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Chapter 8. Environmental Chemistry

John Birks

Ferguson and Lineberger saw CIRES as a potential vehicle for additional growth in the area of fundamental physical chemistry as applied to the atmosphere, and in 1975 A. W. (Will) Castleman was recruited from Brookhaven National Laboratory as the first chemistry fellow of CIRES. This new faculty position was rostered in the Graduate School at the professor level. Castleman established a laboratory on the first floor of Research Building 1 (later renamed the Litman Research Laboratory (RL-1)) on east campus and a second laboratory in the sub-basement of the Ekeley Chemistry building. He attracted a large group of graduate students and postdoctoral scientists working in the general area of the physical chemistry of cluster ions and of heterogeneous reactions (reactions occurring at phase interfaces). The work was a combination of fundamental studies where the results had highly important long-term implications but no immediate application, and some problems of then-current atmospheric interest. A major interest was the problem of homogeneous nucleation, i.e., how supersaturated gases condense to form particles.

Castleman left CU to join the Chemistry Department at Pennsylvania State University in 1982. A number of factors, both personal and professional, played a part in his decision to leave Boulder. One important professional factor was the general lack of resources provided through CIRES. The split of his laboratory space between east and main campuses and the need to commute up to several times daily to give lectures, attend committee meetings, etc., also played a role. The attitudes of the respective upper university administration and the state legislature toward higher education and the role of research were other significant factors. Will Castleman continues to be highly successful in research at Penn State and has been elected to the National Academy of Sciences.

John Birks was the second chemist to be appointed as a CIRES fellow. Birks, who had earned his Ph.D. in physical chemistry under the direction of Harold Johnston at U.C. Berkeley, was recruited from the University of Illinois at Urbana-Champaign where he was an assistant professor in the analytical chemistry division. Birks had joined the Illinois faculty in 1974, the same year that Rowland and Molina postulated that continued release of chlorofluorocarbons would cause a future stratospheric ozone depletion. At Illinois, he established a research group to measure rates of chemical reactions key to evaluating this new theory. Early work in his group, especially measurement of the rate coefficient for the formation of chlorine nitrate, captured the attention of Aeronomy Lab scientists, and Birks was encouraged to apply for a new CIRES/Chemistry position rostered in the Graduate School. From the perspective of the Chemistry Department, this new faculty position was the first of two positions promised to Bob Sievers, who had been hired as a Professor in 1975 to build a strong analytical chemistry division.

Six graduate students moved with Birks to CU in the summer of 1977, with lab space provided by CIRES in rl-1. Birks continued his work on gas phase kinetics of stratospheric reactions, and with the encouragement of Sievers, began to expand his research into the field of analytical chemistry where graduate student interest was very strong.

Instrument package for air sampling from profiling platform

Throughout the 1980s research in the Birks group was slowly phased from a focus on laboratory studies of gas-phase reactions to the invention and characterization of sensitive detectors for gas and liquid chromatography based on chemiluminescent and photochemical reactions, with a wide range of atmospheric, environmental and pharmaceutical applications. In the early 1990s Birks began to narrow the focus of his analytical detection work to problems in the measurement of atmospheric species. In 1993 he began a collaboration with Ben Balsley of CIRES in developing vertical profiling capabilities for chemical species in the atmosphere using kites, balloons, and light aircraft. In this collaboration, the Balsley group took responsibility for developing meteorological packages and profiling platforms, and the Birks group developed miniaturized instruments for the measurement of such species as ozone, carbon monoxide and carbon dioxide. The two groups have collaborated in numerous field campaigns to study the problems of oxidant formation and transport in the troposphere and landscape-scale fluxes of carbon dioxide.

Birks has received several national awards for his scientific work, including the Leo Szilard Award of the American Physical Society and Sloan and Guggenheim fellowships. In the year 2000 he was awarded the Hazel Barnes Prize, CU's highest faculty award. In 2002, after 25 years of service to CU, Birks chose to retire from CU at the age of 55.

Robert Sievers became a fellow of CIRES in 1980 when he was recruited to succeed Carl Kisslinger as director (see chapter three). As mentioned earlier, Bob Sievers had been hired into the chemistry department for the purpose of building a strong analytical chemistry division. At that time, CU's only analytical chemist, Harold Walton, was nearing retirement. Sievers was recruited from the Wright-Patterson Air Force Base, where he was a group leader in the Aerospace Research Laboratory. Having written his Ph.D. thesis in the area of inorganic chemistry at the University of Illinois under the mentorship of the distinguished chemist John Bailar, Jr., Sievers made his mark by applying principles of inorganic chemistry to problems in chemical analysis. Some of his major contributions prior to moving to CU included the invention of fluorinated nuclear magnetic resonance shift reagents, the first separation of optical isomers in gas chromatography, and gas chromatographic analysis of the first moon rocks returned to Earth.

Bob Barkley, director of the Central Analytical Laboratory, prepares a sample for the tandem mass spectrometer.

Sievers' work in the area of chemiluminescence detection prompted him to co-found Sievers Research with Misha Plam, a Russian immigrant who had served as director of CU's Mountain Research Station. This successful company, which manufactures the Sulfur Chemiluminescence Detector® and a total organic carbon analyzer used in the semiconductor industry and on the Space Station, was acquired by Ionics, Inc. in 1996.

In the 1980s, Sievers became interested in the use of supercritical fluids in analytical separations and for environmental cleanup. This work led to his current focus on the use of supercritical CO₂ for production of small aerosol particles, with a strong emphasis on drug delivery by inhalation.

With more than 30 patents, many of which have been licensed, Sievers has led CIRES in the development of intellectual property. He has received a number of national and international awards for his work, including the Tswett Chromatography Medal and the Keene P. Dimick Award.

The faculty position vacated by Will Castleman was filled at the level of assistant professor by Bruce Koel in 1983. Koel earned his Ph.D. under the mentorship of Mike White at the University of Texas. This was followed by a postdoctoral appointment as a Miller Fellow with Gabor Somorjai at U.C., Berkeley. In CIRES, Koel established an experimental program that used ultrahigh vacuum techniques to study chemical reactions at metal and metal oxide surfaces. The goal of this work was to obtain an improved fundamental understanding of chemical catalysis.

Koel was promoted to Associate Professor with tenure in 1989. Some of his research at CU focused on elucidating the mechanism by which oxides of nitrogen react with carbon monoxide at a gold surface in the NOy (total reactive oxides of nitrogen) detector developed in the Aeronomy Lab by Mark Bollinger (graduate student), David Fahey (then a postdoctoral scientist), Fred Fehsenfeld, and Bob Sievers. Recently, this detector was used by Fahey on board the er2 aircraft in his discovery of "acid rocks" in the polar stratosphere. Fahey is now a senior scientist in the Aeronomy Laboratory.

Koel left CU in 1990 to join the Chemistry Department at the University of Southern California where he has continued a highly successful career in surface science.

Fred Fehsenfeld was among the first NOAA scientists to be appointed as a CIRES fellow in the Environmental Chemistry and Biology Division. Prior to joining CIRES, Fehsenfeld's early work in the Aeronomy Lab with Eldon Ferguson and Daniel Albritton involved measuring the rates of a very large number of ion-molecule reactions using the flowing afterglow technique developed by the Ferguson group. This work led to a greatly improved fundamental understanding of the thermodynamics and kinetics of this important class of gas-phase chemical reactions. As mentioned earlier, the work also provided a nearly complete understanding of the chemistry of the ionosphere.

In the early 1980s, the Aeronomy Lab, which had until that time concentrated its research on the upper atmosphere, initiated a major research effort in the troposphere. Fehsenfeld became the scientific and programmatic leader of this effort, where over the past three decades he has conducted pioneering research in the area of regional air quality. The leadership he provided for numerous field campaigns has led to a greatly improved understanding of the factors that control ozone levels in the lower atmosphere. These contributions have helped provide a scientific basis for improving air quality and health protection to citizens and for regulation of industrial and automotive emissions.

Fehsenfeld has served on the CIRES Executive Committee and as associate director for Environmental Chemistry and Biology since the mid 1980s. In addition to receiving five outstanding paper awards for his contributions to scientific meetings, he has been awarded the Gold Medal of the Department of Commerce and has been elected a fellow of the American Geophysical Union.

Russell Schnell earned his Ph.D. in Atmospheric Science at the University of Wyoming in 1974. Following postdoctoral research experiences at NCAR and NOAA, he worked for two years in Nairobi, Kenya where he directed a United Nations project studying the feasibility of building a baseline pollution monitoring station on Mount Kenya. In 1979 he joined CIRES as a research scientist, and in 1986 was elected a fellow of CIRES. Schnell's early work at CIRES involved studies of natural ice nucleants, an outgrowth of his Ph.D. work. His work soon expanded to include field studies involving a wide range of atmospheric species, especially aerosols, and constituted some of the first aerosol work in CIRES. A major contribution to the atmospheric community at large was his conception and organization of the Arctic Gas and Aerosol Sampling Program (AGASP). This multinational program involved large field campaigns in 1983, 1986, and 1989 to study the coupled chemistry and meteorology of the Arctic and provided the first thorough characterization of the phenomenon of "arctic haze."

Schnell left CIRES in 1991 to become director of the Mauna Loa Observatory in Hilo, Hawaii. Since 1998 he has been back in Boulder as Director of Observatory Operations in NOAA/CMDL, where he is responsible for operations, budgets, and personnel at all four CMDL remote sampling laboratories (Mauna Loa, Samoa, Barrow, South Pole).

Murray Johnston joined the analytical division of the Chemistry Department as an assistant professor in 1982 to fill the position left vacant by the retirement of Harold Walton. Because of the strong overlap of his research interests with other CIRES fellows, Johnston also was simultaneously appointed as a fellow of CIRES even though his position was not rostered in the Graduate School. Johnston earned his Ph.D. at the University of Wisconsin working in the group of John Wright. This was followed by a postdoctoral position with Rick Van Duyne at Northwestern University. In his research at CU, he combined laser spectroscopy with mass spectrometry for sensitive and selective chemical analysis. In his early work, he was among the first investigators to apply resonant twophoton photoionization to produce ions that were separated by time-of- flight mass spectrometry. He was promoted to associate professor with tenure in 1989. Soon after promotion, however, Johnston was actively recruited by the University of Delaware. After moving to Delaware, Johnston continued a collaboration he had begun with Dan Murphy of the Aeronomy Laboratory. Together, they developed the technique of laser ablation mass spectrometry of single aerosol particles. Over the past few years, laser ablation mass spectrometry has developed into one of the most powerful techniques for field studies of aerosol chemistry, with numerous research groups advancing the instrumentation first developed by Johnston and Murphy. Johnston continues to work in this area at Delaware and to make innovative advances in the coupling of laser spectroscopy with mass spectrometry.

The combined loss of Murray Johnston in 1989 and Bruce Koel in 1990 was a huge setback to the environmental chemistry program of CIRES and Chemistry. Following a postdoctoral appointment in laser spectroscopy with Joel Harris at the University of Utah, Kathy Rowlen, a joint Ph.D. student of John Birks and Jim Avery, was recruited by the Department of Chemistry and Biochemistry to fill the Johnston position. Rowlen's proposed research program did not involve environmental chemistry, and as a result she was not invited to be affiliated with CIRES. Rowlen is now a tenured professor in the analytical division with a strong research program involving molecular orientation at surfaces, design and characterization of nanostructured materials, surface-enhanced Raman spectroscopy and bioanalytical chemistry.

Margaret (Maggie) Tolbert was recruited by CIRES and the Chemistry Department in 1991 to fill the position vacated by Bruce Koel. Following her Ph.D. research at Cal Tech under the direction of Jack Beauchamp, Tolbert worked as a postdoctoral scientist with David Golden at Stanford Research Institute. In 1985, discovery of the Antarctic "ozone hole" was reported by a scientific team lead by Joseph Farman of the British Antarctic Survey. As discussed below, Susan Solomon of the Aeronomy Laboratory hypothesized that the ozone hole was caused by chemical catalysis by chlorine compounds derived from CFCs. The key to this theory was that chlorine nitrate (ClONO₂) must react with hydrochloric acid (HCl) on the surfaces of polar stratospheric cloud particles to form a photochemically reactive form of chlorine, Cl2. However, past work by the Golden group had shown this heterogeneous reaction to be negligibly slow on concentrated sulfuric acid. Tolbert repeated those experiments and found that, in fact, the reactions were fast on ice and could account for the rapid activation of chlorine in the polar spring. The paper describing that work won the AAAS Newcomb Cleveland award for the best paper in the journal Science for 1987-1988 and led to her receiving the 1993 James B. MacElwane Medal of the American Geophysical Union.

Tolbert established her research laboratory in the newly constructed CIRES building on campus. Her research program initially focused on determining the chemical composition and physical state of polar stratospheric cloud particles. This work has expanded to include studies aimed at understanding the mechanism of the formation of cirrus clouds, which have a strong effect on climate. Chemical reactions that occur on mineral dust is another subject she has explored. Her work has also expanded to include aircraft-based studies of stratospheric aerosols in collaborations with Brian Toon of PAOS and David Fahey of the NOAA Aeronomy Laboratory [ About this Lab ] . Other new directions for the Tolbert group include studying the properties of clouds and aerosols in planetary atmospheres such as Mars and Titan. Tolbert received the 2001 Boulder Faculty Assembly Award for Excellence in Research, Scholarly and Creative Work.

Susan Solomon earned her Ph.D. at U.C., Berkeley in 1981 under the joint mentorship of Harold Johnston, her Berkeley advisor, and Ray Roble and Paul Crutzen of NCAR. Her thesis involved developing and applying a two-dimensional computer model to the stratosphere and the problem of transport between the stratosphere and the upper atmosphere. Solomon joined the Aeronomy Lab in 1981 immediately after completing her Ph.D. Early in her career, she co-authored Aeronomy of the Middle Atmosphere with Guy Brasseur, a book which soon became a classic in the field of atmospheric chemistry.

Although Solomon has made many contributions to our understanding of atmospheric chemistry, her explanation of the Antarctic ozone hole and her leadership of expeditions to the Antarctic and Arctic to investigate polar ozone depletion established her as an international leader in all of atmospheric science. Several explanations, both purely meteorological and chemical were proposed for the mysterious ozone hole soon after its discovery was disclosed in 1985 by Joseph Farman. Solomon theorized that ozone depletion was caused by catalysis by chlorine species derived from CFCs. As mentioned earlier, at that time atmospheric chemistry models predicted that virtually all of the chlorine in the lowermost polar stratosphere would be tied up as unreactive chlorine nitrate (ClONO₂) and hydrogen chloride (HCl). Solomon proposed that the ClONO₂ would react with HCl on the surfaces of polar stratospheric cloud particles to form photochemically active chlorine (Cl₂) and nitric acid (HNO₃). The nitric acid would remain in the polar stratospheric cloud, thus "denitrifying" the stratosphere and, in effect, keep the chlorine in a catalytically active form. Such heterogeneous reactions were at that time considered to be unimportant in the stratosphere. However, this key reaction was soon confirmed in the laboratory by Maggie Tolbert and David Golden at Stanford Research Institute, as discussed earlier, and by the research group of Mario Molina. Solomon led two scientific expeditions (National Ozone Expeditions I and II) to the Antarctic in 1986 and 1987, where the key ozone depleting chemicals were detected and quantified. She led a successful effort using visible spectroscopy techniques to measure chlorine dioxide, a molecule whose chemistry had been elucidated in part by the work of John Birks. Chlorine monoxide was also measured by scientists from the State University of New York at Stony Brook, led by Dr. Robert de Zafra. These measurements were among those that proved her theory to be correct. A subsequent expedition led by Solomon to the Arctic in 1988 showed for the first time that the same chlorine-activating reactions occur over the North Pole, suggesting that in very cold years an ozone hole could form in the more populated Northern Hemisphere as well.

Proper interpretation of the Antarctic ozone hole led to a global ban of many CFCs and bromine-containing analogs (Montreal Protocol and subsequent amendments). Prompted by Farman's discovery and Solomon's interpretation of the ozone hole, the 1995 Nobel Prize in Chemistry was awarded to Paul Crutzen, Mario Molina and F. Sherwood Rowland for their early work in predicting the destructive effects of chemical catalysts such as oxides of nitrogen and chlorine species on the ozone layer.

Solomon has worked tirelessly to interpret the science of the ozone hole to government agencies and the public through congressional testimony, serving on numerous national and international committees, and presenting public lectures. Sparked by the interest in Antarctica she acquired through four expeditions there, Solomon recently wrote the popular book The Coldest March, in which she describes the tragic attempt in 1911-1912 of the British team led by Robert Falcon Scott to reach the South Pole.

Solomon was elected as a fellow in 1995 and entered the CIRES Council as our most highly honored scientist. Some of her more significant awards include the James B. MacElwane award of the AGU, Department of Commerce Gold Medal, Henry G. Houghton and Carl-Gustaf Rossby Awards of the American Meteorological Society, Common Wealth Award for Excellence in Science and Invention, Bonfils-Stanton Prize, election to the National Academy of Sciences (at the age of only 36), election to the French Academy of Sciences, R&D Magazine Scientist of the Year, and our nation's highest scientific honor, the National Medal of Science in 2000.

Appointed as a fellow in 2000, Veronica Vaida is the most recent chemist to join the Council of Fellows. A native of Romania, Vaida completed her Ph.D. thesis work in physical chemistry at Yale University in 1977. Following a two-year postdoctoral appointment at Harvard University, she was invited to join the Harvard faculty where she established a research program studying the laser-induced photochemistry of volatile metal complexes. Vaida was recruited to the CU Chemistry Department in 1984 as an associate professor where she extended her research to studies of the photolysis of weakly bound cluster ions. Vaida developed a strong interest in atmospheric chemistry beginning in about 1988 when she and John Birks, just prior to a Chemistry Executive Committee meeting, engaged in a discussion of the possible significance of the atmospheric photochemistry of weakly bound cluster molecules. This discussion led to a joint grant from NSF and eventually a complete shift of Vaida's chemical physics research to applications involving atmospheric chemistry. Vaida also began a collaboration with Susan Solomon on the photophysics of chlorine dioxide photolysis and the measurement of high resolution spectra of atmospheric species for use in modeling and field measurements. Recently, in a collaboration with Adrian Tuck of NOAA and Barney Ellison of the Chemistry Department, Vaida initiated studies of the effects of organic surfactants on the chemistry of aqueous aerosols, such as those found in the marine boundary layer. Vaida, Tuck and Ellison have postulated that surfactants may affect the chemistry and lifetimes of aqueous aerosol particles and have put forward the highly innovative and interesting proposal that particles coated with organic layers might have served as vessels for the origin of life.

Other scientists who served relatively short terms as fellows of CIRES in the Environmental Chemistry and Biology Division include, Richard Gammon, James Avery and Carl Koval. Richard Gammon was a fellow of CIRES during 1982 to 1984 while he served as Chief of the Carbon Dioxide Group within the Geophysical Monitoring for Climate Change (GMCC) laboratory (now CMDL) of NOAA. He left Boulder in 1984 to join the NOAA Pacific and Marine Environmental Laboratory (PMEL) in Seattle.

Jim Avery, a faculty member in the Department of Electrical and Computer Engineering, served as a fellow during 1983 to 1990. Avery was recruited into the Electrical and Computer Engineering Department from the University of Illinois where he had earned his Ph.D. and held the position of assistant professor of chemistry. In addition to his own research program in computer engineering with an emphasis on instrumentation, he has strong collaborations with Susan Avery, currently director of CIRES, in the area of radar remote sensing of atmospheric dynamics. While a fellow of CIRES, he collaborated with John Birks in the development of "whole column detection chromatography." In this collaboration he served as co-advisor to Kathy Rowlen, now a professor in the Department of Chemistry and Biochemistry at CU. In 1990, Jim Avery chose not to renew his appointment as a CIRES fellow. He is currently associate dean for Academic Affairs in the College of Engineering.

Carl Koval, a professor in the Analytical and Environmental Division of the Chemistry department who joined CU in 1980, served as a fellow of CIRES during 1989 to 1991. Koval joined CIRES in the hope of developing a program in condensed-phase (water and soil) environmental chemistry. He served as chair of the Self Study Committee for the 1990 CIRES Program Review. Koval chose not to seek reappointment after only one term, partly because of the lack of progress in developing a nonatmospheric chemistry component of CIRES and partly due to frustrations encountered during the progress of the program review. Koval continues to be an active scientist in the Chemistry department where he recently served as department chair.

Several other CIRES fellows, discussed in other chapters, have made strong contributions to the environmental chemistry program. Especially noteworthy are George Reid, Howard Hanson, Ben Balsley, Ray Fall, Shelley Copley, William Lewis, Carol Wessman, Michael Hardesty, Russell Monson, and Pieter Tans, with research programs spanning such diverse areas as chemical meteorology, environmental biology, carbon cycling, climate change, and remote sensing. It is especially noteworthy that the environmental biology program within CIRES was initiated by atmospheric chemists who chose to recruit scientists that could make the connection between the biosphere and atmosphere. Once in CIRES, those biologists saw the need for a broader-based biology program, a program that includes expertise in the condensed phases of water and soil as well (see chapter nine). The program envisaged is not yet fully developed, but will undoubtedly involve strong interactions with environmental chemists.

Next > Representative Selection of CIRES Publications in Environmental Chemistry

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