Deliquescence is the process whereby a solid interacts with a humid atmosphere and begins to dissolve when the partial pressure of H2O in the atmosphere exceeds the partial pressure of H2O at which the solid is in equilibrium at a given temperature. Deliquescence of sulfate minerals poses a risk to both plant and animal life as metals and acid that are stored in the mineral structure are released. Detailed solid-solution transition boundaries for sulfate minerals aid in the understanding of acid mine waste behavior in the event of environmental changes. The deliquescence behaviors of ferricopiapite, melanterite, halite and epsomite have been studied as a function of temperature and relative humidity. A device has been developed to determine the onset of deliquescence as the temperature and/or relative humidity around a sample of sulfate mineral is varied. Experiments were conducted on several synthetic analogues of minerals. Ferricopiapite was studied as it is the most likely mineral to exhibit this behavior in common acid mine drainage sites where sulfates are present. Because no experimental data exist for the deliquescence of ferricopiapite, in order to properly test the device experiments in which the relative humidity was raised above the deliquescence point and then reversed were conducted using synthetic melanterite and halite for which solid-vapor equilibrium constants for temperature and relative humidity are known. Results of the reversal experiments for melanterite and halite show that the surface resistivity probe designed for this study accurately determines the onset of deliquescence as predicted by the known solid-liquid-vapor phase diagrams. The deliquescence of copiapite is not a reversible process as it does not re-precipitate from the liquid created by deliquescence as the relative humidity is lowered. Epsomite was studied to determine if there was any crystallographic control of the onset of deliquescence between different crystal faces. A significant and consistent difference in the onset of deliquescence was observed between the {111} and {100} faces with the {111} face always being the first to deliquesce as a function of increased relative humidity. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2011-01-11 11:33:03.957

During the summer of 2002, a modified tandem differential mobility analyzer (TDMA) was used to examine the size-resolved hydration state of the ambient aerosol in Southeast Texas. Although there were slight variations in the measured properties over the course of the study, the deliquescent particles observed were almost always present as metastable aqueous solutions. A relative humidity (RH) scanning TDMA system was used to measure the deliquescence/crystallization properties of ambient aerosol populations in the same region. During August, sampling was conducted at a rural site in College Station, and in September at an urban site near the Houston ship channel. Measurements from both sites indicate cyclical changes in the composition of the soluble fraction of the aerosol, which are not strongly linked to the local aerosol source. The observations show that as temperature increases and RH decreases, the hysteresis loop describing the RH-dependence of aerosol hygroscopic growth collapses. It is proposed that this collapse is due to a decrease in the ammonium to sulfate ratio in the aerosol particles, which coincides with increasing temperature and decreasing RH. This cyclical change in aerosol acidity may influence secondary organic aerosol (SOA) production and may exaggerate the impact of the aerosol on human health. The compositional changes also result in a daily cycle in crystallization RH that is in phase with that of the ambient RH, which reduces the probability that hygroscopic particles will crystallize in the afternoon when the ambient RH is a minimum. During June and July of 2004 airborne measurements of size-resolved aerosol hygroscopic properties were made near Monterey, California. These were used to examine the change in soluble mass after the aerosol had been processed by cloud. The calculated change in soluble mass after cloud-processing ranged from 0.66 g m-3 to 1.40 g m-3. Model calculations showed these values to be within the theoretical bounds for the aerosols measured. Mass light-scattering efficiencies were calculated from both an averaged aerosol size distribution and from distributions modified to reflect the effects of cloud. These calculations show that the increase in mass light-scattering efficiency should be between 6% and 14%.

Semiconductor wafer manufacturing facilities (fab) must maintain extremely clean air environments to minimize the number of wafers scrapped due to contamination which would result in reduced yields. The fab air is cleaned bypassing it through either HEPA or ULPA filters. A number of airborne fab contaminants may be hygroscopic causing them to exist as a solid or a liquid when in equilibrium with their environment's relative humidity. The effect of relative humidity on such contaminants is poorly documented whether they were to be captured in a filter or deposited on a wafer. The work presented here experimentally characterizes NaCl evolution within HEPA filters when exposed to humidity fluctuations and the effect of humidity on NH4Cl corrosiveness when deposited on cobalt coated wafers with a TiN layer. Successive deliquescence and efflorescence fluctuations were imposed on particles captured on a glass fiber HEPA filter. Scanning Electron Microscopy (SEM) and Environmental SEM (ESEM) studies of the filters showed that the NaCl, under humidity excursions, did not penetrate deep into the filter but deliquesced and effloresced near the top surface of the filter. Pressure drop measurements for filters containing NaCl particles showed differences in pressure drop associated with relative humidity changes. These pressure drop changes suggested some redistribution particle properties. When exposed to a relative humidity of 20%, the NH4Cl particles did not corrode the cobalt wafer beyond the location of the initial deposit. At 61% relative humidity, the surrounding areas of the particles were corroded with a solid artifact left at the original location. At 76% relative humidity the NH4Cl particles were observed to have deliquesced, which is below the expected deliquescence relative humidity. The corrosion of the cobalt wafer was most extensive when the NH4Cl particles had deliquesced. / text

The goal of this project was to study the deliquescence kinetics of aerosol particles of atmospheric significance. In the course of this work a novel experimental method was developed, which utilizes the measurement of the water vapor loss in laminar aerosol flow to determine vapor uptake on the aerosol surface. The newly designed flow tube apparatus uses a system of Nafion based dryers and humidifiers, which greatly simplifies the optimization and control of the relative humidity in the aerosol flow. The design, which also utilizes a movable inlet, enables easy variation of the aerosol residence time in the deliquescence reactor, while keeping other experimental conditions constant. In this study, a numerical retrieval procedure was used to characterize aerosols in situ from their IR extinction spectra. The procedure allows that the aerosol size, number distribution, phase and composition be determined, provided the optical constants of all the components (materials) comprising the aerosol are known. For the purpose of studying the deliquescence kinetics of ammonium sulfate aerosol and monitoring their evolution from solid to liquid (state), we have acquired a set of optical constants for a range of (NH4)2SO4 compositions. A set of experiments in a somewhat modified flow tube set up was performed to produce AMS aerosols of known composition, including solid, saturated (water) solution (40 % wt.) and a series of diluted solutions with composition ranging between 40 and 10 % wt. in 5 % increments. The IR spectra of these model aerosols were used to derive the optical constants, using an inversion method proposed by Clapp. The derived refractive indices, which cover the spectral range from 590 to 5990 cm-1 with 2 cm-1 resolution, were compared with those already available in the literature. Using various examples to compare the quality of fittings to experimental spectra, we demonstrated that our optical constants present an improvement relative to those previously reported by B. Toon’s (for crystalline AMS) and S. Martin’s (for AMS solution). The suitability of applying this procedure to ammonium sulfate aerosols and its sensitivity to spectral range was also investigated and discussed. As a preparatory step for the deliquescence kinetics study, our new flow tube apparatus and the tools for the characterization of aerosol were verified in a standard deliquescence experiment performed on (NH4)2SO4 aerosols. The deliquescence process of an equilibrated aerosol flow was monitored as a function of increasing humidity and the deliquescence relative humidity (DRH) determined to be 79.6 ± 0.85 % which is, within experimental uncertainty, in an excellent agreement with the results reported by other research groups. In the kinetic experiment, a flow of solid (NH4)2SO4 aerosols is pre-humidified to a humidity close to, but enough below DRH that there is no detectable amount of liquid aerosols in the system. Such an equilibrated aerosol flow was introduced to the deliquescence reactor where it is further humidified in a controllable manner, by varying the position of the movable inlet. The amount of water transferred to the aerosol through the Nafion membrane was closely monitored, as well as the resulting increase in the water content in the aerosol flow (both gaseous and liquid). This was achieved by measuring the RHs and flow rates of the aerosol and humidification flow, and the characterization of aerosol composition and concentration using their IR spectra. The experimental conditions and aerosol residence times in the reactor where chosen such that no other diluted solution except for saturated (NH4)2SO4 droplets were produced in the process. The number distribution of deliquesced aerosols and the corresponding change in the water content in the aerosol flow were used by a newly developed kinetic model to determine the kinetics of the deliquescence process. Assuming fully developed laminar flow conditions, the water vapor concentration in the flow and its depletion in the presence of aerosol was modeled, to retrieve the value of the water vapor uptake. In the case of micron-sized ammonium sulfate aerosols, which were used in this study, the uptake coefficient,, was determined to be 0.0072 ± 6.54x10-3. The uncertainty associated with this value, as well as the suggested improvements to the experimental procedure and the kinetic model in order to reduce the uncertainty were discussed.

The goal of this project was to study the deliquescence kinetics of aerosol particles of atmospheric significance. In the course of this work a novel experimental method was developed, which utilizes the measurement of the water vapor loss in laminar aerosol flow to determine vapor uptake on the aerosol surface. The newly designed flow tube apparatus uses a system of Nafion based dryers and humidifiers, which greatly simplifies the optimization and control of the relative humidity in the aerosol flow. The design, which also utilizes a movable inlet, enables easy variation of the aerosol residence time in the deliquescence reactor, while keeping other experimental conditions constant. In this study, a numerical retrieval procedure was used to characterize aerosols in situ from their IR extinction spectra. The procedure allows that the aerosol size, number distribution, phase and composition be determined, provided the optical constants of all the components (materials) comprising the aerosol are known. For the purpose of studying the deliquescence kinetics of ammonium sulfate aerosol and monitoring their evolution from solid to liquid (state), we have acquired a set of optical constants for a range of (NH4)2SO4 compositions. A set of experiments in a somewhat modified flow tube set up was performed to produce AMS aerosols of known composition, including solid, saturated (water) solution (40 % wt.) and a series of diluted solutions with composition ranging between 40 and 10 % wt. in 5 % increments. The IR spectra of these model aerosols were used to derive the optical constants, using an inversion method proposed by Clapp. The derived refractive indices, which cover the spectral range from 590 to 5990 cm-1 with 2 cm-1 resolution, were compared with those already available in the literature. Using various examples to compare the quality of fittings to experimental spectra, we demonstrated that our optical constants present an improvement relative to those previously reported by B. Toon’s (for crystalline AMS) and S. Martin’s (for AMS solution). The suitability of applying this procedure to ammonium sulfate aerosols and its sensitivity to spectral range was also investigated and discussed. As a preparatory step for the deliquescence kinetics study, our new flow tube apparatus and the tools for the characterization of aerosol were verified in a standard deliquescence experiment performed on (NH4)2SO4 aerosols. The deliquescence process of an equilibrated aerosol flow was monitored as a function of increasing humidity and the deliquescence relative humidity (DRH) determined to be 79.6 ± 0.85 % which is, within experimental uncertainty, in an excellent agreement with the results reported by other research groups. In the kinetic experiment, a flow of solid (NH4)2SO4 aerosols is pre-humidified to a humidity close to, but enough below DRH that there is no detectable amount of liquid aerosols in the system. Such an equilibrated aerosol flow was introduced to the deliquescence reactor where it is further humidified in a controllable manner, by varying the position of the movable inlet. The amount of water transferred to the aerosol through the Nafion membrane was closely monitored, as well as the resulting increase in the water content in the aerosol flow (both gaseous and liquid). This was achieved by measuring the RHs and flow rates of the aerosol and humidification flow, and the characterization of aerosol composition and concentration using their IR spectra. The experimental conditions and aerosol residence times in the reactor where chosen such that no other diluted solution except for saturated (NH4)2SO4 droplets were produced in the process. The number distribution of deliquesced aerosols and the corresponding change in the water content in the aerosol flow were used by a newly developed kinetic model to determine the kinetics of the deliquescence process. Assuming fully developed laminar flow conditions, the water vapor concentration in the flow and its depletion in the presence of aerosol was modeled, to retrieve the value of the water vapor uptake. In the case of micron-sized ammonium sulfate aerosols, which were used in this study, the uptake coefficient,, was determined to be 0.0072 ± 6.54x10-3. The uncertainty associated with this value, as well as the suggested improvements to the experimental procedure and the kinetic model in order to reduce the uncertainty were discussed.

The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Harsh abiotic conditions of the polar desert ecosystem, including extreme cold, aridity, and limited nutrient availability select for unique taxa. The comparatively simple terrestrial ecosystem is well-suited for investigating edaphic influences on microbial presence, activity, and community structuring. The Dry Valleys are viewed as a useful analog for Mars astrobiology investigations. However, most biotic investigations have been focused on lower elevations, where an understanding of edaphic effects on microbial communities within its generally more favorable conditions has emerged. Transiently wetted Dry Valley water tracks may be analogous to recurring slope lineae on Mars. Dry permafrost is rare on Earth, and unique to high-elevation Antarctica soils, but is ubiquitous on Mars. Identifying if abiotic properties known to structure microbial communities within low elevation soils holds true for water tracks and dry permafrost is not known. My dissertation investigates edaphic effects on microbial communities within water track soils and dry permafrost. First, I review the ecological effects of transient wetting within hyperarid environments of the Atacama Desert of Chile and the Dry Valleys of Antarctica and apply the findings to possible habitability of modern and early (i.e., ~3.5 bya) Mars surface environments. I show that deliquescent hygroscopic salts facilitate biological response where little or no biotic activity would occur otherwise, yet the salts can also inhibit life. Transient wetting alone may also not be enough to support life. Secondly, I examine bacterial community composition, richness, and diversity on and off water track soils in Taylor Valley and show they are significantly different in composition, which likely influence ecosystem functioning. Salinity is shown as the best predictor of composition. Third, I examine a bacterial community from a Beacon Valley water track, which we believe is among the highest, driest, and coldest soils on Earth that still experiences brief seasonal wetting. I show a small but diverse community is present, with some viable cells, yet no detectable RNA is expressed by the community when tested within a suite of simulated Martin soils. Finally, I examine bacterial and fungal communities in dry permafrost of Arena Valley. I show a strikingly minimal microbial community severely restricted by the extreme cold, oligotrophy, and aridity. Several abundant taxa are related to those within maritime, costal, and endolithic habitats, indicating that they are foreign inoculum. The communities appear to be inactive to such a degree that they are not meaningfully structured by the broad suite of measured abiotic properties. Dry permafrost soils and water track environments are extremely challenging habitats, but they are generally more favorable than conditions observed on Mars. My research has important ecological value for investigating terrestrial thresholds of microbial habitability on Earth and for Mars astrobiology investigations.

Le mottage ou l’agglomération non désirée des cristaux déliquescents est un phénomène récurrent dans l’industrie, notamment au cours du transport et du stockage. Les variations des conditions environnantes sont fréquemment responsables de la dégradation de ce type de poudres. En particulier, les fluctuations de l’humidité ambiante conduisent à la formation d’une solution saturée par déliquescence du solide puis à la formation de ponts solides par évaporation de l’eau. Dans cette étude, on se concentre sur le chlorure de sodium. L’équilibre avec la vapeur d’eau et les cinétiques de prise et perte en eau sont analysés et reliés au comportement mécanique macroscopique des cristaux. Le contact avec des cristaux de différente nature tels que le sucrose met en évidence le phénomène de déliquescence mutuelle. Le modèle des solutions régulières appliqué aux systèmes ternaires comportant du NaCl, du sucrose et de l’eau permet de mieux comprendre la chute de déliquescence. La présence des molécules d’eau à la surface des cristaux et la condensation capillaire à faible humidité relative provoque la déliquescence de NaCl et du sucrose simultanément. L’évaporation de l’eau et la recristallisation des cristaux à partir de la solution ainsi formée sont inhibées, en particulier à la composition solide du point eutonique. Le comportement singulier à cette composition qui s’apparente à celui d’un corps pur montre une recristallisation partielle du mélange "eutonique" associée à la formation d’une phase amorphe dans les conditions de l’expérimentation. Afin d’éviter le renforcement au mottage, l’étude de différents agents anti-mottants révèle l’efficacité du stéarate de magnésium. / Caking or undesired agglomeration of deliquescent crystals is a recurrent phenomenon in industry, especially during transportation and storage. The variation of environmental conditions is often pointed out as a cause of the degradation of this kind of powders. More precisely, the fluctuations of ambient humidity lead to the formation of a saturated solution by deliquescence followed by the formation of solid bridges when water evaporates. Sodium chloride is chosen as a model substance in this study. The equilibrium with water vapor and the kinetics of water uptake and loss are analyzed and related to the mechanical macroscopic behavior of crystals. The contact with crystals of different nature such as sucrose highlights the phenomenon of mutual deliquescence. The model of regular solutions applied to ternary systems containing NaCl, sucrose and water allows a better understanding of deliquescence lowering. The presence of water molecules and capillary condensation at low relative humidity lead to the deliquescence of NaCl and sucrose simultaneously. Water evaporation and recrystallization of solid from such solution is compromised, especially at the solid composition of the “eutonic point”. The singular behavior at this composition which resembles to the one of a pure substance shows a partial recrystallization of the “eutonic” mixture and the formation of an amorphous phase under the experimental conditions applied. In order to avoid caking reinforcement, the study of differentanti-caking agents reveals the efficiency of magnesium stearate.