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Environmental Chemistry
Research Chemists

John H. Zimmerman - Branch Chief (Acting)

L. Don Betowski, Ph.D.

Georges-Marie Momplaisir, Ph.D.

Christian Daughton

Jade Morgan

Edward M. Heithmar, Ph.D.

Lantis I. Osemwengie, Ph.D.

Mike Hiatt, B.S.

Steven Pyle, M.S.

Tammy Jones-Lepp, M.S.

Charlita Rosal, M.S.




Christian G. Daughton, Ph.D.

Chief, Environmental Chemistry Branch, Environmental Sciences Division, National Exposure Research Laboratory, Office of Research and Development, U.S. EPA, Las Vegas, Nevada.

Ph.D. 1976, University of California Davis: Ecology (Environmental Toxicology)

Thesis: "Parathion and Acclimated Bacteria: Interactions in the Chemostat and in Soil." Advisor: Professor Dennis P.H. Hsieh (Department of Environmental Toxicology).

Research Faculty (U.C. Berkeley) in 1976 and supervisory research scientist at LBL (1980). Federal career begun in 1991 at EPA Las Vegas as Chief of Methods Research Branch.

Supervision of interdisciplinary research (engineers, chemists, microbiologists).
Analytical chemistry, environmental microbiology, environmental toxicology.

Impact of Research:
Pioneering studies on bacterial metabolism/decontamination of organophosphorus pesticide wastes in continuous culture and in soil predated the field of "bioremediation." Elucidated new metabolic pathways during biodegradation of chemical warfare agents (alkyl phosphonates).

Directed interdisciplinary DOE research on environmental fate and control technologies for oil shale retort pollutants.

Currently lead analytical chemistry program at EPA-LV. Focus is on the so-called "emerging," non-regulated chemical pollutants, such as pharmaceuticals and personal care products (PPCPs). Designed and maintain the world's first web site devoted to the many aspects of PPCPs as environmental pollutants (http://epa.gov/nerlesd1/chemistry/pharma/).

Over 35 peer-reviewed publications in the peer-reviewed archival literature.

L. Don Betowski, Ph.D.
Research Chemist

Ph.D. 1974 - Cornell University: Physical Chemistry

B.S. - 1966 - Georgetown:  Chemistry

Thesis: "The Applications of Chemical Ionization Mass Spectrometry to Inorganic Systems." Advisor: Professor Richard Porter.

Federal career begun in 1979 at EPA Athens

Research in mass spectrometry and hyphenated MS techniques
Computational chemistry for methods development and chemical property prediction
Textile dye analysis

Impact of research:
Pioneered adoption of capillary-GC/MS and LC/MS/MS at EPA
Pioneered use of computational chemistry for environmental analytical chemistry

39 peer reviewed journal publications and 7 book chapters

Edward M. Heithmar, Ph.D.
Research Chemist

Ph.D. 1978, University of Pittsburgh: Analytical Chemistry

Thesis: "Continuum Source Atomic Fluorescence of Arsenic." Advisor: F. W. Plankey

Career begun in 1978 at University of New Orleans as Assistant Professor of Chemistry

Joined EPA in 1978 as GS-12 Research Chemist

Atomic mass and optical spectrometry (ICPMS, AFS, AAS)
Elemental speciation

Impact of research:
Improved exposure assessments through elemental speciation
Enhanced ICPMS measurements through on-line preconcentration

18 peer reviewed publications

Mike Hiatt, B.S.
Research Chemist

B.S. 1969, University Nevada, Las Vegas: Chemistry
B.S. 1969, University Nevada, Las Vegas:  Physics

Career begun at Bureau of Mines. Transferred to EPA/ORD as radiation chemist and organic chemist. Joined private sector and advanced to Laboratory Director of environmental laboratory.  Rejoined EPA in 1989.

Laboratory management and quality assurance research

Impact of research:
Two RCRA SW-846 methods involving a new analytical technique.  Two patents and license agreements of commercialize patents.

13 peer-reviewed publications

Tammy Jones-Lepp, M.S.
Research Chemist

M.S. 1992, University of Nevada - Las Vegas, Las Vegas, NV

Thesis: "The Detection and Evaluation of Fluorescent Brighteners As Organic Tracers in Alkaline Groundwaters." Advisor: Klaus J. Stetzenbach, Ph.D.

Career begun in 1978 at EPA as GS-2 (EPA/ORD Las Vegas)

Research using mass spectrometry (MS, MS/MS, ion trap) and various liquid chromatographic interfaces (thermospray, electrospray). Research using microseparation techniques (CE, -LC). Application of research to detection of organotins and pharmaceuticals in environmental matrices.

Impact of research:
Reduce sample analysis time and cost; reduce laboratory-generated pollution. New regulations regarding organotins in drinking water, Contaminant Candidate List (CCL) as published in the Federal Register (Monday, March 2, 1998 Part III Environmental Protection Agency, Announcement of the Drinking water Contaminant Candidate Listing Notice, vol. 63, no. 40, pg 10282).

Over 20 peer-reviewed publications/book chapters.

Active within Las Vegas public school system (classroom science demonstrations, science fairs, career development)

Georges-Marie Momplaisir
Research Chemist

Ph.D. 1996, McGill University: Analytical/Organometallic Chemistry

Thesis: “Development of Analytical Methods for the Speciation of Arsenic in the Marine Environment.” Advisor: Professor William D. Marshall.
(Department of Food Science and Agricultural Chemistry)

Career began in December 1995 as a Post-Doctoral Research Associate of the U.S. National Research Council. The research work was conducted at the Environmental Chemistry Branch of the U.S. EPA, Las Vegas and was completed in December 1998.

Worked as a Research Chemist and Laboratory Coordinator for the Harry Reid Center of Environmental Studies, University of Nevada, Las Vegas, from December 1998 to April 1999.

Joined the Environmental Chemistry Branch of the U.S. EPA, Las Vegas as a Research Chemist in April 1999.

Determination of trace elements using hyphenated techniques (HPLC-UV, HPLC-THG-AAS, HPLC-ICP/MS, HPLC-ES/MS and HG-AAS).
Analysis of ultra-trace levels of agricultural pesticides.

Impact of research:
Provided reliable and sensitive analytical tools to speciate trace element contaminants in complex matrices.
Made available analytical procedures to isolate, concentrate and purify ultra-trace levels of agricultural pesticides in large volumes of water.

10 peer-reviewed journal publications.

Analytical chemist with an expertise in trace element speciation. Research interests are in the field of environmental chemistry and fate of trace elements. Current research thrusts are directed to trace arsenic and selenium speciation in biological materials, and determination of agricultural pesticides in environmental samples. Methods have been developed for the speciation of arsenic and selenium in environmental/biological media and for the determination of ultra-trace levels of agricultural pesticides in large volume of water.

Lantis I. Osemwengie, Ph.D.
Research Chemist

Ph.D. 2002, University of Nevada, Las Vegas: Environmental Science (Chemistry Track)

M.S. 1984, Prairie View A & M University, The Texas A & M University System: Soil Science

B.S. 1982, Texas Southern University: Major: Chemistry. Minor: Mathematics

Dissertation: "Levels of Synthetic Musks in Municipal Wastewater for Estimating Biota Exposure in Receiving Waters." Advisor: Professor Shawn Gerstenberger.

Masters Thesis: "Accumulation of soil Ni in Leaves and Tubers of Radish and Turnip." Advisor: Professor Eugene Brams.

Career began in 1985 at University of Benin, Nigeria as Assistant Lecturer of Soil Chemistry, under Professor Egharevba. Joined New York City Department of Environmental Protection, Special Project Laboratory in 1992 as Assistant Chemist. Moved to U.S. EPA (ORD, Las Vegas) in 1999 to the present position.

Trace organic analysis, using GC/MS, GC/ECD, GC/NPD, GC/FID, and HPLC instrumentation.
Development of alternative methods for collection of environmental samples, extractions, cleanup techniques, and identification of previously unknown contaminants in various environmental compartments. These include pharmaceutical and personal care products (PPCPs), polychlorinated biphenyls (PCBs) and polychlorinated terphenyls (PCTs).

Impact of research:
Dramatic reduction in analytical uncertainty with regard to false negatives and false positives. The methodology developed from this research project will greatly reduce detection limits for PCBs, PCTs, PPCPs, and other trace pollutants by allowing permitting sample sizes of 50 liters or more as opposed to the conventional limitation of one liter. This increases the chances of detecting analytes that would otherwise escape detection (false negative).
Researchers' use and exposure to hazardous solvent are drastically reduced.
Labor costs are reduced.
Research on levels of synthetic musks in municipal wastewater can provide estimates of potential contamination of the downstream aquatic environment and associated biota. Human exposure to xenobiotics or health assessment can be performed based on quality data obtained from this research.

Steven Pyle, M.S.
Research Chemist

M.S. 1978, Xavier University, Cincinnati: Organic Chemistry

Thesis: "Attempted Separation and Characterization on Enzymes Produced by B. macerans." Advisor: Prof. Harvey Dube

Federal career begun in 1976 at EPA as GS-7 (EPA/ORD Cincinnati)

Research using mass spectrometry (ion traps, NCI/CI, MS/MS)
Minimizing sample preparation (SFE, ASE, DAI)
Fast techniques for target analyte screening (DAI)

Impact of research:
Reduce sample analysis time and cost
Reduce laboratory-generated pollution
Assistance to Regional RPMs and instrument manufacturers

15 peer reviewed publications

Charlita Rosal, M.S.
Research Environmental Scientist

M.S. 1992, University of Nevada, Las Vegas: Environmental Analytical Chemistry

Thesis: Determination of Polonium-210 in Lake Mead Fish.

M.S. (ABT) 1980-1982. University of the Philippines, Diliman, Quezon City: Chemical/Environmental Engineering

B.S. 1979. Mindanao State University, Philippines: Chemical Engineering

Ultra-trace pesticide determination using programmable temperature vaporizer (PTV) capillary GC/MS by pulsed-splitless and large-volume injection of sample analytes.

Sample preparation of environmental and biological samples by microwave and block digestion for multi-elemental analysis by inductively coupled plasma mass spectrometry (ICP/MS).

Sample introduction techniques for ICP/MS. Elemental speciation of organometallics by CE/UV and CE-ICP/MS.

Impact of Research
Conventional sample introduction for GC/MS analysis of organics uses 1-uL sample volume. Sometimes, the level of pollutants is very low that even with sample preconcentration (via extraction of a large volume of sample and condensation of extract down to less than 1 mL), detection is not possible. Increasing analyte load by injecting large volume of extract (e.g., 20 uL) enhances sensitivity to compensate for the limited detection sensitivity of mass spectrometer. Large-volume injection (LVI)-GC/MS is useful in exposure assessment of sensitive ecosystems and baseline monitoring of pristine environments.

Because of the different levels of toxicity each species exhibits, elemental speciation is critical in assessing risk for a more sensible and cost-effective clean-up goals. CE-ICP/MS is a technique that provides excellent resolution and sensitivity while utilizing a very small-size sample volume (nL) for analysis so that sample collection and transport are minimized, thus saving cost and time. Most of all, the technique is “green” (generating very low amounts of wastes) which responds to EPA’s mission of pollution prevention.



Environmental Sciences | Research & Development
National Exposure Research Laboratory
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