe pulse 1 m upwind and 1 m downwind of the injection point was measured as a function of time (Albert and Shultz, 2002). At lower wind speeds (f/io = 3 m s ) arrival at upwind and downwind... 

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