CHEM 1223A

eldridge [at] umd [dot] edu

James Farquhar

Stable isotope geochemistry, isotope effects, ab initio molecular modeling, chemical kinetics, sulfur cycle, biosignatures.

My research focuses on stable isotope partitioning in the sulfur cycle using the multiple sulfur isotope approach. I use both experimental and theoretical modeling-based approaches (Gaussian quantum mechanical software) to determine isotope effects associated with chemical reactions and equilibria involving sulfur compounds. My current focus is on the kinetics and isotope effects associated with the oxidation of aqueous sulfur compounds (particularly sulfide and sulfite species), as well as equilibrium sulfur and oxygen isotope partitioning among a wide variety of aqueous and gaseous sulfur compounds. Although the majority of my research focuses on inorganic sulfur chemistry, I am also involved in applying these constraints to models of microbial sulfur metabolisms and determining the possibility of biosignatures for oxidative sulfur cycling processes. The overall goal of my research is to provide the necessary constraints to inform models that describe the complex abiological and biological sulfur cycling in surface environments.

Templeton, A.S., Knowles, E.J., Eldridge, D.L., Arey, B.W., Dohnalkova, A.C., Webb, S.M., Bailey, B.E., Tebo, B.M., & H. Staudigel. (2009) A Seafloor Microbial Biome Hosted Within Incipient Ferromanganese Crusts. Nature Geoscience. 2 872-876. DOI: 10.1038/ngeo696

Tostevin, R., Turchyn, A.V., Farquhar, J., Johnston, D.T., Eldridge, D.L., Bishop, J.K.B., McIlvin, M. (2014) Multiple sulfur isotope constraints on the modern sulfur cycle. Earth and Planetary Science Letters. 396 14-21. DOI: 10.1016/j.epsl.2014.03.057

Wankel, S.D., Bradley, A.S., Eldridge, D.L., Johnston, D.T. (2014) Determination and application of the equilibrium oxygen isotope effect between water and sulfite. Geochimica Cosmochimica Acta. 125 694-711. DOI: 10.1016/j.gca.2013.08.039

Eldridge, D. L., Farquhar, J. (2018) Rates and multiple sulfur isotope fractionations associated with the oxidation of sulfide by oxygen in aqueous solution. Geochimica et Cosmochimica Acta. 237 240-260. DOI: 10.1016/j.gca.2018.06.030