Linear model estimates of potential salt rejection and theoretical salinity increase in a standardized water column of recurrent Arctic flaw leads and polynyas

A primitive linear model is applied to quantify potential salt rejection and theoretical salinity increase in the standardized water column of 46 individual circum-Arctic flaw leads/polynyas based on intermediate salinities, seasonal ice production rates, and flaw lead/polynya size. Analysis shows that open water with low initial salinity may not reject enough salt to produce enhanced salinities despite high ice formation rates. Conversely, flaw leads/polynyas with higher initial salinities in combination with moderate to high ice formation rates produce sufficient salt to increase flaw lead/polynya salinities. Flaw leads/polynyas with maximum potential for theoretical salinity increase and dense brine formation are located along the Beaufort Sea coast, where both initial salinities and ice formation rates are high. Salinity increase is generally moderate to high in Chukchi Sea flaw leads/polynyas, and widely moderate in the East Siberian, Kara, and Barents Seas. Southern central and southeastern Laptev Sea flaw leads/polynyas show weak potentials for salt rejection, theoretical salinity increase and dense brine formation due to extremely low salinities and ice formation rates. Though the formation of dense brines on Arctic shelves is a complex process in nature, the simplified model provides a suitable and quick (graphic) tool for Arctic marine geologists and biologists or cold region engineers to compare individual flaw lead/polynya sections in terms of freeze-related potential salt rejection and theoretical salinity increase.     

Detection of differences in sea ice crystal structure using cross-borehole DC resistivity tomography

Cross-borehole DC resistivity tomography measurements on first-year Antarctic sea ice show a decrease in the horizontal component of resistivity below 0.8 m in depth which is not related to changes in either temperature or brine volume fraction. Microstructural models derived from the resistivity data suggest that this change is related to an increased degree of horizontal connectivity in the brine microstructure of the ice. Comparison of the resistivity data with crystallographic measurements shows that this correlates with a change in ice structure from columnar ice to ice which contains an increasing fraction of platelet ice. It is thus demonstrated that not only can resistivity measurements track the temporal evolution of sea ice microstructure due to changes in temperature, but are also able to distinguish different ice types. This suggests that the dependence of sea ice properties on the distribution of brine inclusions can be studied in-situ through the use of resistivity measurements, providing a non-destructive technique for examining permeability–porosity relations in sea ice.     

Spectroscopic measurement of the vapour pressure of ice

We present a laser absorption technique to measure the saturation vapour pressure of hexagonal ice. This method is referenced to the triple-point state of water and uses frequency-stabilized cavity ring-down spectroscopy to probe four rotation-vibration transitions of at wavenumbers near 7180?cm(-1). Laser measurements are made at the output of a temperature-regulated standard humidity generator, which contains ice. The dynamic range of the technique is extended by measuring the relative intensities of three weak/strong transition pairs at fixed ice temperature and humidity concentration. Our results agree with a widely used thermodynamically derived ice vapour pressure correlation over the temperature range 0°C to -70°C to within 0.35 per cent.     

A physical model for predicting the thermal conductivity of brine-wetted snow

Recent measurements by Crocker (1984) have shown that the snowcover overlying young sea ice contains large quantities of salt (concentrations as high as 100 ppt). The influence of the salt, which is incorporated into the snowpack in the form of brine, on the thermal conductivity of the snow is analysed using a modified form of the physical thermal conductivity model developed by Pitman and Zuckerman (1967). The new model indicates that at snow densities commonly encountered in young sea ice, the presence of the brine increases the thermal conductivity of the snow by up to 50%. When the thermal conductivities predicted by the model are input into an ice-growth model, better association between observed and predicted ice growth (on Resolute Passage, North West Territories, 1982) is obtained than with any of the empirical thermal conductivity formulae tested.     

Temperature influence on light absorption by fresh water and seawater in the visible and near-infrared spectrum

The influence of temperature on light transmission in the spectral range from 400 to 760 nm has been determined in a two-cell instrument constructed especially for this purpose. Light transmission was measured over a 1-m path length in both a photometric and a spectral mode in double-ion-exchanged fresh water and filtered seawater with a salinity of approximately 25%?. For both groups of samples the temperature-dependence coefficient of the absorption was found to be -0.00091 ± 0.00006 m(-1) K(-1) in the range from 400 to 550 nm, in contrast to earlier findings. Reproducible signals could be observed only when the samples were left undisturbed for long periods of time between shifts in temperature. The temperature was scanned in alternating directions between 6 and 30 °C in steps of ± 2 °C. The time for recording a set of data was between 2 and 3 weeks. Finally, the temperature dependences of the absorption spectra were recorded in the range 400 to 760 nm. These measurements are only partially in agreement with earlier measurements.     

Icy wave-cloud lunar corona and cirrus iridescence

Dual-polarization lidar data and radiosonde data are used to determine that iridescence in cirrus and a lunar corona in a thin wave cloud were caused by tiny ice crystals, not droplets of liquid water. The size of the corona diffraction rings recorded in photographs is used to estimate the mean diameter of the diffracting particles to be 14.6 μm, much smaller than conventional ice crystals. The iridescent cloud was located at the tropopause [~11-13.6 km above mean sea level (ASL)] with temperature near -70 °C, while the more optically pure corona was located at approximately 9.5 km ASL with temperature nearing -60 °C. Lidar cross-polarization ratios of 0.5 and 0.4 confirm that ice formed both the iridescence and the corona, respectively.     

Pulse amperometric detection of salt concentrations by flow injection analysis using ionodes

A sensitive novel approach of using an amperometric ion detector for the flow injection analysis of salts has been developed. The detection methodology is based on measuring the current associated with the transfer of ions across polarized microinterfaces between the aqueous sample solution and a 2-nitrophenyloctyl ether-poly(vinyl chloride) gel phase, referred to as ionodes. Different sodium salts of fluoride, chloride, bromide, nitrate, and sulfate were investigated. It was found that by employing an amperometric pulse detection mode and pure water as eluent, the detection limit of the ionode detector could be lowered to ppt level of salt concentrations under flowing conditions.     

Nanocrystallinity in RuO2 coatings—Influence of precursor and preparation temperature

The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy, X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 °C.     

Electromagnetic properties of sea ice

Investigations of the in situ complex dielectric constant of sea ice were made using time-domain spectroscopy. It was found that (1) for sea ice with a preferred horizontal crystal c-axis alignment, the anisotropy or polarizing properties of the ice increased with depth, (2) brine inclusion conductivity increased with decreasing temperature down to about ?8°C, at which point the conductivity decreased with decreasing temperature, (3) the DC conductivity of sea ice increased with increasing brine volume, (4) the real part of the complex dielectric constant is strongly dependent upon brine volume but less dependent upon the brine inclusion orientation, (5) the imaginary part of the complex dielectric constant was strongly dependent upon brine inclusion orientation but much less dependent upon brine volume. Because the electromagnetic (EM) properties of sea ice are dependent upon the physical state of the ice, which is continually changing, it appears that only trends in the relationships between the EM properties of natural sea ice and its brine volume and brine inclusion microstructure can be established.     

The thermal conductivity of commercial brines and seawater in the freezing rangeLa conductivité thermique des saumures du commerce et de l'eau de mer en régime de congélation

This study refers to the thermal conductivity of the slush formed by NaCl and CaCl₂ brines and seawater between their freezing and eutectic temperatures. Based on equations of state relating freezing temperature and salinity, the variation of density and conductivity of the liquid brines between 0°C and their freezing points is shown on diagrams for various parameters of salinity. Their conductivity and that of ice at the respective low temperatures are introduced into a modified Maxwell-Eucken equation for calculating the conductivity of the slush. The results are given in diagrams and in empirical equations.     

Surface tension of low-temperature aqueous solutions

Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.     

Laboratory measurements of spectral reflection from ice clouds of various habits

Spectral light from 550 to 650 nm reflected from the surface of an ice cloud produced in a temperature-controlled column is measured at seven different angles between 16.7 degrees and 29.9 degrees . Cloud optical depth (tau) is determined from the extinction of a 670 nm laser and is corrected for forward scattering using a Monte Carlo ray-tracing algorithm. Reflection measurements are compared to expectations from a plane-parallel radiative transfer model with input parameters based on the measured tau and a phase function for the observed ice crystal types. The plane-parallel radiative transfer model can be used to interpret the measured reflection for tau less than about 0.4 for this particular experiment, ideal for providing a validation data set to assist with the development of satellite bidirectional remote sensing.     

Autocompensating interferometer for measuring the changes in refractive index of supercooled water as a function of temperature at 632.8 nm

An interferometric arrangement that automatically compensates for thermal expansion was used to examine the changes in the refractive index of liquid water at 632.8 nm as a function of temperature from 10 to -15 degrees C. By combining the results of this research with existing data, we calculated the absolute refractive index in the supercooled region with an accuracy ranging from 3 x 10(-6) to 1 x 10(-6). A direct observation of the refractive-index maximum of water is reported for the first time to our knowledge and found to occur between 0 and 0.1 degrees C.     

Properties of shear horizontal acoustic plate modes in BT-cut quartz

Properties of shear horizontal acoustic plate modes (SHAPMs) in BT-cut quartz were calculated and measured. A delay line with a long interdigital transducer, deposited on -50.5°YX90°-oriented quartz plate, was used for the measurements. For one of the SHAPMs, at a frequency of about 100.4 MHz, insertion loss, turnover temperature, and quadratic temperature coefficient of frequency of about 10 dB, 15°C, and -30 ppb/(°C)(2) in air, respectively, were obtained. Using water and glycerin solutions, insertion loss changes against dynamic viscosity were measured for this mode. In a viscosity range from about 1 mPa·s to 1000 mPa·s, an insertion loss change of about 14 dB was obtained.     

Buffer loading for counteracting metal salt-induced signal suppression in electrospray ionization

The decrease in the sensitivity of electrospray ionization mass spectrometry caused by the presence of metal salts, such as sodium chloride, in the sample matrix is well known and is particularly problematic for biological samples. We report here that addition of high levels of ammonium acetate can improve analyte signal in aqueous electrospray solutions and counteracts the signal suppression caused by sodium chloride. A approximately 3-fold improvement in S/N is obtained by adding 8 M ammonium acetate to aqueous solutions of cytochrome c without added sodium chloride. No organic solvents or acids are added into the electrospray solutions. The signal-to-noise ratios of cytochrome c and ubiquitin (10(-)(5) M) ions formed from aqueous solutions containing 2.0 x 10(-)(2) M sodium chloride are improved by factors of approximately 7 and 11, respectively, by adding 7 M ammonium acetate to the solution. We propose that this effect is a result of the precipitation of Na(+) and Cl(-) from solution within the evaporating electrospray droplets prior to the formation of gas-phase protein ions. This method is potentially useful for improving the abundance of protein ions formed from solutions in which the molecules have a nativelike conformation and is particularly advantageous for such solutions that have high levels of sodium.     

Studies in the setting of polyelectrolyte materials

The setting behaviour and compressive strengths of zinc polycarboxylate and glass polyalkenoate dental cements activated with sodium chloride solutions of different concentrations and also with artificial saliva have been studied. The results show that the effect of sodium chloride in these cements is concentration dependent. Saturated brine so increased the speed of set of the zinc polycarboxylate that the cement became impossible to mix. Conversely, while having little effect on the speed of setting of the glass polyalkenoate, saturated brine caused the compressive strength to fall to 18 MPa (from 85 MPa with pure water). Neither of the low-concentration solutions (i.e. 0.154 m NaCl or artificial saliva) showed any significant effects on the strength of either cement but both were found to speed up the rate of the setting reaction slightly and to sharpen the set. This effect was too slight to be a source of serious practical concern when these materials are used in clinical dentistry.     

Electrochemical oxidation of stabilized landfill leachate on DSA electrodes

The electrochemical oxidation of stabilized landfill leachate with 2960 mg L(-1) chemical oxygen demand (COD) over a Ti/IrO(2)-RuO(2) anode was investigated in the presence of HClO(4) as the supporting electrolyte. Emphasis was given on the effect of electrolysis time (up to 240 min) and temperature (30, 60 and 80°C), current density (8, 16 and 32 mA cm(-2)), initial effluent's pH (0.25, 3, 5 and 6), HClO(4) concentration (0.25 and 1M) and the addition of NaCl (20 and 100mM) or Na(2)SO(4) (20mM) as source of extra electrogenerated oxidants on performance; the latter was evaluated regarding COD, total carbon (TC), total phenols (TPh) and color removal. Moreover, the anode was studied by scanning electron microscopy and cyclic voltammetry. The main parameters affecting the process were the effluent's pH and the addition of salts. Treatment for 240 min at 32 mA cm(-2) current density, 80°C and the pH adjusted from its inherent value of 0.25 (i.e. after the addition of HClO(4)) to 3 yielded 90% COD, 65% TC and complete color and TPh removal at an electricity consumption of 35 kWh kg(-1) COD removed. Comparable performance (i.e. 75% COD reduction) could be achieved without pH adjustment but with the addition of 100mM NaCl consuming 20 kWh kg(-1) COD removed.     

Laser-induced breakdown spectroscopy for on-line engine equivalence ratio measurements

Laser-induced breakdown spectroscopy (LIBS) has been used to measure the equivalence ratio of a spark-ignited engine in a laboratory setting. Spectral features of C (711.3 nm), O (776.6 nm), N (746.3 and 743.8 nm), and CN (broad emission 707-734 nm) were used to quantify the equivalence ratio over a range from phi = 0.8 to phi = 1.2. The C/N and C/O peak ratios were found to be successful measurement metrics, compared with a standard exhaust gas oxygen analyzer, for averaged measurements. Some variation in the measurements was observed as a function of engine load. Single-shot data based on a CN/air peak ratio were evaluated using a separate calibration from averaged measurements, and the average of the single-shot data was found to agree well with the exhaust gas oxygen analyzer. The scatter in the single-shot data was substantially higher at lower equivalence ratios. The measurements including the CN peak were slightly sensitive to load, possibly due to pressure changes in the sample as the load increases, or possibly due to changes in the particle size distribution in the gas stream.     

Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals

Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO(3) structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh(3 + ); however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm; however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H(2) production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.     

Effect of corrosion-inhibitor-added deicing salts and salt substitutes on reinforcing steels: II. Influence of temperature and oxygen content

The effect of corrosion-inhibitor-added deicing salts and salt substitutes on reinforcing steels (rebars) was investigated at various temperatures and oxygen contents using galvanic cells and optical microscopy. Temperatures and oxygen contents were varied by applying stirring, oxygen-bubbling, high temperature, freeze-thaw cycle, and dry-wet cycle conditions to simulated concrete solutions mixed with 6% corrosion-inhibitor-added deicing salts, salt substitutes, and plain sodium chloride. Corrosion of reinforcing steel varied with oxygen contents and temperatures of the corrosion-inhibitor-added deicing salt and salt substitute solutions. The reinforcing steels under the freeze-thaw cycle condition showed the least corrosion, whereas those under the dry-wet cycle condition showed the most severe corrosion. The effectiveness of corrosion-inhibitor-added deicing salts and salt substitutes was found to vary with temperatures and dissolved oxygen contents.