Indiana University Bloomington

Fall 2011

August 29: On Monday, August 29th in lieu of colloquium, we invite all students, faculty, family, and friends of the Department of Geological Sciences to a welcome reception and dinner for Jackson and our new graduate students at the Stone Age Institute which is Co-Directed by Nick Toth and Kathy Schick.  If you have never seen the stone tower or the great hall then you are in for a visual treat.

September 5: Labor Day, no colloquium

September 12: Youxue Zhang, University of Michigan. Title: "Kinetics of Transport-Controlled Growth and Dissolution of Bubbles and Minerals In Melts and Water"

Abstract: Kinetics of transport-controlled growth and dissolution of a particle (either a crystal, or a droplet, or a bubble) in a liquid (a melt or water) is a class of problems often encountered in petrology, volcanology and geochemistry. For example, petrologists have investigated and developed models to predict the equilibrium or fractional crystallization sequence in a given magma, and partial melting in the mantle. However, it was not possible to estimate the rate of processes such as mineral growth and dissolution in a melt, especially due to the complicated role of convection. Recent advancement allows these kinetics to be quantified. In the presence of forced convection, the growth or dissolution rate is estimated using relations among dimensionless parameters. I will use the following examples to illustrate the principles: diffusive bubble growth in rhyolitic melt (volcanology), convective bubble growth in beer, CO2 droplet dissolution in water (carbon sequestration), and transport-controlled mineral dissolution and growth (petrology).

September 19: Chris Craft, SPEA Title: "Tidal Wetlands and Climate Change"

September 26: Darby Dyar, Mt. Holyoke College. Title: "Water on Mars: When, Where, Why?"

October 3: Arndt Schimmelmann, IU Geological Sciences Title: "Hydrogen fuel: technical opportunities and challenges."

Abstract: Hydrogen is the most abundant atom in the universe where elemental hydrogen H2 may represent more than 90% of all molecules. Earth is a cosmic oddball, because in our oxygenated atmosphere H2 accounts only for about 0.00005 volume%. In spite of the fact that the oxidation of H2 with O2 to form water releases much energy that can be used as heat or be converted to electricity, there have been numerous obstacles preventing the widespread use of hydrogen as fuel.

Hydrogen had been recognized in 1766 by Henry Cavendish as a substance distinct from other flammable gases, but its technical use as a fuel remained limited throughout the 19th and 20th centuries to that of a by–product generated from coal during pyrolysis. Hydrogen has been afflicted by the stigma of being a highly combustible and accident–prone gas. The inevitable approach of "Peak Oil" triggered interest in non–carbon-based fuel for transportation. In recent years, hydrogen has been touted as a clean energy source because its oxidation by combustion or catalytic conversion in fuel cells generates pure water and no carbon dioxide. Hydrogen technologies gained interest for short–term energy storage and buffering peak demand for electricity, for example by generating and storing hydrogen gas during periods of excess electricity from wind parks, and then catalytically generating electricity from stored hydrogen when wind power is insufficient.

Today hydrogen is mostly produced commercially by catalytic reactions of steam with natural gas or coal. Most of the produced hydrogen is subsequently used on site for chemical or energy use. The combustion of pure hydrogen in advanced gas turbines can reach relatively high electrical energy yields that can offset the parasitic expense of carbon sequestration and thus strengthen the economic basis for "clean coal" technologies. The future of hydrogen as a transportation fuel remains in doubt and depends on progress towards compact storage of hydrogen.

October 10: GSA Meeting in Minneapolis, no colloquium

October 17: David Princhu, University of Georgia. Title: "Impacts of Global Change on Freshwater Ecosystems: The View From the Intermountain West of the United States"

October 24: Laura Johnson, SPEA Title: "Carbon and nitrogen cycling in streams and watersheds influenced by agriculaural activities."

Abstract: Agricultural activities have increased nitrogen (N) availability in streams and watersheds throughout the Midwest. In streams, N is a critical nutrient and can become a pollutant under excess concentrations. My current research is focused on how this excess N interacts with carbon cycling in an agricultural watershed. In streams, dissolved organic carbon (DOC) is a resource for heterotrophic microbial communities; however, the composition of DOC has been altered in agricultural streams. Across aquatic ecosystems, C and N cycling are tightly linked through metabolic processes. However, the coupling of C and N cycling at an ecosystem scale is not well understood, particularly in streams influenced by agricultural activities, where the balance of these nutrients has been shifted. We have used two approaches to address this topic.

First, we conducted labile DOC additions in two streams in Indiana to test the strength of coupling between N cycling and water–column DOC. Then, we examined whether we could observe these linkages between N cycling and DOC availability throughout an agricultural watershed during 7 distinct hydrological and biological conditions. Our results so far suggest that DOC in the water column has little influence on denitrification, the permanent removal of N. This was surprising because DOC is the electron donor for denitrification and can be a limiting factor for this process. Instead, it appears that organic matter in the sediments may be the source of C for denitrifiers. Overall, these results indicate that coupling between water–column DOC and N cycling in streams may be spatially constrained, which has implications for our understanding of N retention in streams.

October 26: Special Colloquium, Nancy Rose Mineralogical Society of America Distinguished Lecturer. Lunchtime Seminar title: "Exploring Hydrogen Environments in Minerals" 12:00-1:00 S201. Colloquium title: "A New View of Bonding in Molecules, Minerals and Beyond" 4:00, GY143.

Abstract: Victor Goldschmidt and Linus Pauling laid the basis for the fields of geochemistry and crystal chemistry using the ionic model. Indeed, Goldschmidt's structural principles for ionic crystals were summarized by Pauling in a series of Rules to predict the structures and stabilities of ionic solids. Although the concepts of cations vs. anions, ionic radii, coordination number and polyhedral building blocks have greatly aided our understanding of oxides and silicates, such an approach has limitations when applied to complex minerals that display multiple types of bonding. One approach that shows great promise to unify our view of bonding in minerals is based on calculating the electron density distributions of minerals. Since G.V. Gibbs' pioneering work that showed that molecular orbital studies of molecules can be used as models for bonding in silicates, computational quantum chemistry has become a powerful tool in mineralogy. Electron density distributions of minerals can now be calculated which show excellent agreement with electron density distributions derived from X-ray diffraction experiments. Using the analysis developed by R. Bader for atoms in molecules, the bond paths and bond critical point properties of atoms in mineral structures can be evaluated from the topology of their electron density distributions. Such studies have been completed on a variety of compounds ranging from molecules, molecular crystals, oxides, silicates, sulfides, arsenides and even to large macromolecules such as proteins, providing new insight into the bonded interactions that are present across this diverse range of structures. These studies have elucidated systematic relationships between structural and physical properties of minerals as well as furnishing new insights into the many types of reactions involving minerals.

October 31: Michael Coats, University of Chicago. Title: "Walks on shale: the origin of tetrapods in the mid-Paleozoic."

November 7: Jeremy Dunning, Geological Sciences. Title: "Using Technology and Teaching"

November 14: Lynn Pace/Pat Carroll, IDEM. Title: "Careers in state agencies and water quality issues in Indiana"

November 21: Thanksgiving Break, no colloquium

November 28: John Steinmetz, Indiana Geological Survey. Title: "After 175 years, there's always something new at the Indiana Geological Survey."

December 5: AGU Meeting and Interview for Shrock hire(s), no colloquium