Experimental and theoretical investigation of the mobilization, immobilization and sequestration of subsurface metals through manipulation of carbonate equilibria

This dissertation investigates the forced mobilization, immobilization and sequestration of heavy metals and radionuclides in the ground water environment. Metal mobility/immobility can be effectively controlled by the manipulation of carbonate equilibria. Three different aspects of its potential application as an in situ remediation technology to clean up contaminated aquifers are investigated. A laboratory experiment was conducted to determine the effectiveness of CO2 partial pressure manipulation, acting as the driver of the carbonate equilibria system, to modify metal mobility in calcite-bearing soils. In a first step, mobilization occurs when CO2 is injected into the ground water lowering its pH; this forces the release of the metals bound to the solid phase. Down gradient, immobilization occurs when the excess CO 2 is removed from the ground water during air sparging, reversing the previous process by increasing the pH of the ground water and causing the metals to partition onto the solid phase. The results show that CO2 charging/air sparging effectively mobilized/immobilized Mn2+, Zn2+, Sr2+ and Ba2+. Predictions of mobilized and immobilized concentrations were made. These were based on the equilibrium exchange reaction of cations between the solid solution and the aqueous phase. The predicted results were in close agreement with the observed data. A second laboratory experiment was conducted to assess the effectiveness of solid solution formation through carbonate precipitation for the in situ remediation of ground water contaminated with heavy metals and radionuclides. The experiment simulated the flow of ground water through an inert isotropic porous medium. Three different treatments (calcium carbonate, metal carbonate, and pH) were compared to a control baseline run. Plumes of contamination containing Pb2+, Cd2+, Cu 2+, Mn2+, Zn2+, Co2+, Sr2+, and Ba2+ were intercepted by remediation zones generated by the injection of different treatment solutions. Metal carbonate precipitation was the most effective treatment in terms of aqueous metal removal, whereas calcium carbonate (calcite) treatment was the most effective in terms of pH stability. Based on these results a sequence of treatments is proposed where a major portion of contamination is precipitated as carbonates, followed by a calcite treatment to coat the other precipitates, to keep the system carbonate saturated and to further decrease the aqueous metals concentrations by coprecipitation. In addition to the two laboratory experiments, a computer model was developed to obtain information about both the substituting and non-substituting ions during solid solution formation and how their proportions affect the coprecipitation of the foreign ion. The governing equations of this model are based on a mass balance done in differential form of the main species present in the system, which is conceptually represented by a mixed flow reactor. An experimental reaction rate equation from the literature is used to approximate the reaction kinetics existent during the precipitation of calcite. Results indicate that coprecipitation increases when CO3 \u3e Ca. This occurs even for trace elements that preferentially partition into the aqueous phase

The simulated effects of dynamic stall on teeter response for wind turbines

Abstract not availabl

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

non present

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field