Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references (leaves 27-28). / Diapycnal mixing of ocean waters is crucial to the dynamics and associated heat transport of the meridional overturning circulation, yet uncertainty exists regarding the distribution and physical mechanisms of this mixing. This study uses a highly-idealized, single-hemisphere model of buoyancy-forced flow to examine the examine the effects of the transience of diapycnal mixing on the MOC. The strength of the MOC was found to be insensitive to mixing transience when mixing occurred uniformly on basin boundaries. For mixing that was highly localized in space, a ten-fold increase in transience, as compared with the time-invariant control, resulted in a decrease by about 20% of MOC mass and heat transport. The degree of sensitivity in the highly localized case is likely to be a strong function of the surface restoring timescale for temperature. The circulation dynamics associated with transient mixing displayed large-scale, complex oscillations that increased in amplitude with the transience of mixing. Attempts to quantify the relationship between mixing transience, MOC strength, and the power expended in mixing were inconclusive and merit further investigation. / by William R. Boos. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (leaves 115-118). / by Antonio De Lilla. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 103-109). / In this thesis, I study polycyclic aromatic hydrocarbons (PAHs) and perfluorocarboxylic acids (PFCAs). PAHs are by-products of burning and therefore have important anthropogenic sources in the combustion of fuels, biomass, etc. PFCAs and their atmospheric precursors are used in making firefighting foams, non-stick coatings, and other surfactant applications. I quantitatively examine the relative importance of uncertainty in emissions and physicochemical properties (including reaction rate constants) to Northern Hemisphere (NH) and Arctic PAH concentrations. NH average concentrations are more sensitive to uncertainty in the atmospheric lifetime than to emissions rate. The largest uncertainty reductions would come from precise experimental determination of PHE, PYR and BaP rate constants for the reaction with OH. I calculate long-chain PFCA formation theoretical maximum yields for the degradation of precursor species at a representative sample of atmospheric conditions from a three dimensional chemical transport model, finding that atmospheric conditions farther from pollution sources have both higher capacities to form long chain PFCAs and higher uncertainties in those capacities. I present results from newly developed simulations of atmospheric PFCA formation and fate using the chemical transport model GEOS-Chem, simulating the degradation of fluorotelomer precursors, as well as deposition and transport of the precursors, intermediates and end-products of the PFCA formation chemistry. I compare the model results to remote deposition measurements and find that it reproduces Arctic deposition of PFOA effectively. Given the most recent precursor emission inventory, the atmospheric indirect source of PFOA and PFNA is 10-45 t/yr globally and 0.2-0.7 t/yr to the Arctic. / by Colin Michael Pike-Thackray. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2006. / Cataloged from PDF version of thesis. Some pages in the original thesis contain text that is illegible. / Includes bibliographical references (pages 91-93). / As of 2002, 1.1 billion people lacked access to clean water, causing several million deahts each year from highly-infectious enteric diseases. It has been recognized that an appropriate way of addressing this problem may be to enhance the effectiveness and the usage of house-hold water treatment and storage (HWTS) systems. Ceramic filters are examples of HWTS systems. Ceramic filters decrease the concentration of bacteria by pore size filtration but are not able to filter the nanometer-size viruses. It is proposed that adding an adequate amount of metal oxides to the clay before firing the filters would allow the ceramic to adsorb the viruses present in the water. This thesis takes two steps towards evaluating this proposition. It demonstrates the microbiological methods needed to assess the presence of viruses in water and to carry out experiments with bacteriophages, used as model viruses. It also presents the theory necessary to understand, measure and model virus adsorption to surfaces. / by Marion Dumas. / S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998. / Includes bibliographical references. / The Cenozoic Baikal Rift Zone, one of the world's major continental rifts, is expressed as an approximately 1800 km-long southwest-northeast oriented system situated along a suture between the Archean Siberian craton and younger Paleozoic fold belts. Oligocene to Recent age volcanic rocks and associated mantle xenoliths are distributed in three major regions of the rift zone: the Udokan volcanic field in the northeast, the Vitim volcanic field -200 km southeast of Lake Baikal, and a broad zone of volcanism to the southwest of Lake Baikal. This large-scale study investigates the geochemical evolution of the Baikal Rift Zone volcanism using major element, trace element, and isotopic (Sr, Nd, and Pb) geochemistry, as well as 40Ar/39Ar geochronology. In addition, a detailed isotopic study of megacrysts provides insight into the relationship between megacrysts and host lavas and the nature of the lithospheric mantle. Results of this study suggest that the source region for Baikal Rift Zone volcanic rocks is remarkably homogeneous considering the large region and time span over which these rocks erupted, and that crustal contamination has not been a significant controlling factor. The Tunka Basin, Oka Plateau, and Tuva volcanic fields in the western Baikal Rift Zone, and the Vitim volcanic field southeast of Lake Baikal, have a fairly restricted compositional range from basaltic andesite, alkaline basalt and hawaiite, to basanite and mugearite. In the Udokan volcanic field in the northeast, a more evolved series of rocks ranging to trachytic compositions erupted across the suture between the Archean craton and Paleozoic fold belts. Major and trace elements indicate that fractional crystallization of pyroxene, olivine, and plagioclase produced the observed range in compositions. The trace element and isotopic compositions of Baikal Rift Zone volcanic rocks are comparable to those observed in ocean island basalts. The Sr, Nd, and Pb isotope systematics can best be explained by mixing between the end-member mantle components DMM ( typical of the depleted source of MORB mantle) and EMI (enriched mantle type 1). Megacrysts of clinopyroxene, amphibole, garnet, biotite, and anorthoclase mirror the isotope systematics of the host volcanic rocks, and suggest that the megacrysts were derived from a melt closely related to their host rocks. Furthermore, megacrysts of clinopyroxene, as well as Cr-diopside from spinel lherzolites, have an unradiogenic Pb isotopic composition that may be representative of the EMI-like composition of the subcontinental lithospheric mantle. / by Nancy Ruth Harris. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (leaves 171-182). / by Shui Xu. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Since their discovery in ancient sediments, hopanes and their biological precursors, bacteriohopanepolyols (BHPs), have been of great interest for their potential to serve as proxies for bacteria in the geological record. The validation of these and other biomarkers have implications for understanding the coevolution of organisms and the environment throughout Earth's history. 2-Methylhopanoids are of particular interest because their occurrence may be confined to cyanobacteria and alphaproteobacteria. Similarly, a stereoisomer of bacteriohopanetetrol (BHT), BHT II, has been identified exclusively in anaerobic ammonium oxidation (anammox) bacteria. However, the interpretation of sedimentary hopanoids is presently limited by an incomplete understanding of their phylogenetic associations, biological functions, and spatial and temporal disposition throughout diverse environments. I address some of these shortcomings through lipid biomarker characterization of water column and benthic microbial mat samples collected across geochemical and physiochemical gradients in the Eastern Tropical South Pacific oxygen minimum zone off the coast of northern Chile and in two ice-covered lakes of the McMurdo Dry Valleys, Antarctica. The results will enhance our ability to interpret the molecular fossil record, particularly those biomarkers that might preserve evidence of ancient marine and glacial environments. I will provide evidence that supports the use of BHT II as a biomarker for suboxia/anoxia, confirm the biosynthesis of 2- MeBHT in cyanobacteria as a response to photosynthetic stress, and describe improved methods that allow us to better detect, quantify, and interpret these markers in modern environments. / by Emily D. Matys. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Bibliography: p. 98-102. / by Tamara M. Wood. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (p. 212-220). / by Joseph H. LaCasce, Jr. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmosphere and Planetary Sciences, 1988. / Includes bibliographical references. / by Lorenzo M. Polvani. / Ph.D.