Argonne National Laboratory

Kenneth Kemner

Physicist & Group Leader

Major Accomplishments (K. Kemner)

 

Development of a synchrotron-based Biogeochemical Research Program and the Molecular Environmental Science Research Group

In 1996, when I began working in the Environmental Research Division at Argonne National Laboratory, the extent of the use of synchrotron radiation for Environmental research was confined primarily to Geochemical research with limited examples of extension of the technology to the study of heavy metal uptake in plants and animals.  Since then, we have worked to develop an integrated multi-disciplinary research group that is recognized around the world as having expertise in the application of synchrotron radiation provided by the Advanced Photon Source (APS) to the study of Biogeochemistry (with an emphasis on the microbial components of Biogeochemistry).  In addition, in collaboration with the MRCAT (I have been a member of the MRCAT Executive Committee since 1996) we have also worked to develop the EnviroCAT at the APS.  The EnviroCAT is a sector at the APS that is focused on developing x-ray absorption-based techniques to address environmental science questions.-  While research groups like ours have usually emphasized either expertise in Biogeochemistry or synchrotron radiation techniques, a unique attribute or our group is equal, highly qualified expertise in both Biogeochemistry and synchrotron radiation techniques.  Since 1996, the number of researchers who apply synchrotron radiation to biogeochemical research has grown to the hundreds.  In addition, many groups have emulated our approach and are now emphasizing expertise in both synchrotron radiation-based approaches and Biogeochemistry. 

 

High Energy X-ray Fluorescence Imaging of Bacterial Cells

In late 1997, no one had articulated the idea of using high-energy x-ray radiation for x-ray fluorescence imaging of bacterial cells.  Having already recognized the importance of biofilms and microorganisms in environmental and biogeochemical research, when the opportunity to produce submicron-scale x-ray beams with Fresnel zone plates at the APS became available, we recognized the unique opportunity of being located at Argonne near the APS to develop this capability.  During the next ~5 years, we worked with beam line scientists at sector 2 at the APS to develop the capability to image bacteria while also developing the Microbiology and Biogeochemistry capabilities within my research group.  In 2000 and 2004, via publications in Science (M. Labrenz, G. K. Druschel, T. Thomsen-Ebert, B. Gilbert, S. A. Welch, K. M. Kemner, G. A. Logan, R. E. Summons, G. De Stasio, P. L. Bond, B. Lai, S. D. Kelly, J. F. Banfield, “Sphalerite (ZnS) deposits forming in natural biofilms of sulfate reducing bacteria,” Science 290 1744-1747, 2000; K. M. Kemner, S. D. Kelly, B. Lai, J. Maser, E. J. O’Loughlin, D. Sholto-Douglas, Z. Cai, M. A. Schneegurt, C. F. Kulpa, Jr., K. H. Nealson, “Elemental and Redox Analysis of Single Bacterial Cells by X-ray Microbeam Analysis,” Science 306 686-687, 2004.) we successfully demonstrated that bacteria and their biomineralization products could be imaged via the spatial distribution of their elemental makeup.  Since that time, we have had numerous high profile publications that have made use of this technique to address key biogeochemistry questions for the US DOE.

 

An In-depth Understanding of Uranium Biogeochemistry; Identification of Nanoparticulate Uraninite and Monomeric Reduced Uranium

Beginning in 2000, my group began to investigate biogeochemical redox reactions related to uranium.  At that time most synchrotron-based research of uranium was limited to lab-based samples with concentrations that were artificially elevated by the researchers so as to enable x-ray measurements of the samples.  Around that time we recognized the unique capabilities that an undulator beam line at the APS could provide to investigate environmental samples contaminated with levels of uranium similar to the lower concentrations found in natural soils and sediments.  Over the next few years, we optimized the EnviroCAT/MRCAT undulator beam line for high throughput measurement of uranium in soils and sediments.  As a result of that, our Molecular Environmental Science Group (now referred to as the Microbial Ecology and Biogeochemistry Group) is world renowned for our ability to collect and analyze U XAFS data and to interpret the results in the context of biogeochemically-driven redox reactions.  Of particular note are our discoveries of the formation of chemically reduced uranium existing in the form of nanoparticulate uraninite and, more recently, monomeric reduced uranium (Y. Suzuki, S. D. Kelly, K. M. Kemner, J. F. Banfield, "Nanometer-size products of uranium bioreduction,” Nature 419 134, 2002; K. E. Fletcher, M. I. Boyanov, S. H. Thomas, Q. Wu, K. M. Kemner, F. E. Loeffler, “U(VI) Reduction to Mononuclear U(IV) by Desulfitobacterium Species,” Environ. Sci. Technol. 44 4705-4709, 2010; M. I. Boyanov, K. E. Fletcher, M. Kwon, E. O’Loughlin, T. Shibata, F. E. Loffler, K. M. Kemner, “Solution and Microbial Controls on the Formation of Reduced U(IV) Species,” Environ. Sci. Technol. 45 8336-8344, 2011).

 

Creation of the Synchrotron Environmental Science (SES) Conference Series and its elevation to the flagship Conference of EnviroSync

In the process of developing the EnviroCAT and the Molecular Environmental Science Group at Argonne, we recognized the importance of further developing and organizing the scientific research community that recognized the power of synchrotron radiation for Environmental and Biogeochemical Research.  Following up on a workshop that was held at the Arlie House in 1995, in 1999 we created and organized the first Synchrotron Environmental Science (SES-I) Conference that was held at the APS.  The goal of the conference was to bring together experts in synchrotron radiation and all aspects of Environmental Science so that they could each learn from each other and develop new collaborations.  (Over 100 people attended the conference.)  After we successfully co-organized SES-II in 2002 (over 150 people), the SES Conference series was merged with EnviroSync (a national users organization that promotes the use of synchrotron radiation for Environmental Research) and is now the flagship meeting for EnviroSync that is held every three years at one of the major synchrotrons in North America.