Concentrated solar power systems are expected to be sited in desert locations where the direct normal irradiation is above 1800 kWh/m2.year. These systems include large solar collector assemblies, which account for a significant share of the investment cost. Solarreflectors are the main components of these solar collector assemblies and dust/sand storms may affect their reflectance properties, either by soiling or by surface abrasion. While soiling can be reverted by cleaning, surface abrasion is a non reversible degradation.The aim of this project was to study the accelerated aging of second surface silvered thickglass solar reflectors under simulated sandstorm conditions and develop a multi-parametric model which relates the specular reflectance loss to dust/sand storm parameters: wind velocity, dust concentration and time of exposure. This project focused on the degradation caused by surface abrasion.Sandstorm conditions were simulated in a prototype environmental test chamber. Material samples (6cm x 6cm) were exposed to Arizona coarse test dust. The dust stream impactedthese material samples at a perpendicular angle. Both wind velocity and dust concentrationwere maintained at a stable level for each accelerated aging test. The total exposure time in the test chamber was limited to 1 hour. Each accelerated aging test was interrupted every 4 minutes to measure the specular reflectance of the material sample after cleaning.The accelerated aging test campaign had to be aborted prematurely due to a contamination of the dust concentration sensor. A robust multi-parametric degradation model could thus not be derived. The experimental data showed that the specular reflectance loss decreasedeither linearly or exponentially with exposure time, so that a degradation rate could be defined as a single modeling parameter. A correlation should be derived to relate this degradation rate to control parameters such as wind velocity and dust/sand concentration.The sandstorm chamber design would have to be updated before performing further accelerated aging test campaigns. The design upgrade should improve both the reliability of the test equipment and the repeatability of accelerated aging tests. An outdoor exposure test campaign should be launched in deserts to learn more about the intensity, frequencyand duration of dust/sand storms. This campaign would also serve to correlate the results of outdoor exposure tests with accelerated exposure tests in order to develop a robust service lifetime prediction model for different types of solar reflector materials.

ABSTRACT In this study, we conducted an intensive sampling of Asian dusts at Pescadores Islands for heavy Asian continental sandstorms (ACS) from February 22 to March 6, 2008. To investigate the succession of anthropogenic and natural pollutants for the ACS transportation, PM2.5 and PM2.5-10 were sampled by two dichotomous samplers once every four hours during the ACS periods, and furthermore analyzed their physicochemical properties, including mass concentrations, particle size distribution, water-soluble ionic species, carbonaceous contents, and metallic contents. Experimental results indicated that it was mainly fine particles (PM2.5) prior to the ACS, and the percentage of anthropogenic species (i.e., SO42-, NH4+, NO3-, Zn, Mn and OC) increased dramatically. However, it changed to coarse particles while the ACS overwhelming, and the percentage of crustal/marine species (i.e., Cl-, Na+, Ca2+, Mg2+, Ca, Al, Mg and EC) increased. After the ACS, the concentrations of all species decreased substantially. However, the percentage of Cl- and Na+ increased, suggesting that sea breeze has constant influences on local suspended particles. In addition to the analysis of physicochemical properties of Asian dusts, this study applied a HYSPLIT MODEL to figure out the transportation routes and the source regions of the ACS. Backward trajectory analysis showed that the ACS was originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land. Moreover, seventeen soil samples were collected from the Tengger Desert, the Mu Us Desert, the Onqin Daga Sandy Land, and the Horqin Sandy Land in Inner Mongolia during the year of 2005. The soil samples were resuspended in a resuspension chamber and then collected by a dichotomous sampler. This study focused on PM2.5-10 particles that mainly influence the downwind regions, and then took the ACS samples and the resuspended soil samples to measure the Sr isotopic characteristics of 87Sr/86Sr ratios by a multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). To characterize the isotopic properties of resuspended dust particles from the ACS source regions in northern China, and to correlate Asian dusts at the downwind regions of ACS with the source regions by Duncan¡¦s Multiple Range Test (DMR). The DMR results showed that the ACS was probably originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land, which concurred with the backward trajectory analysis.

<p> Examination of subsurface cores of the Middle-Lower Silurian Thorold Sandstone from Consumers' Gas Silver Creek 004 Grimsby Pool indicate the presence of a single laminated sandstone facies deposited in a lower shoreface environment. Subsurface thin sections show greater development of quartz cement in the form of quartz overgrowths when compared to thin sections from surface outcrop leading to a porosity decrease of 20%. Petrographic and cathodoluminescence studies reveal that concavo-convex and sutured grain contacts, responsible for 80% of the grain contacts within the Thorold Sandstone, are generally between authigenic overgrowths and not detrital grains indicating that pressure solution is not the major source of silica within the Thorold Sandstone. Studies of detrital and authigenic clays utilizing a combination of thin section, scanning electron microscope and X-ray diffraction techniques show that illite (both detrital and authigenic) is the dominant clay mineral within the Thorold Sandstone in the 004 Pool, followed by approximately one half as much detrital kaolinite and minor authigenic chlorite. Shallow maximum depth of burial ( 786 to 1160m) and low diagenetic temperatures (30°c) suggest that clay minerals are unlikely to have undergone extensive diagenetic transformation. Consequently, detrital minerals represent the clay minerals present at the time of deposition while authigenic clays form by direct precipitation from pore fluids. During eodiagenesis mechanical compaction has reduced sandstone porosity from 40% to 28 to 29% while during mesodiagenesis the progressive paragenetic assemblage of authigenic quartz overgrowths, authigenic chlorite and authigenic illite have reduced porosity to its present value of 4 to 10%.</p> / Thesis / Bachelor of Science (BSc)

Les milieux oligotrophes sont pauvres en éléments nutritifs. En utilisant la technologie de séquençage à haut débit, on a étudié la diversité bactérienne dans trois environnements oligotrophes différents, y compris A. sâbles du désert, B. sâbles dans les tempêtes de l'Asie et C. l’eau et biofilms dans les réseaux de distribution d'eau potable.A. Le désert représente 30% de la surface de la terre. Les conditions de vie dans ces environnements sont un réel défi pour les micro-organismes à cause de nombreux facteurs limitants : peu d’eau et/ou de carbone disponible, une variation importante de température et une forte exposition aux irradiations UV. Le but de cette recherche est donc d’étudier la diversité bactérienne à la surface du sable du désert Taklemaken et du désert de Gobi en utilisant la technologie de séquençage à haut débit. Nos résultats ont révélé une grande diversité bactérienne dans le sol du désert comparable à d'autres types de sols. En outre, nous avons observé une corrélation positive entre la richesse bactérienne et le rapport C/N du sol.B. Les tempêtes de sable d'Asie se produisent presque toujours au printemps, elles sont générées dans les régions arides d'Asie telles que le désert Taklamaken et le désert de Gobi. L'arrivée des tempêtes de sable pourrait largement modifier l'environnement de l'air dans ces régions sous l’effet du vent, surtout dans les villes asiatiques qui sont le plus souvent touchées. Nos travaux visent à étudier la modification de la composition et la diversité des bactéries associées aux particules au moment de tempête de sable en Asie par la technologie de séquençage à haut débit. Nos résultats ont démontré que les compositions des bactéries associées aux particules sont modifiées pendant les tempêtes, en particulier, la proportion des Proteobacteria qui augmentent les jours de tempête. Nous avons signalé neuf genres bactériens détectés en plus pendant les jours de tempêtes, cela nécessite des études plus approfondies.C. Après avoir analysé la population bactérienne dans les tempêtes de sable, et celles des déserts, nous poursuivons notre objectif de recherche à un environnement aquatique. Nous avons suivi le flux d'eau provenant de l'usine d'Orly (DW-A) à l'entrée du réservoir (DW-B), et à la sortie du réservoir (DW-C). Nous avons constaté une forte variation de la communauté bactérienne, dans DW-A et DW-B, les bactéries prédominantes appartiennent aux populations des Betaproteobacteria, puis nous avons observé une conversion vers la population de Alphaproteobacteria dans DW-C. Le DW-C a montré une forte similitude avec un échantillon de biofilm (BF-C), ce qui suggère l'effet important du biofilm sur la modification des communautés bactériennes dans l'eau lors de la distribution. / Oligotrophic ecosystems can be loosely defined as environments that exhibit low ambient nutrient levels. During my thesis, I used 454 DNA pyrosequencing of partial 16S rDNA to explore the bacterial diversity in three different oligotrophic environments, including A. surface desert soil, B. Asian sandstorm dust and C. a section of the city of Paris’s drinking water distribution system.A. Arid regions represent nearly 30% of the Earth’s terrestrial surface. The living conditions at the surface of deserts are a challenge for microorganisms, as there is little available water and/or carbon, a very large range of temperatures and high exposure to UV irradiation from the Sun. In surface sand samples from two large Asian deserts, unexpectedly large bacterial diversity residing was revealed. Sequences belonging to the Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria phyla were the most abundant. An increase in phylotype numbers with increasing C/N ratio was noted, suggesting a possible role in the bacterial richness of these desert sand environments.B. Desert sandstorms are a meteorological phenomenon which have been postulated affect the Earth's climate and public health. We examined the particle-associated (dust and sand-associated) bacterial populations of atmospheric sand in the absence (as control) and presence of sandstorms in five Asian cities. Greater than 90% of the sequences can be classified as representing bacteria belonging to four phyla: Proteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. Principal component analyses showed that the sandstorm-associated bacterial populations were clustered by sampling year, rather than location. Members belonging to nine bacterial genera (Massilia, Planococcus, Carnobacterium, Planomicrobium, Pontibacter, Pedobacter, Lysobacter, Sanguibacter, Ohtaekwangia) were observed to increase in sand-associated samples from sandstorms, versus the controls. C. We characterized the bacterial communities in three water and three biofilm samples from one part of the Parisian drinking water distribution system. A dramatic change in bacterial population in the water during flow through the distribution system from the water treatment plant to the exit from the reservoir was found. The richness of the bacterial population was reduced from the water treatment plant to the reservoir (from 336 to 165 OTUs for water samples leaving the reservoir and from 947 to 275 for biofilm samples in the network). Several OTUs belonging to pathogenic genera were detected in our samples, mostly in the biofilm samples, thus suggesting that the biofilms may be an important source of bacteria during water distribution to the consumers.

Oligotrophic ecosystems can be loosely defined as environments that exhibit low ambient nutrient levels. During my thesis, I used 454 DNA pyrosequencing of partial 16S rDNA to explore the bacterial diversity in three different oligotrophic environments, including A. surface desert soil, B. Asian sandstorm dust and C. a section of the city of Paris's drinking water distribution system.A. Arid regions represent nearly 30% of the Earth's terrestrial surface. The living conditions at the surface of deserts are a challenge for microorganisms, as there is little available water and/or carbon, a very large range of temperatures and high exposure to UV irradiation from the Sun. In surface sand samples from two large Asian deserts, unexpectedly large bacterial diversity residing was revealed. Sequences belonging to the Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria phyla were the most abundant. An increase in phylotype numbers with increasing C/N ratio was noted, suggesting a possible role in the bacterial richness of these desert sand environments.B. Desert sandstorms are a meteorological phenomenon which have been postulated affect the Earth's climate and public health. We examined the particle-associated (dust and sand-associated) bacterial populations of atmospheric sand in the absence (as control) and presence of sandstorms in five Asian cities. Greater than 90% of the sequences can be classified as representing bacteria belonging to four phyla: Proteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. Principal component analyses showed that the sandstorm-associated bacterial populations were clustered by sampling year, rather than location. Members belonging to nine bacterial genera (Massilia, Planococcus, Carnobacterium, Planomicrobium, Pontibacter, Pedobacter, Lysobacter, Sanguibacter, Ohtaekwangia) were observed to increase in sand-associated samples from sandstorms, versus the controls. C. We characterized the bacterial communities in three water and three biofilm samples from one part of the Parisian drinking water distribution system. A dramatic change in bacterial population in the water during flow through the distribution system from the water treatment plant to the exit from the reservoir was found. The richness of the bacterial population was reduced from the water treatment plant to the reservoir (from 336 to 165 OTUs for water samples leaving the reservoir and from 947 to 275 for biofilm samples in the network). Several OTUs belonging to pathogenic genera were detected in our samples, mostly in the biofilm samples, thus suggesting that the biofilms may be an important source of bacteria during water distribution to the consumers.