Soft X-ray spectromicroscopy studies of environmental interfaces

COLL 418

Gordon E. Brown Jr.1, Karim Benzerara2, Tae Hyun Yoon3, Juyoung Ha, jyha@stanford.edu1, Carmen D. Cordova4, Alfred M. Spormann4, Guillaume Morin5, Georges Calas5, and Tolek Tyliszczak6. (1) Department of Geological & Environmental Sciences and Stanford Synchrotron Radiation Laboratory, Stanford University, 450 Serra Mall, Braun Hall, Bldg. 320, Stanford, CA 94305-2115, (2) Institut de Minéralogie et Physique des Milieux Condensés, University of Paris 6 -7, 140 rue de Lourmel, 75015 Paris, France, (3) Department of Chemistry, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, South Korea, (4) Department of Civil and Environmental Engineering, Stanford University, Clark Center for Bio-X, Room E250, 318 Campus Drive, Stanford, CA 94305-5429, (5) Institut de Minéralogie et Physique des Milieux Condensés, Universiy of Paris 6 -7, 140 rue de Lourmel, 75015 Paris, France, (6) Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720
Environmental interfaces are the locations of most chemical reactions occurring in the environment and commonly juxtapose minerals, aqueous solutions, microbial organisms, and/or organic matter (including black carbon and xenobiotic organics). Fundamental understanding of the chemical and biological processes occurring at such interfaces is limited because of their complexity and the need to study them at appropriate spatial scales under realistic environmental conditions. We have conducted a series of studies of various environmental interfaces using scanning transmission x-ray microscopy (STXM) aimed at defining reaction products and conditions in several natural and model systems. MES STXM beam station 11.0.2.2 at the Advanced Light Source, which is capable of 25-30 nm spatial resolution over the energy range 75-2150 eV, was used for imaging and NEXAFS spectroscopy in the following interfacial systems: (1) aragonite-bacteria-EPS interfaces in a modern microbialite from Lake Van, Turkey, (2) Shewanella oneidensis MR-1-hematite interfaces in pH 7.4 solutions; (3) Gallionella-Fe(II) solution interfaces in an acid mine drainage (AMD) containing 350 mg/l of As(III) in Gard (Carnoulès), France, and (4) black carbon surfaces before and after interaction with polychlorinated biphenyls (PCBs). These studies have shown, respectively, that (1) the unusual morphology of microbialite aragonite crystals are due to crystal growth in a polysaccharide matrix; (2) differences in hematite particle size influence S. oneidensis cell activity and iron reduction rates; (3) Gallionella are capable of Fe(II) oxidation but not As(III) oxidation, resulting in the precipitation of tooeleite [Fe(III)6(AsO3)4(SO4)(OH)4•4H2O] in the Carnoulès AMD system; and (4) chemical heterogeneities in black carbon materials influence the sorption of hydrophobic organics like PCBs, which are found to adsorb preferentially to surface regions of black carbon with the highest content of aromatic functionalities.
 

Environmental Interfaces
2:00 PM-6:10 PM, Tuesday, 12 September 2006 Sir Francis Drake -- Empire Room, Oral

Division of Colloid & Surface Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006