Erosion corrosion of plumbing materials in domestic water systems is a complex phenomenon driven by water quality, hydrodynamic and electrochemical factors. Erosion corrosion accounts for over a third of copper hot water system failures in the U.S., hundreds of millions in damage, and may be expected to increase with newer Legionella control strategies including increased use of water recirculation and high temperatures. Additionally, some nonleaded alloys introduced after the passage of a new federal law restricting lead content in plumbing, have been anecdotally implicated as failing prematurely from erosion corrosion compared to traditional alloys. This dissertation includes 1) a critical review of the literature, 2) investigation of a recent rapid erosion corrosion failure in a large building plumbing system, 3) replication of this phenomena in copper and nonleaded brass in laboratory studies, and 4) evaluation of 12 nonleaded alloys against conventional leaded brass. Current plumbing codes and guidelines to prevent erosion corrosion were found to be widely inconsistent and lacking scientific evidence. Large-scale recirculating hot water pipe-loop experiments demonstrated that an aggressive hard water with entrained aragonite (CaCO3) particles could cause fully penetrative failures (i.e., leaks) in brand new copper pipe and nonleaded brass fittings in just 3-49 days. This represents the first time rapid erosion corrosion failures have ever been replicated in the laboratory under conditions similar to those encountered in practice. The entrained particulates dramatically accelerated attack on metals, especially at pipe bends. In general, lowering pH, increasing flow velocity, increasing temperatures, entrainment of particles (of bigger sizes), and addition of chlorine disinfectant increased erosion corrosion rates. These results scientifically proved that hard waters are not inherently less aggressive than soft water, and in fact if CaCO3 solids form they can be much more aggressive. Finally, cavitation and erosion corrosion resistance of 12 nonleaded alloys was evaluated against leaded brass; stainless steels demonstrated superior performance, silicon brass had the greatest susceptibility and remaining alloys were in the middle. This performance data can aid decision making regarding choice of alloys for various water applications. Our work over the years, including involvement in the Flint Water Crisis, demonstrated that practicing trustworthy science as a public good requires commitment to scientific rigor, truth-seeking, managing conflicts of interest, and comprehensible evidence-based science communication. Critical problems in 21st century public science were highlighted including perverse incentives, misconduct, postmodernist "science anarchist" thought, and ineffectiveness of U.S. water utilities in communicating tap water safety to the American public. / Ph. D.

Un nouveau procédé, basé sur une adaptation innovante du principe de protection cathodique des ouvrages métalliques en milieu marin, consiste à favoriser la précipitation d’un agglomérat calcomagnésien sur plusieurs centimètres d’épaisseur. En présence de sable et de coquillages, cet agglomérat pourrait permettre de stabiliser des zones littorales en cours d’érosion ou d’améliorer l’ancrage d’enrochements brise-lames. L’objectif de ce travail est d’étudier et de comprendre les mécanismes réactionnels de formation de cet agglomérat permettant une précipitation en volume loin de la cathode afin d’en optimiser la vitesse de formation ainsi que ses propriétés mécaniques. Premièrement, il a été montré dans ces travaux que le milieu électrolytique pouvait influer sur la croissance du dépôt, avec une possible inhibition de formation de carbonate de calcium pour les faibles potentiels. L’influence des produits de corrosion dans le mécanisme de protection cathodique a également été mise en évidence grâce à des polarisations effectuées dans NaCl, eau de mer artificielle et naturelle. Deuxièmement, des essais d’un mois en courant imposé ont été menés du laboratoire jusqu’au site naturel, afin de se rapprocher des conditions réelles. La densité de courant appliquée ainsi que les conditions hydrodynamiques sont des facteurs clefs étroitement liés l’un à l’autre, influant sur la masse et le rapport Ca/Mg. Ces travaux ont aussi permis de mettre en avant l’influence du temps de polarisation sur la composition du dépôt calcomagnésien, présentant une cinétique de croissance stable mais une fluctuation de composition après 15, 30 et 60 jours. Cette variation interne du rapport Ca/Mg, attribuée à un processus de « dissolution/précipitation » dépendant du gradient de pH, ainsi que la répartition de ces éléments au sein du dépôt pourraient jouer un rôle majeur dans l’évolution de la tenue mécanique du dépôt au cours du temps. / A new method, based on an innovative adaptation of cathodic protection principle of metal structures in marine environment, is to promote the precipitation of a calcareous agglomerate several centimeters thick. In the presence of sand and shells, this cluster could stabilize coastal areas being eroded or improve anchorage of breakwater riprap. The objective of this work is to study and understand the reaction mechanisms allowing to create a voluminous calcareous deposit away from the cathode and to optimize deposition time as well as its mechanical properties. First, it was shown in this work that the electrolytic medium could affect the growth of the deposit, with a possible inhibition of formation of calcium carbonate fot the low potential. The influence of corrosion products in the cathodic protection mechanism was also highlighted through polarizations performed in NaCl, artificial and natural sea water. Second, one month test with impressed current were conducted from laboratory to natural site, in order to get closer of real conditions. Current density and hydrodynamic conditions are key factors closely bonded to each other, affecting the mass and composition of the Ca/Mg ratio. This work has also helped to highlight the influence of the polarization time on the composition, with stable growth kinetics but a composition’s evolution after 15, 30 and 60 days. This internal variation of the Ca/Mg ratio attributed to a process of « dissolution/precipitation » is pH dependent and the distribution of these elements within the deposit could play a major role in the evolution of the mechanical strength of deposit over time.

Phreatic overgrowths on speleothems (POS) are one of many sea-level proxies available to Quaternary geologists in Mallorca; these carbonate encrustations form at the air-water interface in cave passages flooded with brackish water. POS are ideal for reconstruction of western Mediterranean sea level because they are widespread in Mallorca's caves, can be precisely dated by U-series methods, constrain sea-level stands to sub-meter elevation, and are well preserved and accessible in the subterranean environment. This research investigates the POS depositional environment, which is relatively understudied compared to the other proxies used for sea-level reconstructions. This disparity has led to assumptions on many aspects of the POS precipitation. Further, POS are typically composed of calcite, but sometimes the metastable polymorph aragonite is present instead. Two caves were studied because of the presence of a modern POS horizon of aragonite and calcite: Cova des Pas de Vallgornera (Vallgornera) and Coves del Drac (Drac), respectively. High-resolution air and water physical parameters were collected for the first time, along with monthly water samples for stable isotope and elemental analysis. This 16-month record was supplemented with detailed geochemical studies throughout the project, including water-column profiles and CO2 sampling campaigns. The water level in both caves preserves the semi-diurnal Mediterranean Sea tide signal, with a lag of approximately four hours. The fluctuation in both caves is slightly attenuated, and the direct effects of barometric pressure and precipitation could not be discerned from the primary control of tidal pumping. Calculations based on salinity and isotope analysis show that less than 20% of the solution in each cave is seawater. Degassing of CO2 from the cave water to air was documented at both locations, with sporadic calcium carbonate supersaturation. These conditions are strongly dependent on annual cave ventilation, which becomes active during winter when cold, dense tropospheric air sinks into the subsurface. In addition to seasonal thermo-circulation, fluctuating water level displaces cave air and likely initiates tropospheric exchange throughout the year. This process primarily occurs through fissures in thin overlying bedrock at Vallgornera and through the large entrance in Drac. Higher elemental ratios (Mg:Ca, Sr:Ca, Mg:Sr) known to enhance aragonite precipitation or inhibit calcite precipitation were recorded in Vallgornera's water. A linear correlation with salinity was not observed, so higher ratios in Vallgornera must be contributed from differences in lithology, bedrock weathering intensity, or nearby rising thermal waters. In summary, this research confirms POS strengths as sea-level proxies from geochemical and hydrological perspectives. These carbonate encrustations are precipitated at the air-water interface, which fluctuates as an attenuated expression of Mediterranean Sea tide. Degassing of CO2 from the cave water to air, which promotes calcium carbonate supersaturation, is the major control on POS deposition, and is facilitated by winter ventilation and likely water-level fluctuations. CO2 degassing (and theoretically precipitation of POS) in isotopic equilibrium is possible in caves with restricted ventilation (small/sealed entrances, small passages). Aragonite may be precipitated instead of calcite because of local modifications to the geochemical system from bedrock weathering or contributions from deep groundwater.

On retrouve CaCO3 dans de nombreux matériaux du Vivant, comme par exemple le corail, les carapaces et les coquilles de différents crustacés et mollusques. La croissance des différentes formes allotropiques de CaCO3 , aragonite, calcite et vatérite, en présence de molécules biologiques, est influencée en terme d'organisation cristalline, de microstructure et d'ordre à grande échelle (texture et ultrastructure). La voie électrochimique a été choisie dans ce travail pour sa vitesse de formation de dépôt ainsi qu'un bon contrôle des paramètres instrumentaux. Nous avons sélectionné l'aragonite dans le dépôt ainsi que sa croissance texturée rappelant celle de la nacre de Haliotis tuberculata tuberculata avec toutefois une orientation cristalline moins prononcée. Une croissance en plaquettes pseudo-hexagonales orientées, présentant un double-maclage et une orientation d'environ 60° les unes par rapport aux autres, rappelle les observations faites sur les nacres de différents mollusques. Une étude par diffraction des rayons X sur des dépôts obtenus en présence de chitosan et de molécules organiques extraites de nacres naturelles montre leur influence sur la texture cristalline, les mailles de l'aragonite et les groupements carbonate. Le décalage de l'atome de carbone par rapport au plan des oxygènes de ce groupement révèle la déformation induite par les molécules durant la croissance cristalline. Cette étude montre que par une approche minérale-organique synthétique, on peut se rapprocher des processus conduisant à la croissance d'organo-cristaux naturels, pour la texture, la distortion de mailles, la structure et le faciès cristallin.

A monthly resolved coral δ18O record from Sabine Bank, Vanuatu (SBV; 166.04° E, 15.94°S), extending from 2006 to 1929 CE, is used to assess the influence of sea surface salinity (SSS) on the oxygen isotopic composition of coral aragonite at this location. Monthly SSS anomalies at SBV between 2006 and 1970 are strongly correlated with monthly anomalies in sea surface temperature (SST) variations in the central Pacific cold tongue, as recorded by SST anomalies in the Niño 3.4 grid box (i.e., canonical record of ENSO variability, r = 0.68, p < 0.01; lag of 6 months). This relationship demonstrates that SSS in the waters offshore of Vanuatu respond to ENSO-driven changes in the coupled ocean-atmosphere system in the tropical Pacific. SBV coral δ18O is also strongly correlated with monthly instrumental SSS anomalies at Vanuatu (r = 0.71, p < 0.01), therefore SBV coral δ18O variations are driven by the ENSO-related changes in surface ocean conditions. A calibration-verification exercise using SBV coral δ18O values and instrumental SSS was performed over the period 2006-1970 CE. A statistically robust transfer function was determined and used to predict SSS at SBV back to 1929 CE. The coral δ18O and SSS relationship at Vanuatu is further evaluated via comparison with a coral δ18O record from Malo Channel, Vanuatu, a site that is 130 km to the east of SBV. The strong correlation between the two coral δ18O records (r = 0.70; p < 0.01) suggests that ENSO drives regional changes in SSS in this region and that such changes can be reconstructed using variations in skeletal δ18O of corals. / text

Les microbialites sont des roches organo-sédimentaires dont les processus de formation restent mal compris. L'objectif central de cette thèse est de mieux comprendre les conditions environnementales permettant le développement de microbialites actuels provenant de 10 lacs volcaniques mexicains. Une grande diversité de compositions minéralogiques des microbialites a été observée, comprenant divers carbonates et la quasi omniprésence de silicates de magnésium authigènes. A partir de cette étude nous proposons une valeur minimale d'alcalinité permettant le développement des microbialites. De plus, une corrélation positive entre l'alcalinité et la teneur en sodium des lacs est apparue. Cette corrélation pourrait s'expliquer par des niveaux différents d'évaporation des lacs et/ou des degrés différents d'altération des silicates alentours. L'étude plus particulière des silicates de magnésium a révélé que ces phases sont faiblement cristallisées, semblables à la kérolite et ont un fort potentiel de fossilisation des microorganismes et de la matière organique. Ces silicates de magnésium sont parfois associés à du fer dont l'origine pose question dans ces environnements alcalins et oxygénés. Nous avons mis en évidence la présence de différents types de phases porteuses du fer : des hydroxydes doubles lamellaires (hydrotalcites), des oxy(hydroxy)des, des silicates de magnésium et des sulfures. Nous proposons plus spécifiquement que l'hydrotalcite pourrait être issue de l'altération des basaltes par la circulation de fluides souterrains et plus généralement que cette phase pourrait être un précurseur des silicates de magnésium abondamment observés dans les microbialites actuels. / The processes leading to the formation of microbialites, which are organo-sedimentary rocks, are not well understood. The main goal of this thesis is to better understand the environmental conditions allowing the development of modern microbialites. Here we performed geochemical analyses of water solutions and mineralogical analyses of microbialites in 10 Mexican volcanic lakes. We found a large diversity of microbialites in terms of mineralogical composition, with occurrence of diverse carbonate phases as well as the frequent presence of authigenic magnesium silicate phases. From this study, we infer a minimum alkalinity value for the formation of lacustrine microbialites. Moreover, we observe a positive correlation between the alkalinity and the sodium content of the lakes. This may relate to variations in evaporation intensity and/or various degrees of weathering of the surrounding silicates. The study of Mg-silicates revealed that this phase is similar to kerolite, a poorly crystalline hydrated talc phase, and has a strong potential for the fossilization of microorganisms and organic matter. These silicates are sometimes associated with iron, the origin of which remains uncertain in these alkaline and oxidized environments. By the mineralogical study of several microbialites, we found several phases bearing iron: layered double hydroxides (hydrotalcites), Mg-silicates, oxy(hydroxi)des and sulfides. We propose more specifically that hydrotalcite could be the by-product of basalts weathering by groundwater. We propose more generally that hydrotalcite could be a precursor phase of Mg-silicates abundantly observed in modern microbialites.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18088号 / 理博第3966号 / 新制||理||1572(附属図書館) / 30946 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 下林 典正, 教授 土`山 明, 准教授 三宅 亮 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Coral reefs are an important element of marine ecosystem that are critical to maintain a healthy environment. Unfortunately, in recent years coral reefs are doing poorly and many in parts of the ocean are simply dying. Therefore, study of coral’s structural response to external loads could answer what will happen with their structures, while they exhibit different types of loading. Therefore, the proposition of using in-situ micro-Raman spectroscopy to study skeletons of Acropora cervicornis was used. Coral skeleton samples I subjected to mechanical loading studied their vibrational properties by exciting the material with 532nm visible light. A uniaxial compressive load I applied using a MTS universal testing machine and then using the Raman Spectroscopy to study the vibrational response of coral skeletons. Indentations used Vickers Hardness tester and performed 2D mapping of the coral structure around the indentation. If it’s expected that as a result of the proposed research the better understanding of structural stability of the Acropora Cervicornis coral skeletons will be achieved.

Deep-water or cold-water corals are abundant and highly diverse, greatly increase habitat heterogeneity and species richness, thereby forming one of the most significant ecosystems in the deep sea. Despite this remote location, they are not removed from the different anthropogenic disturbances that commonly impact their shallow-water counterparts. The global decrease in seawater pH due to increases in atmospheric CO2 are changing the chemical properties of the seawater, decreasing the concentration of carbonate ions that are important elements for different physiological and ecological processes. Predictive models forecast a shoaling of the carbonate saturation in the water column due to OA, and suggest that cold-water corals are at high risk, since large areas of suitable habitat will experience suboptimal conditions by the end of the century. The main objective of this study was to explore the fate of the deep-water coral community in time of environmental change. To better understand the impact of climate change this study focused in two of the most important elements of deep-sea coral habitat, the reef forming coral Lophelia pertusa and the octocoral community, particularly the gorgonian Callogorgia delta. By means of controlled experiments, I examined the effects of long- and short-term exposures to seawater simulating future scenarios of ocean acidification on calcification and feeding efficiency. Finally In order to understand how the environment influences the community assembly, and ultimately how species cope with particular ecological filters, I integrated different aspects of biology such functional diversity and ecology into a more evolutionary context in the face of changing environment. My results suggest that I) deep-water corals responds negatively to future OA by lowering the calcification rates, II) not all individuals respond in the same way to OA with high intra-specific variability providing a potential for adaptation in the long-term III) there is a disruption in the balance between accretion and dissolution that in the long term can shift from net accretion to net dissolution, and IV) there is an evolutionary implication for certain morphological features in the coral community that can give an advantage under stresfull conditions. Nevertheless, the suboptimal conditions that deep-water corals will experience by the end of the century could potentially threaten their persistence, with potentially negative consequences for the future stability of this already fragile ecosystem. / Biology