Statistical Emulation for Environmental Sustainability Analysis

The potential effects of climate change on the environment and society are many. In order to effectively quantify the uncertainty associated with these effects, highly complex simulation models are run with detailed representations of ecosystem processes. These models are computationally expensive and can involve computer runs of several days for their outputs. Computationally cheaper models can be obtained from large ensembles of simulations using a statistical emulation. The purpose of this thesis is to construct cheaper computational models (emulators) from simulation outputs of Lund-Potsdam-Jena-managed Land (LPJmL) which is a dynamic global vegetation and crop model. This research work is part of a project called ERMITAGE. The project links together several key component models into a common framework to better understand how the management and interaction of land, water and the earth’s climate system could be improved. The thesis focuses specifically on emulation of major outputs from the LPJmL model; carbon fluxes (NPP, carbon loss due to heterotrophic respiration and fire carbon) and potential crop yields (cereal, rice, maize and oil crops). Future decadal changes in carbon fluxes and crop yields are modelled as linear functions of climate change and other relevant variables. The emulators are constructed using a combination of statistical techniques of stepwise least squares regression, principal component analysis, weighted least squares regression, censored regression and Gaussian process regression. Further modelling involves sensitivity analyses to identify the relative contribution of each input variable to the total output variance. This used the Sobol global sensitivity method. The data cover the period 2001-2100 and comprise climate scenarios of several GCMs and RCPs. Under cross validation the percentage of variance explained ranges from 52-96% for carbon fluxes, 60-88% for the rainfed crops and 62-93% for the irrigated crops, averaged over climate scenarios

Coupled modelling of naturally occurring radionuclides in a cementitious engineered barrier

Constructing a robust numerical model that captures multi-mineral transformations, multiple chemical reactions, and secondary phase pathways in geological repositories is challenging due to uncertainties in parameters and a limited available database describing the kinetics of dissolution/precipitation reactions. In this work, combined with experiments, a comprehensive reactive transport model is used to study the chemical and physical interactions among radionuclides, cement leachate and the host rock in a nuclear waste repository. Hence, the modelling efforts will enhance the understanding of the transport of radionuclides in complex soil/rock systems and highlight the critical factors driving their migration in soils/rocks. To achieve these aims, the modelling of the radionuclide migration process was first investigated, considering all possible reactions that could take place. Then, the PHREEQC software was used for the numerical simulation, and experimental data were used to validate the model. The experiment studied a system for 15 months and 15 years with young cement leachate (pH=13) and intermediate cement leachate (pH = 10.8), respectively. Then, with the dissolution/precipitation kinetics implemented and verified, the transport process was incorporated with the aim of building a geochemical model that will describe the multimineral mass transfer under different conditions. Furthermore, the geochemical model was constructed to ensure the porosity evolution of the porous medium. Finally, radionuclide migration was incorporated into the model to characterise the effect of the sorption process. These studies showed that fluid chemistry controls the dissolution/precipitation of the primary minerals, which will control the long-term chemical equilibria and mineralogical composition of the host rock impacted by the alkaline leachate. Meanwhile, the chemical interaction between hyper-alkaline leachate and the host rock results in a series of mineralogical reactions, including cycles of minerals dissolution and precipitation (calcium silicate hydrate gel, C-S-H phases, C-A-S-H phases, hydrated silicate, and Na-Ca zeolites). Furthermore, by coupling the mineral volume changes and porosity evolution to the dissolution/precipitation reaction model, the results showed a better fit in ion concentration compared to the fixed porosity model, as it led to a more reactive surface area with the cement leachate. Moreover, the model shows that the dissolution of primary minerals in the host rock is the initial driving mechanism for the chemical evolution of the system. At the same time, the subsequent precipitation of several secondary phases controls the host rock's long-term chemical equilibria and mineralogical composition. Lastly, the sorption of uranyl (UO2_2+ (U_VI)) was found to strongly depend on the surface complexation model assumed, with no significant removal of U_VI by precipitation or ion exchange process. Furthermore, uranyl adsorption by the C-S-H phase was found to be minimum, which could be related to the lack of surface complexation parameters for C-S-H minerals

Annual Report of the University, 2001-2002, Volumes 1-4

VITAL ACADEMIC CLIMATE* by Brian Foster, Provost/Vice President of Academic Affairs A great university engages students and faculty fully in important ideas and issues ... not just to learn about them, but to take them apart and put them back together, to debate, deconstruct, resist, reconstruct and build upon them. Engagement of this sort takes concentration and commitment, and it produces the kind of discipline and passion that leads to student and faculty success and satisfaction in their studies, research, performance, artistic activity and service. It is also the kind of activity that creates a solid, nurturing spirit of community. This is what we mean when we talk about a vital academic climate. We are striving for an environment that will enrich the social, cultural and intellectual lives of all who come in contact with the University. Many things interconnect to make this happen: curriculum, co-curricular activities, conferences, symposia, cultural events, community service, research and social activity. Our goal is to create the highest possible level of academic commitment and excitement at UNM. This is what characterizes a truly great university. *Strategic Direction 2 New Mexico native Andres C. Salazar, a Ph.D. in electrical engineering from Michigan State University, has been named the PNM Chair in Microsystems, Commercialization and Technology. Carrying the title of professor, the PNM Chair is a joint appointment between the School of Engineering and the Anderson Schools of Management. Spring 2002 graduate John Probasco was selected a 2002 Rhodes Scholar, the second UNM student to be so honored in the past four years. The biochemistry major from Alamogordo previously had been awarded the Goldwater Scholarship and the Truman Scholarship. Andres c. Salazar Biology student Sophie Peterson of Albuquerque was one of 30 students nationwide to receive a 2002-2003 Award of Excellence from Phi Kappa Phi, the oldest and largest national honor society. Regents\\u27 Professor of Communication and Journalism Everett M. Rogers was selected the University\\u27s 4 71h Annual Research Lecturer, the highest honor UNM bestows upon members of its faculty. John Probasco honored by Student Activities Director Debbie Morris. New Mexico resident, author and poet Simon}. Ortiz received an Honorary Doctorate of Letters at Spring Commencement ceremonies. Child advocate Angela Angie Vachio, founder and executive director of Peanut Butter and Jelly Family Services, Inc., was awarded an Honorary Doctorate of Humane Letters. American Studies Assistant Professor Amanda}. Cobb won the 22 d annual American Book Award for listening to Our Grandmothers\\u27 Stories: The Bloomfield Academy for Chickasaw Females, 1852-1949