http://hdl.handle.net/10027/7551 Tue, 21 May 2013 17:11:57 GMT 2013-05-21T17:11:57Z http://hdl.handle.net/10027/8730 Interaction of Carbon Dioxide with Na-exchanged Montmorillonite at Pressures to 640 Bars: Implications for CO2 Sequestration Giesting, Paul; Guggenheim, Stephen; Koster van Groos, August F.; Busch, Andreas Na-exchanged montmorillonite swells upon interacting with CO2 under the conditions P(CO2) ≤ 50 bars, T = 22-47°C, as shown by experiments in high-pressure environmental chambers using powder X-ray diffraction techniques. The amount of swelling depends on the initial H2O content of the montmorillonite. Maximum expansion, to 12.3 Å, occurred in a sample with an initial d(001) of 11.3 Å at P(CO2) = 57 bars. Thus, montmorillonite can expand by 9% in contact with CO2 where small amounts of H2O are present in the interlayer. Little to no expansion occurs for samples with an initial d(001) ≤ 10.0 Å or d(001) = 12.3 to 12.5 Å. The reaction with CO2 is complete by ~50 bars; increasing P(CO2) from 50 to 640 bars did not result in any significant further increase of d(001). This work shows that a smectite-rich cap rock above a carbon sequestration reservoir may be significantly altered by reacting with CO2. NOTICE: this is the author’s version of a work that was accepted for publication in International Journal of Greenhouse Gas Control. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in International Journal of Greenhouse Gas Control, [Vol 8, 2012 May] DOI:10.1016/j.ijggc.2012.01.011 Tue, 01 May 2012 05:00:00 GMT http://hdl.handle.net/10027/8730 2012-05-01T05:00:00Z http://hdl.handle.net/10027/8511 A dynamic physical model for soil temperature and water in Taylor Valley, Antarctica Hunt, H.W.; Fountain, A.G.; Doran, P.T.; Basagic, H. We developed a simulation model for terrestrial sites including sensible heat exchange between the atmosphere and ground surface, inter- and intra-layer heat conduction by rock and soil, and shortwave and longwave radiation. Water fluxes included snowmelt, freezing/thawing of soil water, soil capillary flow, and vapour flows among atmosphere, soil, and snow. The model accounted for 96–99% of variation in soil temperature data. No long-term temporal trends in soil temperature were apparent. Soil water vapour concentration in thawed surface soil in summer often was higher than in frozen deeper soils, leading to downward vapour fluxes. Katabatic winds caused a reversal of the usual winter pattern of upward vapour fluxes. The model exhibited a steady state depth distribution of soil water due to vapour flows and in the absence of capillary flows below the top 0.5 cm soil layer. Beginning with a completely saturated soil profile, soil water was lost rapidly, and within a few hundred years approached a steady state characterized by dry soil (,0.5% gravimetric) down to one metre depth and saturated soil below that. In contrast, it took 42 000 years to approach steady state beginning from a completely dry initial condition. © 2010 by Cambridge University Press, Antarctic Science DOI:10.1017/S0954102010000234 Sun, 01 Aug 2010 05:00:00 GMT http://hdl.handle.net/10027/8511 2010-08-01T05:00:00Z http://hdl.handle.net/10027/8448 Satellite ocean color algorithms: a review of applications to the Great Lakes Lesht, Barry; Barbiero, Richard; Warren, Glenn We review the literature relating to the retrieval of chlorophyll concentrations in the Great Lakes from satellite observations. Most studies show that the satellite estimates of lake chlorophyll concentration are linearly related to the observed concentrations, though they tend to overestimate concentrations at lower values and underestimate them at higher values. Deviations from a consistent, accurate, linear relationship can be attributed to temporal and spatial variations in the inherent optical properties of the color producing agents in the water as well as to varying concentrations of interfering substances such as suspended non-algal particles and colored dissolved organic matter. We confirmed these results by using a simple optical model to examine the sensitivity of the retrieved chlorophyll values to the concentrations of interfering substances and to differences in model parameters. Because the spatial and temporal optical properties of the Great Lakes are unpredictable, no retrieval method is likely to produce accurate results all the time. The papers we reviewed show that simple band ratio algorithms can provide chlorophyll estimates that are proportional to in situ concentrations. The bulk of the literature suggests that the band ratio methods will be of most value in regions where the concentrations of interfering substances such as dissolved organic material or suspended sediments are minimal. Because of these limitations we recommend that future papers presenting chlorophyll analysis based on satellite data provide confirming field observations that include measurements of suspended particles and dissolved organic carbon. We also recommend that Great Lakes scientists explore novel methods for retrieving chlorophyll concentrations from satellite observations that have proven useful in other optically complex waters. NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Great Lakes Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Great Lakes Research, Vol 38, Issue 1, (MAR 2012). DOI: 10.1016/j.jglr.2011.10.005 Thu, 01 Mar 2012 06:00:00 GMT http://hdl.handle.net/10027/8448 2012-03-01T06:00:00Z http://hdl.handle.net/10027/8390 Mantle Flow Beneath Arabia Offset from the Opening Red Sea Chang, Sung‐Joon; Merino, Miguel; Van der Lee, Suzan; Stein, Seth; Stein, Carol A. Continental rifting involves a poorly understood sequence of lithospheric stretching, volcanism, and mantle flow that evolves to seafloor spreading. We present new insight from inversion of seismic traveltimes and waveforms beneath Arabia and surroundings. Low velocities occur beneath the southern Red Sea and Gulf of Aden, consistent with active spreading. However, hot material extends not below the northern Red Sea, but is offset eastward beneath Arabia, showing mantle flow from the Afar hotspot. The location of this channel beneath volcanic rocks erupted since rifting began 30 million years ago indicates that flow moves with Arabia. We propose that the absence of seafloor spreading in the northern Red Sea reflects the offset flow. This geometry may evolve to spreading in the Northern Red Sea, rifting of Arabia, or both. This situation has aspects of both active and passive rifting, showing that both can occur before coalescing to seafloor spreading. Copyright 2011 American Geophysical Union. The original version is available through AGU at DOI: 10.1029/2010GL045852. Wed, 16 Feb 2011 06:00:00 GMT http://hdl.handle.net/10027/8390 2011-02-16T06:00:00Z