1. MICROBIAL REDUCTION OF HEXAVALENT CHROMIUM
by Julie McCullough and Art Robinson
(Contact: HYHolman@lbl.gov)

Hexavalent chromium (Cr6+) is a widespread contaminant that enters the environment through various industrial processes. Cr6+ compounds are highly water soluble, toxic in the environment, and carcinogenic in mammals. However, recent studies have shown that certain bacterial species on surfaces of geologic materials can detoxify the compounds by reducing them to relatively insoluble and hence significantly less harmful trivalent chromium (Cr3+) compounds, a process known as biogeochemical transformation. Berkeley Lab scientists have used the Fourier-transform infrared (FTIR) spectromicroscopy beamline (Beamline 1.4.3) at the ALS to obtain spatially resolved, time-dependent spectra that give evidence of the biogeochemical transformation of Cr6+.

This is the first time that biogeochemical transformation of Cr6+ on a mineral surface has been nondestructively monitored and studied. Because infrared light does not kill bacteria, the transformation of Cr6+ can be monitored as it occurs. Distinct and relevant infrared absorption bands related to the transformation are used not only as chemical markers to detect different chromium species, but also as biological markers to detect the presence and activity of microorganisms on specimen surfaces. In addition, the brightness of the infrared radiation from the beamline makes spatially resolved spectroscopy (spectromicroscopy) possible.

Two reduction mechanisms had previously been postulated for the reduction of Cr6+ compounds. The biological mechanism requires the presence of microorganisms to aerobically reduce the Cr6+. The chemical mechanism relies on metal oxides, such as Fe(II) compounds, to catalyze the Cr6+-reduction reaction. The researchers conducted FTIR experiments to distinguish the relative significance of these two mechanisms. In addition, they evaluated the effects of common organic co-contaminants, such as toluene vapor, on the biotic reduction process.

For magnetite surfaces containing no living microorganisms, a five-day exposure to Cr6+ compounds resulted in no statistically significant changes in infrared chemical and biological markers, indicating that no catalysis of Cr6+ reduction was occurring. On samples with living microorganisms, however, some Cr6+ reduction was detected. Moreover, when the samples with living microorganisms were incubated in dilute toluene vapor, statistically significant changes in both infrared-absorption intensity and characteristic band shapes were observed for Cr6+, as were new bands signaling the possible existence of intermediate Cr5+. With FTIR spectromicroscopy, the researchers showed that the changes in the infrared absorption bands occurred at the sites of bacterial concentration. Imaging the surface at characteristic absorption bands showed a strong correlation between peak depletion of Cr6+ and toluene and peak concentration of biological molecules.

In a study to determine if this microbial reduction process could occur in real geologic samples, composite mineral surfaces of basalt rock chips containing resident communities of microbes were exposed to solutions of Cr6+ and toluene vapor. At the end of four months, FTIR spectromicroscopy showed that Cr6+-tolerant and Cr6+-reducing natural microorganisms were thriving in association with Cr3+ (the results can be viewed on the Web at http://www-als.lbl.gov/als/science/sci_archive/bioremed.html). The reduced Cr3+ state was confirmed by x-ray absorption fine structure (XAFS) spectroscopy at Beamline 10.3.2.

The nondestructive infrared spectromicroscopy studies, combined with XAFS spectroscopy and microbiological techniques, show that highly mobile and toxic Cr6+ contaminants can be biologically reduced into less soluble, less toxic Cr3+ compounds. The FTIR method can now be expanded to examine other infrared-amenable microbial/chemical contaminant systems.

Research conducted by H.-Y. N. Holman, D. L. Perry, G. M. Lamble, and J. C. Hunter-Cevera (Berkeley Lab) and M. C. Martin and W. R. McKinney (ALS), using Beamlines 1.4.3 and 10.3.2. Funding: U. S. Department of Energy, Office of Health and Environmental Sciences.

Publication about this experiment: H.-Y. N. Holman et al., Geomicrobiology J. 16(4) (1999), in press.

2. PHYSICAL SCIENCES INDEPENDENT-INVESTIGATOR BEAMTIME ALLOCATED
(Contact: GFKrebs@lbl.gov)

The allocation process for physical sciences independent-investigator beamtime for the running period between October 1999 and May 2000 is complete. The number of proposals was 160, slightly up from the previous period, despite consolidation of the proposals by the scientists. The number of requests for eight-hour shifts increased by about 200. However, only 1,681 shifts, equal to 69% of the total time requested in the proposals, were available. It is regrettable that the ALS will be unable to grant beamtime to many excellent proposals. Competition for time on insertion-device beamlines was especially keen; for these beamlines, the ALS was able to grant only about 55% of the time requested. Those requesting time on the insertion-device beamlines will continue to find the proposal process for independent investigators extremely competitive.

3. CALL FOR ABSTRACTS: 1999 ALS USERS' MEETING
(Contact: alsabstract@lbl.gov)

The ALS Users' Executive Committee (UEC) invites ALS users, including students and postdocs, to submit abstracts for oral or poster presentations at the annual Users' Meeting, to be held at Berkeley Lab on October 18-20, 1999. Highlight oral presentations will be selected by the UEC from the abstracts received; other submissions will be presented as posters. The poster sessions will be held in conjunction with the vendor exhibits on Monday, October 18, 12:00-3:00 p.m., and Tuesday, October 19, 12:00-2:00 p.m.

Please submit a one-page abstract detailing research done at the ALS over the past year. On the bottom of the page, include the name, postal address, email address, phone number, and fax number of the primary author. Please write "student" if applicable and "poster only" if the submission is not to be considered for an oral presentation. [Note: The poster board size is 1.2 m (4 ft) square; push pins will be provided.]

Send abstracts by Friday, August 20, to

Ruth Pepe
Advanced Light Source, MS 6-2100
Berkeley Lab
Berkeley, CA 94720

Phone: (510) 486-5268
Fax: (510) 486-4773
Email: alsabstract@lbl.gov

4. WORKSHOP OFFERS USERS OPPORTUNITY TO DISCUSS BEAMLINE FUTURE
(Contact: ACThompson@lbl.gov)

A diverse group of scientists who use Beamlines 10.3.1 (micro-XRF) and 10.3.2 (micro-XAS) gathered at the ALS on July 30 for an all-day workshop. Al Thompson, of Berkeley Lab's Center for X-Ray Optics (CXRO) and organizer of the event, said the workshop had three goals: to help develop a strong user community, to get user comments on beamline upgrade plans, and to explore new management options for the beamlines.

Originally built by CXRO for the development of x-ray optics, the beamlines have broadened considerably in scope, as reflected in the brief talks given at the workshop by a number of the beamlines' users. Topics ranged from the study of metal impurities in silicon to the time-resolved measurement of aerosols in the atmosphere, and from the detection of trace elements in cancerous lung tissue to the possibility of analyzing future soil samples from Mars for signs of life. Representatives of similar beamlines at the European Synchrotron Radiation Facility (ESRF), the Advanced Photon Source (APS), and Louisiana State University's Center for Advanced Microstructures and Devices (CAMD) also gave presentations about the work being done at their facilities.

At the end of the day, the group was invited to voice their opinions on how best to make the transition from a CXRO-managed facility to one managed by a participating research team (PRT) of core users. Members of a PRT are guaranteed a certain percentage of beamtime in exchange for providing the resources required to operate a beamline. The majority of users preferred to have a single PRT for both beamlines, and a list of interested PRT members was endorsed. Those prospective members will meet soon to begin working out the details of forming a PRT. Users who are interested in being a part of a 10.3 PRT but could not attend the workshop should contact Al Thompson (ACThompson@lbl.gov, 510-486-5590).

5. UEC CORNER
by Stephen Kevan
(Contact: kevan@oregon.uoregon.edu)

Much of this brief message will concern the UEC's recent planning activities for this year's Users' Meeting, scheduled for October 18-20, 1999. The meeting will combine sessions on various specific subjects--magnetic materials and films, environmental materials, chemical dynamics, AMO physics, and biological systems--with other more broadly focused sessions that will include ALS highlights and talks by students and postdocs working at the ALS. The majority of the talks in the focused sessions will be invited, though a few will be added from submitted abstracts. All talks in the highlight sessions will be selected from submitted abstracts. As noted in the call for abstracts above, the abstract deadline is August 20, 1999. The final day of the meeting will be reserved for focused workshops. A few subjects for these workshops have been designated, but more can easily be added if interest exists.

Finally, I want to inform you that ALS Director Daniel Chemla will be giving a talk at a meeting of the Basic Energy Sciences Advisory Committee (BESAC) scheduled for the second week of August. He will primarily provide a status report on changes at the ALS in the wake of the Birgeneau Panel report. The UEC views this as a very important opportunity to communicate with this influential committee. The UEC was asked to have some members attend the meeting to provide, informally, the "user perspective." Nora Berrah and Paul Alivisatos will attend at least part of the meeting for this reason. They also will attend a separate meeting that will include Chemla, DOE program managers, and the head of BESAC. This meeting will focus, in part, on the issue of when or if the BESAC should schedule a follow-up review of the ALS.

These meetings provide an unusual channel for communicating user opinions to the DOE and to one of its high-level advisory committees. As always, I invite you to communicate with me or with any other member of the UEC to convey your opinions in this regard.

6. WHO'S IN TOWN: A SAMPLING OF ALS USERS

To highlight the richness of our user community and help introduce recent arrivals, we offer this listing of some of the experimenters who will be collecting data during the next two weeks at the ALS.

Beamline 1.4.3: Miqin Zhang (Univ. of California, Berkeley, and Berkeley Lab) will study medical implant materials. Mary Kauffman (Idaho National Engineering and Environmental Laboratory) will be investigating the spatial distribution of Burkholderia cepacia G4 attached to basalt and exposed to chemicals. Hoi-Ying Holman (Berkeley Lab) will be monitoring bioremediation activities of certain bacteria on rock surfaces.

Beamline 7.3.1.1: Laurent Seve (Brookhaven National Laboratory) will characterize magnetic nanostructures by photoemission electron microscopy.

Beamline 7.3.3: Roger Falcone's group (Univ. of California, Berkeley) will be doing time-resolved x-ray diffraction from a colossal magnetoresistance crystal.

Beamline 8.0.1: Nicolas Franco, Tony Van Buuren, and Christoph Bostedt (Lawrence Livermore National Laboratory) will study photoemission of self-assembled monolayers, and angle-resolved photoemission of permalloy/Ni(100).

Beamline 9.3.1: Linda Sapochak (Univ. of Nevada, Las Vegas) will use x-ray spectroscopy to study organic electroluminescent metal quinolates. Heinz Frei (Berkeley Lab) will conduct XAFS studies of bifunctional transition-metal molecular sieves for artificial photosynthesis.

7. OPERATIONS UPDATE
(Contact: RMMiller@lbl.gov)

Beam reliability for user shifts was 92.0% for June 21 - July 4, 94.7% for July 5 - 18, and 91.3% for July 19 - August 1. Lost time was mainly due to problems associated with the third-harmonic cavities.

Long-term and weekly operations schedules are available on the Web (http://www-als.lbl.gov/als/accelinfo.html). Requests for special operations use of the "scrubbing" shift should be sent to Bob Miller (RMMiller@lbl.gov, x4738) by 1:00 p.m. Friday. The Accelerator Status Hotline at (510) 486-6766 (ext. 6766 from Lab phones) features a recorded message giving up-to-date information on the operational status of the accelerator.