High-Impact Environmental Research ES&T looks at the people, events, and issues that led to the publication of 10 highly cited papers.
K E L LY N S . B E T TS , BRITT E. ERICKSON, AND RACHEL A. PETKEWICH
O
ver the past 35 years, Environmental Science & Technology
has been privileged to print many papers that have signif-
icantly advanced or changed the environmental sciences.
In this article, we look at 10 of those papers, chosen because they were among the most cited according to a citation index. Rather than discuss only the science, which has become well known, we focus on the people, events, and issues that led researchers to their discover-
ies and conclusions. 488 A I ENVIRONMENTAL SCIENCE & TECHNOLOGY / DECEMBER 1, 2001
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Sorting through 209 PCB congeners
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“High-Resolution PCB Analysis: Synthesis and Chromatographic Properties of All 209 PCB Congeners” by Michael D. Mullin and Cynthia M. Pochini, U.S. EPA; Sheila McCrindle and Marjorie Romkes, University of Guelph, Canada; Stephen H. Safe and Lorna M. Safe, Texas A&M University; 1984, 18, 468–476. When Steve Safe, a toxicologist, and Mike Mullin, an analytical chemist, set out to synthesize all 209 polychlorinated biphenyls (PCBs) and determine their gas chromatograph (GC) retention times in the late 1970s, people thought they were a little bit nuts, says Safe. With the help of a couple of summer students and even his wife, Safe eventually did succeed in synthesizing all 209 PCB congeners, and Mullin developed a separation technique for quantifying the individual congeners in mixtures. This work set the stage for characterizing PCBs in commercial mixtures and environmental samples. “It was a natural marriage between the two of us,” recalls Safe. “The only way to estimate the toxicity of a mixture was to know the individual compounds. Mike was doing the separations and I was doing the toxicology and synthesis,” he says. From about 1978 until 1983, Safe and his co-workers busily synthesized PCBs. At the time, researchers were primarily concerned about PCB congeners that exhibit dioxin-like activity, he says. “We had just identified the mono-ortho coplanar PCBs. They are present in fairly high concentrations, and in many cases, they contribute to the dioxin-like toxicity,” he adds. In the interim, without any standards, Mullin and his co-workers had to estimate where the PCB peaks would appear in the chromatogram. “We had some vague ideas. We used [Monsanto’s] Aroclors as an approximation, with half a dozen peaks,” says Mullin. But at best, the analytical techniques back then, which were primarily packed-column GC, were only semiquantitative, he says. With little encouragement from the U.S. EPA, Mullin pushed forward to develop a better analytical technique for quantifying individual PCB congeners. He believed that packed columns would not do the job and moved to capillary GC columns, which had already been used in Europe for a while. “We were really on our own. I wasn’t working with other EPA facilities because at the time they didn’t see the benefit,” he says, referring to how slow EPA was to accept capillary columns. In the end, he finally succeeded in developing a method to separate PCB mixtures using capillary GC and an electron-capture detector. Mullin and Safe are no longer working in the area of PCBs. Mullin is still at EPA’s Large Lakes Research Station in Michigan, but he now studies mercury. Safe remains at Texas A&M, but he has moved more into molecular biology. In particular, he is investigating how estrogen works through the estrogen receptor in breast cancer cells and in animals. His group has
© 2001 American Chemical Society
helped develop new drugs for breast and endometrial cancer. But Safe hasn’t completely forgotten about PCBs. Today, he jokes, “It’s just sort of a hobby. I still make them sometimes, even though I’m not in the field anymore.” —B.E.E.
Particulates and poisons “Trace Elements in Fly Ash: Dependence of Concentration on Particle Size” by Richard Davison, David Natusch, John Wallace, and Charles A. Evans, University of Illinois; 1974, 8, 1107–1113. It would be difficult to overstate the influence that this paper had on air pollution science. The research revealed that the methods previously used to evaluate emissions from coal-fired power plants neglected the largest potential source of health problems: the smallest particles, now well known as PM2.5 and PM10. But it all started as a “fishing trip”, says David Natusch. Before 1975, the pollution emitted by coal-fired power plants was measured based on relatively heavy fly ashwhich is generally larger than 40 µm in diameterthat landed in collection bins after the coal was combusted, explains Natusch. “I set out to see if there was a dependence of trace element concentration on particle size. . . . It didn’t occur to me until I actually found it what the implications were.” Natusch’s group found that the concentration of 10 trace metals, including lead, cadmium, and arsenic, increased markedly with decreasing particle size. The research showed that particles too small to be measured at the time were the ones most likely to contain the trace metals and elements naturally found in coal, explains Natusch. He says that the metals they found on the particle surfaces are well situated to do the most damage to human health because particles of that size are most likely to make it into the deepest part of the lungs, he says. The research team determined that the design of coal-fired power plants unintentionally encourages the trace elements volatilized during the combustion process to recondense on the surface of small particles after they leave the combustion chamber and the temperature cools down, Natusch says. “What we’re saying is that the control systems . . . [were] actually designed to allow through the most dangerous material,” he says, noting that organic compounds also follow a similar pattern, although they weren’t measured in this paper. Charles “Drew” Evans says that the paper marked one of the first uses of spark source mass spectrometry in environmental research. “It was the most sensitive technology across the board,” recalls Evans, who now heads Evans Analytical Group, which is one of the world’s largest independent analytical services organizations. Natusch, who originally came to the United States DECEMBER 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY I 489 A
on a Fulbright fellowship, returned to his native New Zealand in 1981 and became the country’s secretary of energy. Today, he works as a private consultant to the oil and gas industry and aids governments around the world with economic reforms. In fact, none of the paper’s coauthors is currently in academia. John “Jack” Wallace now serves as a quality assurance supervisor at the Ventura County sheriff’s Crime Lab in California, and Richard Davison is currently in the chemical and manufacturing controls department at Pharmacia, a pharmaceutical firm. A quarter-century after the paper was published, Natusch laments that its revelations still have not resulted in technologies for producing power from coal that significantly reduce health risks. He says that this is a problem that he hopes to tackle before he ends his career. —K.S.B.
When colored paper works best “Priority Pollutants I—A Perspective View” by Larry H. Keith, Radian Corp., and William A. Telliard, U.S. EPA; 1979, 13, 416–423. In the mid-1970s, several environmental groups sued the U.S. EPA for not setting limits on industrial wastewater effluents, as required under the Federal Water Pollution Control Act. Through a negotiation process, it was decided that EPA would have to control the discharge of 65 compounds and classes of compounds for 21 industrial categories. But if all of the compounds in each of the classes were considered, that list of so-called toxic pollutants would include thousands of compounds. Realizing that it would be impractical for industry to monitor so many compounds, the agency decided to prioritize which compounds to control. With virtually no toxicological data upon which to to base their decisions, the process was daunting. The number of times the list changed was unbelievable, recalls Bill Telliard, director of analytical methods for EPA’s Office of Water. “It got so bad that we went to colored paper. We had the blue list, the green list, and so on. At that time, of course, faxing didn’t work real well in color. So in the corner of the page it would say yellow or green, or whatever color,” he says. In the end, after several iterations, EPA decided to regulate 129 wastewater pollutants. The decision had a lot to do with the availability of analytical standards, how much of a compound was manufactured, and in how many locations the compound was found, says Telliard. The agency decided to call these regulatory compounds priority pollutants rather than toxic pollutants because of the lack of toxicological data, he adds. Of the 129 priority pollutants, only a handful, including the metals, pesticides, and cyanide, had routine analytical methods. “Most of the methods for organics were gas chromatography (GC) back then, so you’d end up having all these different GC runs with different detectors,” says Telliard. “At that time, 490 A I ENVIRONMENTAL SCIENCE & TECHNOLOGY / DECEMBER 1, 2001
mass spectrometry (MS) was not what you would call a routine laboratory procedure,” he says. Drawing on methods for the semivolatile organic compounds developed by co-author Larry Keith and his colleagues at EPA’s Office of Research and Development (ORD) in Athens, GA, and purge-and-trap methods for the volatile organic compounds coming out of ORD in EPA’s Cincinnati laboratory, GC/MS looked like the only promising technique for monitoring the organic priority pollutants, says Telliard. GC/MS allowed large numbers of samples to be analyzed for numerous individual organic compounds relatively quickly and economically, explains Keith, who at the time was managing the chemistry division at Radian Corp. Then there was the question of where to set the limits for these pollutants, says Keith. For the most part, it came down to method detection limits. “We decided that not all, but most organics could be reasonably analyzed by GC/MS at the 10-ppb level in water. When you look at today’s regulations, not all, but most of them are still regulated at that level,” he says. A few of the priority pollutants have since been delisted by EPA, because “they probably had never been looked at by a chemist,” says Keith, who is currently an environmental consultant for Instant Reference Sources. For example, bischloromethylether was put on the initial list, but it hydrolyzes very fast in water. Nevertheless, says Telliard, EPA is still monitoring most of the pollutants. “In addition, we have added a number of other analytes that have come from other EPA offices,” says Telliard. Today, roughly 415 analytes are now analyzed at any given industrial facility, he adds. —B.E.E.
Connecting dead fish with the Olympics “Trimmed Spearman-Karber Method for Estimating Median Lethal Concentrations in Toxicity Bioassays” by Robert V. Thurston, Rosemarie Russo, and Martin Hamilton, Montana State University-Bozeman; 1977, 11, 714–719. Dead fish and Olympic athletes may not appear to have much in common. But the method described in this paper for estimating the point at which a toxic chemical kills 50% of the fish exposed to it owes a debt to sports like gymnastics, diving, and ice-skating. Back in the mid-1970s, when Robert Vance Thurston and his colleagues began the research that culminated in this paper, the U.S. EPA was in the process of establishing quantitative criteria for describing the qualities that freshwater must have to protect aquatic life, data that would play an important role in 1977’s Clean Water Act. Much of the team’s research took place in 1976, which was an Olympic year. The agency was beginning to accumulate “massive amounts of data on fishes,” recalls Thurston, who then, as now, was a research professor in Montana State University’s Fisheries Bioassay Laboratory. He says the agency was particularly interested in devel-
oping acute toxicity tests for aquatic life to help prioritize which pollutants were in greatest need of regulation. The agency’s tests were meant to determine what concentration of a toxic chemical would kill half of the exposed fish in 96 hours. Although the agency had developed good tests for making these determinations, the statistical analysis tools available at that time “left something to be desired”, remembers Rosemarie Russo, who now directs the Ecosystems Research Division of EPA’s National Exposure Research Laboratory in Athens, GA. “No one method seemed to satisfy the data coming out of all tests,” explains Thurston. The probit, logit, and moving boundary methods then in use all had deficiencies, he says. Thurston and Russo credit the paper’s third author, statistician Martin Hamilton, with pulling the research together. Hamilton had never tackled such a problem before, Thurston recalls: “We kept providing him with data, and he kept giving us feedback.” The method that the team ultimately devised after months of data analysis is based on the classic Spearman−Karber method, which Hamilton stresses was decades-old even back in the 1970s. The “trimming” component is what sets apart the new method. It occurred to Hamilton that the practice of trimming scores by discounting the highest and lowest marks conferred by Olympic judges could also serve for counting dead fish. And trimming the data outliers in dead fish counts indeed did the trickthe method proved able to consistently compare data from different tests. Not long after the paper was published, the method for determining acute aquatic toxicity was accepted by the U.S. EPA and quickly gained widespread popularity. Although Thurston says that he hardly considers the paper a seminal work, the method is still in use today. In fact, instructions for using the method can be found on a Web site maintained by EPA’s Center for Exposure Assessment Modeling (www.epa.gov/ceampubl/lc50.htm), which is under Russo’s purview. The paper continues to be popular, according to Russo, who says the method was downloaded 383 times in fiscal year 2001. —K.S.B.
Metal ion adsorption “Effect of Adsorbed Complexing Ligands on Trace Metal Uptake by Hydrous Oxides” by James A. Davis and James O. Leckie, Stanford University; 1 9 7 8 , 12, 1309–1315. By the mid-1970s, it was well known that trace metals are concentrated in aquatic sediments. Adsorption processes were known to have a role in trace metal uptake by sediments, but without spectroscopic probes for examining the surfaces directly, it was difficult to confirm exactly what chemical processes were going on. There was reason to believe that adsorption of organic matter would significantly affect trace metal uptake, but until the publication
of this paper, no one really knew what role organic ligands would play. “The whole issue of attachment and surface speciation was fairly speculative because most of the inferences had to be drawn from changes in bulk solution composition,” says Jim Leckie. Researchers were just beginning to consider metal ion adsorption as a chemical reaction rather than a physical phenomenon, recalls Jim Davis, now an aquatic geochemist at the U.S. Geological Survey in Menlo Park, CA, but at the time, a doctoral student in Leckie’s laboratory. “That opened up the idea that you could thermodynamically model surface complexation reactions,” he says. When Davis began his graduate studies, much work had already been done to understand metal– ligand complexation in aqueous solutions, but little was known about surface complexation reactions. Although trace metal adsorption was fairly well understood, few studies had investigated adsorption of complexing ligands. As part of his Ph.D. work, Davis set out to determine the role of complexing ligands on trace metal uptake by amorphous iron oxide. “As a student, one of my strongest contributions to the paper was in selecting the complexing ligands that we considered,” says Davis. Some of the ligands were chosen to mimic the type of functional groups that are characteristic of natural organic matter, adds Leckie. Davis chose compounds like picolinic acid, which contains an aromatic ring with a nitrogen, and 2,3-pyrazinedicarboxylic acid, which contains an aromatic ring with two nitrogens, to see if the same type of functional group in more than one place on the aromatic ring would make a difference in metal ion adsorption. Indeed, it did. In the end, it became clear to Davis and Leckie that if one part of a ligand is attached to the surface and another part faces away from the surface, the ligand will be capable of forming a strong complex on the surface, just as it would in solution. “That made it likely that when humic substances or fulvic acids were adsorbed, there would be complexing ligands facing toward the aqueous phase that were involved in strong metal attachments,” says Davis. “It is now known that humic substances and organic coatings on mineral surfaces are pretty important in binding metal ions in soils and sediments,” says Davis. “Our understanding of natural organic matter is that it contains relatively large complexing ligands compared to the smaller molecules that we studied in 1978,” he adds. Davis has spent his whole career studying metal speciation and adsorption processes. Instead of the pure mineral phases that he worked with in graduate school, he now works primarily with natural materials, such as soils and sediments, and participates in field studies that show how metal transport is affected by adsorption processes. Now, unlike during his graduate school days, spectroscopic tools are widely available to support his findings. Leckie, too, is still somewhat involved in the area of metal adsorption. His group at Stanford is currently examining the role of surface speciation in promotDECEMBER 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY I 491 A
ing or retarding particle aggregation phenomena. The work should help us better understand how to remove trace contaminants from natural systems and engineered processes, he says. —B.E.E.
Slow but steady sorption “Mechanisms of Slow Sorption of Organic Chemicals to Natural Particles” by Joseph Pignatello and Baoshan Xing, Department of Soil and Water, The Connecticut Agricultural Station, New Haven, CT; 1996, 30, 1–11. When Joe Pignatello first realized that the 14C-labeled ethylene dibromide he had introduced to Connecticut tobacco fields was disappearing faster than the ethylene dibromide fumigant that already contaminated the soil after years of farming, he was stumped. Then he realized that biodegradation would only occur if chemicals were available to degrade, not tightly bound to soil particles. After the 14C-labeled ethylene dibromide had been added, organisms in the soil attacked the labeled compound first because they could not easily access the “older”, unlabeled, and sorbed fumigant. The research focus shifted to more fundamental issues. Pignatello, with the help of Baoshan Xing, a new postdoc from the Univesity of Alberta in Canada, and other associates, they would figure out that the sorption process for any contaminant, which ultimately rules biodegradation, was actually slower than expected. “[The] phenomenon [of slow sorption kinetics] . . . goes against the assumption of many people who were working in the field [at the time] that sorption was fast,” says Pignatello. “And as a result of this general finding, a lot of people became interested in [sorption kinetics] because desorption of chemicals from particles can determine [the chemical’s] bioavailability,” he adds. In their 1996 critical review, the researchers pointed out features of slow sorption kinetics that needed more study and presented two diffusion models for describing this phenomenon. “If we know the sorption mechanisms,” explains Xing, “we can develop better models for predicting the fate, transport, and bioavailability of these chemicals in soil . . . [and] may develop more cost-effective cleanup technology.” They also used slow sorption theory to explain why bioremediation processes were always slower than expected. Pignatello believes the article also introduced the “somewhat controversial” concept that “glassy” and “rubberylike” components make organic matter heterogeneous, and sorption processes more complex. Pignatello attributes the paper’s continued popularity to how “sorption/desorption rates [remain] fundamentally important to the physical and biological availability of pollutants in the terrestrial environment under many circumstances.” However, he says that the field is dynamic and new data have appeared 492 A I ENVIRONMENTAL SCIENCE & TECHNOLOGY / DECEMBER 1, 2001
since 1996. Nevertheless, says Pignatello, “People who study the fate and transport of chemicals are [still] struggling to understand how and why chemicals persist for long periods at low concentrations in the soils.” Pignatello still works at the Connecticut Agricultural Station and is also an adjunct professor at Yale University in the Environmental Engineering Program. Xing was offered his current position as an environmental soil chemistry professor at the University of Massachusetts–Amherst in 1995, but he refused to leave Connecticut until 1996 when this work was finished. The two continue to collaborate. “We do have a basic understanding [of sorption mechanisms], but, still, lots more work needs to be done— that’s why I’m still working on these important issues,” explains Xing with enthusiasm. —R.A.P.
A reliable method “Preparative Isolation of Aquatic Humic Substances,” by Earl M. Thurman and Ronald L. Malcolm, U.S. Geological Survey; 1981, 15, 463–466. Earl “Mike” Thurman laughs when he recalls his fears that this paper would never be published because one of the reviewers made such negative comments about it. The research was the basis for Thurman’s doctoral dissertation at the University of Colorado at Boulder, and he took the unusual step of pleading his case with then ES&T editor Russ Christman in hopes of increasing the paper’s chances of making it through review. Christman made it clear that he could not ethically intercede on Thurman’s behalf, but a revised version of the paper ultimately was published. Over the past two decades, Thurman has kept careful track of the paper’s influence; unlike many of the researchers contacted for this article, Thurman is well aware of his paper’s popularity. In fact, he held a party in honor of the paper’s 500th citation this past summer. Ironically, he does not consider it his most important published work. Instead, Thurman credits timing for the fortuitous paper’s continuing citations. Twenty years ago, the important role played by the dissolved organic material known as humic substances in water contamination was becoming evident, but there was no good way to isolate, concentrate, and purify the material, he explains. As others had already reported, humic substances are a source of the methyl groups that cause disinfected chlorinated methanes, such as chloroform, to form when water is treated with chlorine. Humic substances also tend to bind with trace metals and pesticides in the water. The paper continues to be popular because it describes a simple and reliable method based on adsorption and size exclusion chromatography “that worked no matter whatno matter where the sample was from or whether it was from seawater or freshwa-
ter,” says Thurman, who still works for the U.S. Geological Survey, Denver, but has moved to Lawrence, KS, from where the research was conducted. However, his coauthor, co-worker, and mentor Ronald Malcolm died of cancer in 1996. Thurman also attributes the method’s popularity to its easily observable endpoint. “It’s magical to watch . . . it goes from a ‘low-color’ brown to a bright color as the pH changes. It just amazes you,” he explains. When the International Humic Substances Society was established in the early 1980s, Thurman’s method was chosen as a core means of isolating humic material. And it became even more popular later in the decade after EPA began regulating trihalomethanes. The method is still in use, although it has been revised. An added step isolates the hydrophilic component of the humic matter, Thurman explains. Thurman devoted five years to the research that resulted in this paper and companion articles that describe the science underlying the method. “We didn’t hurry,” he stresses. He argues that being more concerned about research than publishing is the key to writing the important papers that really drive science forward. “The citations are telling us what those key papers are,” he says. —K.S.B.
Partition coefficients predict bioconcentration “Partition Coefficient to Measure Bioconcentration Potential of Organic Chemicals in Fish” by W. Brock Neely, Dean R. Branson, and Gary E. Blau, The Dow Chemical Co. (Midland, MI), 1974, 8, 1113–1115. In the early 1970s, scientists were becoming increasingly aware that chemicals like DDT bioconcentrate, but they desperately needed a tool to identify which chemicals would pose this kind of threat. We wanted to “spot another chemical before it becomes a DDT,” recalls Dean Branson. In particular, says W. Brock Neely, environmental chemists were raising questions about bioconcentration and chemical buildup in aquatic organisms. Like many chemical manufacturers, Dow Chemical was facing increasing questions about the environmental dangers of its wide range of products and had formed its own Environmental Testing and Advisory Board. This board defined bioconcentration and biomagnification as the ability of some chemicals to progressively build up higher and higher concentrations as they go up the food chain, and saw that DDT and PCBs were classic examples. Trained as a biochemist, Neely had been working on structure–activity studies as a way to predict the biological activity of a chemical. Could another physical measurement predict bioaccumulation? “[It] seemed like there should be a good correlation between that [octanol−water] partition coefficient and biomagnification, and there was,” says Neely. The partition coefficients were determined as a ratio
of solubility in a surrogate system of n-octanol, the nonpolar solvent that would mimic fish muscle, and water, but they could often be estimated from chemical structure. To the Dow chemists’ delight, the simple procedure followed a direct relationship with measurements of bioconcentration of several chemicals in trout. The researchers used the measured partition values to derive an equation that predicts a bioconcentration factor. “Everything just fit the way it should fit,” says Neely. “That doesn’t happen very often—very straightforward, nothing unexpected, and no surprises.” But the researchers were nonetheless surprised to find out just how influential their work had become. Branson points out that EPA’s Gil Vieth, a reviewer of this paper who strongly supported the findings, would eventually modify the main equation several times for newer chemicals. Branson adds that the same structure–activity relationships are used in many countries to identify chemicals with the greatest potential to be “persistent, bioaccumulative, and toxic” and reduce them under international treaties. Gary Blau served as the biostatistician and engineer on the paper, and in 1998, after 30 years with Dow, moved to Purdue University to teach statistical modeling and risk management. Branson was the expert in pharmacokinetics and measured the bioconcentration factors in trout. When their boss Perry Gerring first approached Branson to work on bioaccumulation, he said he didn’t know anything about fish, but Gerring assured him that “fish are just like rats.” Branson left Dow in 1993 and now manages a product stewardship program for General Electric Plastics in Indiana. Neely retired from Dow in 1986. He and his wife still live in northern Michigan. After some pro bono consulting work with the World Environment Center and teaching at Saginaw Valley State University in Michigan, Neely is now growing apples. He says, “I use pesticides now; I don’t make them.” —R.A.P.
Surpassing partition coefficients “Partition Coefficient and Bioaccumulation of Selected Organic Chemicals” by Cary T. Chiou, Virgil Freed, David Schmedding, and Rodger L. Kohnert, Oregon State University, Corvallis, 1977, 11, 475–478. Cary Chiou can describe the details of his most cited paper as if he had finished writing it this morning rather than almost 25 years ago. That is probably not so surprising because he considers the work “a big building block” to the “most satisfying” part of his career. Chiou readily acknowledges his debt to another popular ES&T paper (Neely et al., this page). In the 1970s, “the merit of octanol–water partition coefficients for assessing the potential for accumulation of organic chemicals into fish was just recognized,” recalls Chiou. On the basis of octanol–water partition coefficients, DECEMBER 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY I 493 A
pharmacologists had established how relatively watersoluble drug chemicals were stored by animal fat tissues, but little was known about the affinities of PCBs, DDT, and other chlorinated compounds in humans and aquatic organisms because these chemicals had very low water solubility. Environmental scientists urgently needed partition coefficient data, but they were only getting widely varying results with indirect liquid chromatography or other calculation methods. “We reasoned that the water solubility of an organic substance is in reality a partition coefficient by itself because the chemical in water at the point of saturation is actually a partition coefficient between its own excess organic phase and water,” Chiou explains. “It became evident that . . . water solubility could be used in place of octanol−water partition coefficients for estimating a chemical’s bioconcentration potential,” he says. The correlation was refined in later ES&T papers and extended to a paper published by Chiou and colleagues in Science in 1979, which won an award 20 years later for presenting a concept that continues to greatly simplify soil studies. The Science paper addressed a related issue, suggesting that uptake of organic chemicals from water to soil organic matter occurs by partition instead of surface adsorption. Coauthor David Schmedding describes Chiou as the “ideas man”, while he and fellow staff researcher Rodger Kohnert assisted in data collection and performed the experiments. Virgil Freed was the distinguished chair of the Department of Agricultural Chemistry at Oregon State University (OSU). Since the publication of the paper, Chiou has moved to the U.S. Geological Survey in Denver, CO, where for the past 18 years he has focused on distinguishing the effects of organic and mineral matter in soil and sediment on contaminant sorption. Schmedding now works with the National Council for Air and Stream Improvement in Corvallis, OR. Kohnert currently is the manager of OSU’s nuclear magnetic resonance facility. Freed died in the late 1990s. —R.A.P.
ALL IMAGES FROM PHOTODISC AND COREL
Challenging authority “Transport of Nonpolar Organic Compounds from Surface Water to Groundwater,” by René Schwarzenbach and John Westall, Swiss Federal Institute for Water Resources and Water Pollution Control (EAWAG); 1981, 15, 1360-1367. The equations that René Schwarzenbach and John Westall published in this paper are well established now, but the two scientistswho were both postdocs in the late 1970s when this project startedfound themselves challenging authority, including some influential scientists, when they first presented their research. At that time, environmental scientists were just beginning to recognize that contaminated surface water could pollute groundwater by filtering through the sediments, but the mechanisms for such pollu-
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tion were poorly understood. They did know that organic compounds, because of their weight, would tend to sink into the riverbed sediments. Some researchers believed that these pollutants would then be sequestered or degraded, but the mechanisms were poorly understood. To fill in the unknowns, the scientists began collecting data on how pollutants behave in subsurface soil. Starting in 1979, Schwarzenbach, the paper’s corresponding author, focused on nonpolar organic compounds, including alkylated and chlorinated benzenes. Westall, whose specialty is physical and inorganic chemistry, only joined the project after an earlier investigation he made with Werner Stumm, who was then EAWAG’s influential director, revealed that inorganic chemicals did not seem to cause pollution problems. Although the results published in the paper deal with laboratory studies, the research underlying the results was conducted both in the laboratory and in the natural environment. The researchers broke new ground by combining laboratory and outdoor research, and they were among the first to use capillary gas chromatography techniques. “This research made us aware of how important it is to combine molecular-level [research] with macroscopic system research,” says Schwarzenbach, who now heads the Institute for Aquatic Sciences and Water Pollution Control at the Swiss Federal Institute of Technology. The debate sparked by Schwarzenbach and Westall’s research centered on their calculations of the linear free-energy relationships relating the natural organic matter−water partition coefficients of the studied compounds to the octanol−water partition constants. The results indicated that the slope of the regression line that could be derived from these calculations was not necessarily equal to one, contradicting a previous report (Water Res. 1979, 13, 241). Moreover, if the slope was greater than one, the sample was more lipophilic than octanol, and for slopes less than one, the reverse was true. This new result led to spirited discussions at the Gordon Conferences on Environmental Sciences−Water in 1980 and 1982, attest Schwarzenbach and Westall. Ultimately, of course, the young scientists’ arguments held sway. “What we attempted to show was that it’s fine if [the slope] is one [for a given compound], but that’s just an accident,” explains Westall, who now chairs Oregon State University’s Department of Chemistry and still collaborates regularly with Schwarzenbach. “We just persisted; we weren’t backing down,” Westall adds. Westall recalls with some amusement that he and Schwarzenbach were not exactly prescient in one aspect of their research, however. Even in the laboratory, the scientists had a very difficult time maintaining their mass balances while conducting the experiments, Westall says. “The microbes crept in and wrecked our experiments,” he remembers. To obtain their “nice, clean abiotic” results, they had to discard test data that hindsight makes clear was pointing to bioremediation, a phenomenon that is currently at the forefront of environmental science. —K.S.B.
