Northwestern professor Kimberly Gray, above, and her students have worked to restore the ecosystems of southeast Chicago. One of her students analyzed the human and ecological health risks associated with boat slips at abandoned steel mills along the Calumet waterway, such as the shuttered Acme Steel Coke Plant in the distance.

Photo by Andrew Campbell

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Engineering Advocacy

A sidestream elevated pool aeration station helps oxygenate water from the Calumet River. Water is lifted 12 to 15 feet then allowed to drop over a series of weirs to create a waterfall and add oxygen to the river, creating a healthier waterway.

Photo by Andrew Campbell

Kimberly Gray was not particularly fond of chemistry in high school and college. Now she loves chemistry, but it took wading in wetlands on the west coast of India in the late 1970s to set her on that path. Once she realized that chemistry made nature tick, even an encounter with a sea snake couldn’t deter her from using chemistry as the basis for a passionate career solving environmental problems.

An associate professor of civil and environmental engineering, Gray has made chemistry the backbone of her research. Learning how to harness light energy to catalyze reactions to attack pollutants, tracing toxic PCBs, or polychlorinated biphenyls, through the food web in the Great Lakes and figuring out how complex wetlands work — all of this falls under Gray’s investigative umbrella.

She seeks to understand how certain chemical reactions influence pollutants in both engineered and natural systems, with an eye toward the development of applications and technologies for the protection of human and ecological health.

Gray (WCAS78) is also a creative educator who strives to keep things interesting for both her students and herself, a collaborator with diverse faculty across the University, a committed mentor to young women starting out in science and engineering, a social advocate helping disadvantaged individuals and communities and a devoted mother who sews Halloween costumes for her two young girls.

No, she doesn’t sleep much.

Cream Floats to the Top

“Being around Kim is very exciting — her ideas just spill out,” says Joseph L. Schofer (GMcC65, 68), professor of civil and environmental engineering, former chair of the department and recently interim dean of the Robert R. McCormick School of Engineering and Applied Science. “The world is better when we have 100 ideas to sort through rather than two. She is such a significant player in civil engineering. Kim stirs everything up so the really cool ideas float to the top — about science education, new energy sources, sustainability, environmental justice. Just look at all she’s doing.”

Gray’s research interests are broad by traditional academic standards, but her knowledge is deep, and there is a theme running through her work. Environmental engineers have often been thought of as “the clean-up guys,” but Gray doesn’t practice environmental engineering that way. By studying environmental phenomena at a molecular level, Gray is contributing fundamental understanding of environmental science that can be used as the groundwork for social and political change.

Because environmental systems are so highly integrated, so is Gray’s research, incorporating biology and physics in addition to chemistry. Her research team includes four undergraduates, eight doctoral students and two postdoctoral fellows.

“My focus is chemistry, and I get to do it in the most interdisciplinary way — environmental science — which is really fun,” says Gray, who received a bachelor of arts degree in biology from Northwestern in 1978. “And there’s a large social, human component to my work that I love. I see humans in a continuum with nature, with other animals and plants and the systems that support them.”

Three years after returning to Northwestern in 1995, this time as a professor, Gray became associate director of the Institute for Environmental Catalysis, which aims to reduce the impact of human activities on the environment through improved understanding and better application of catalysis. (A catalyst activates and increases the rate of chemical reactions without being changed itself.)

To that end, Gray has been studying titanium dioxide — a white pigment that absorbs light and converts it into chemical energy — as a catalyst for removing pollutants from air and water so that they can be recycled. In the process, she is learning why certain forms of the catalyst work better than others.

“I’m looking at the molecular structure and behavior of the charges to understand what makes a material photoactive,” says Gray. “I want to know how the radiant energy is converted into chemical energy and how that drives the pollution degradation process. If we illuminate the material with light, what happens? And what can I do with this photoactive material? Can I use it to clean and reuse water?”

Optimizing the catalytic photoactive material could lead to a robust system for water treatment used both in space and on Earth. Technology that decontaminates water without using a lot of energy would allow astronauts to go to Mars (and back) with a limited water supply and would give clean water to people living with highly degraded water sources.

The catalyst could be used to coat ceramic tiles to reduce odors. It could also be used in air filters to increase the recycling of air in airplane cabins — thereby improving energy efficiency. Or it could be used to reduce carbon dioxide to make a fuel mixture of methane and methanol.

An Eye on Lake Michigan and Wetlands

Another photocatalyst takes up a great deal of Gray’s attention: periphyton, a complex microbial community of algae, microorganisms, bacteria and fungus that, fueled by photosynthesis, forms a mat and attaches to rocks and large plants in aquatic systems. (Think of the green slimy furry stuff found on rocks in streams.)

While titanium dioxide systems don’t look anything like wetland systems, there are surprising parallels — including water reuse applications. Nearly 10 years ago, because she had an analytic tool that could track organic carbons, Gray was called to California to help on a study of artificial wetlands. She learned that wetlands were very effective at improving the organic quality and reducing the amount of nitrate in an aquatic system, but Gray wanted to know why.

She brought this question home to Illinois and is now tackling a major problem originating in the Upper Mississippi River watershed: each spring, nitrate runoff from the country’s agricultural heartland creates a “dead zone,” an oxygen-deprived area that cannot support life, in the Gulf of Mexico. According to the U.S. Environmental Protection Agency, although the Illinois River watershed makes up only 2.3 percent of the Mississippi River Basin, the state contributes 16 percent of the nitrate load reaching the Gulf of Mexico.

She made an unexpected discovery five years ago while working at the Des Plaines River Wetlands Demonstration Project in Lake County, Ill.: periphyton can be a key to producing high rates of denitrification.

“Wetlands are nature’s kidneys,” says Gray, who was named a Presidential Young Investigator by the National Science Foundation in 1991. “We’ve found they can remove 80 to 90 percent of the nitrogen that comes from fertilizers, and it’s all a light-driven catalytic process. The challenge for us is to design systems where natural processes can eliminate the pollutants. We are looking for an ecological solution to a vast regional problem.”

Gray studies various wetlands in the Chicago area, but to get a really close look at periphyton’s molecular activity, she needed to bring the wetlands into the controlled environment of the lab. So Gray built a wetlands system in the basement of the Technological Institute, where she cultivates her own periphyton.

There, she is learning how the microbes organize themselves and cycle materials and energy. With that insight Gray wants to create conditions that help periphyton grow quickly and maximize its ability to remove nitrate and then put those designer wetlands where they are needed.

“Kim has tremendous energy and is doing such high quality work,” says Aaron Packman, associate professor of civil and environmental engineering, who works closely with Gray on wetlands research. “It is extremely unusual for someone to be involved in basic catalysis research and messy wetlands work because they require such different technical knowledge and abilities. Kim is making major contributions to both.”

In addition to nitrate, Gray is busy tracking another pollutant: PCBs in the Great Lakes. Although beautiful, clear and blue on the surface, Lake Michigan harbors PCBs in the sediments found on the lake’s floor. The manufacture of PCBs in the United States stopped in 1977, but the dangerous toxin persists in the environment.

“It’s hard for humans to stay healthy if a lake is really sick,” says Gray. “In Lake Michigan the water is fine, but the sediment and fish are not. Where does the contaminant go when released into the environment? The PCBs are transferred from the sediments and water to the algae and to the little fish and on up the food web to fish that humans eat.” As a result, health advisories have been issued on the consumption of large amounts of popular fish caught in the lake, such as salmon, whitefish and trout.

Gray, who has a joint appointment in the department of chemical and biological engineering, teamed up with two others from that department: associate professor Luís Amaral, an expert in computer-based modeling, and graduate student Carla Ng. (Gray and Amaral are Ng’s co-advisers.) The collaboration weds Gray’s experience with experimental data with Amaral’s theoretical analysis to map Lake Michigan’s aquatic food web and the transfer of PCBs.

The team is charting who eats whom and when. The diets of organisms change with the season and the life cycle of the organism, says Gray. By understanding the big picture of how PCBs travel from species to species, the researchers hope to offer policy-makers tools that can help them pinpoint which areas of the lake to clean up in order to have the greatest impact on human health.

Amaral admires Gray for her ability to put together a team of people with diverse backgrounds and interests and her ease at then seeing where the collaboration takes the research. Ng agrees and says she also appreciates Gray’s willingness to give her some latitude while still keeping a critical eye on the science being done.

“Professor Gray has helped me transfer my thought processes from student to independent researcher,” says Ng. “Though she is, as my adviser, my mentor and guide, she also allows me to explore my research independently enough that I also feel in part that I am her collaborator. We are working on questions that excite us as scientists, but neither of us knows the answers to these questions before we begin.”

Parlez-vous Français?

Gray knows something about independence and curiosity. Now living in Evanston, she is only a handful of miles away from where she was born. (Born in Chicago, she lived in Deerfield, Ill., until she was 9.) But she’s traveled thousands of miles, physically and intellectually, to get where she is today and loved every step of her somewhat unconventional journey.

The oldest of four children, Gray was the only one in her family to go into engineering. (Her father was financial vice president for Jenn-Air Corp. in Indianapolis, and her mother taught first grade at a private school. Her sister, Kathryn L. Gray [WCAS80], and a brother, Thomas E. Gray [WCAS87], also went to Northwestern.) When Gray arrived at Northwestern as a first-year student, she wasn’t sure what to study. She liked art history but was good at math and science.

“As an undergraduate I didn’t know what I wanted to be,” says Gray, who decided on biology after a process of elimination. “I learned that after college.” (And after building a bicycle and riding it from Chicago to Maine and working summers as a porter and a waitress on Amtrak.)

Environmental engineering entered her world because of her desire to travel. She followed former Northwestern professor T.D. Waite to the University of Miami because he offered her the opportunity to study nutrient cycling in mangrove estuaries on the shores of western India, between Bombay and Goa, for a couple of summers. Mangroves are trees that inhabit the muddy shores of tropical regions and act as fish nurseries. (She also did similar nutrient cycling work in Everglades National Park in South Florida.)

“I loved it. I immediately loved it,” says Gray of her work in India. Once, while wading across an estuary, she thought she saw a sea snake, which is poisonous. Gray says she was so scared she picked up the pace and “walked on water” to get across the channel.

“But it was hard to do rigorous science in the outdoors,” says Gray, “so I went back to chemistry, which, I discovered, I was somewhat good at, and it just clicked.”

For five years at the University of Miami she retooled herself as an engineer, taught an undergraduate course and fell in love with teaching. In 1983, after earning a master of science degree in civil engineering, she packed her bags and headed north to Johns Hopkins University in Baltimore to get a doctorate in environmental engineering.

Johns Hopkins was an “intensely intellectual environment but fun and wonderful,” says Gray, who played tambourine in a rock ’n’ roll band called the New Crusty Nostrils and the Naselles. (Their drummer, Jared L. Cohon, is now president of Carnegie Mellon University.) She also had the opportunity to spend a month in France working on her thesis topic, which involved making an inorganic polymer and exploring its use in drinking water treatment. While there, Gray attended a conference in Switzerland and met a fellow environmental chemist named Jean-François Gaillard, who was from the French Alps. (More on him later.)

After defending her thesis and collecting her doctorate, a two-year postdoctoral fellowship in the research and development lab of the company Lyonnaise Des Eaux pulled her back to France. It was unusual at that time, says Gray, for an engineer to take a postdoc instead of a job. She didn’t speak a word of French but felt this was an opportunity — and a challenge — that she couldn’t pass up. So, with her trademark enthusiasm, Gray went for it.

“I would come home at night with such a headache,” remembers Gray of the early days in Paris. “One, because everyone smoked in my office, but two, because they spoke French! Oh, my head would hurt so badly I would have to go to bed at seven o’clock. It was so exhausting. But I loved it. I had such a great time.”

As her two years came to a close, she realized she missed the university atmosphere — especially academic research where you pose a question and go where it leads you. In 1989 the University of Notre Dame offered her a tenure-track position, and Gray took the job. She was one of the first female engineering professors hired by the university. But before she left France, Gray saw Monsieur Gaillard at another conference in Switzerland, and they’ve been together ever since.

After three years of a commuter courtship, they married in France in 1991, and Gaillard took a faculty position at Notre Dame.

As a woman in engineering and a top researcher in her field, Gray did not go unnoticed by other universities. Northwestern recruited Gray, and in 1995 she and Gaillard both accepted positions in the University’s department of civil and environmental engineering. (Like Gray, Gaillard is also an associate professor in the department.) Her circle was complete.

She’s All About Change

In the classroom, Gray doesn’t confine herself to what she knows best.

“Teaching, for me, is a way to learn,” says Gray, who is an advocate of hands-on learning for her students. “I get bored teaching the same course for 10 years. I like it when students ask me a question that I don’t know the answer to. That’s why I enjoy teaching courses outside my discipline.”

Aware of Gray’s work in urban environments (see “Engineering Advocacy”), Henry Binford, an associate professor of history, asked her to teach in environmental studies as part of the School of Continuing Studies’ Master of Arts in Liberal Studies program. One course was on the environmental past, present and future of cities. Next spring she’ll teach another on the changing views of nature. Gray also taught a cross-school initiative course, Urban Neighborhoods: Issues and Action, with Wendy Espeland, an associate professor of sociology. And because Gray was interested in learning about sustainable manufacturing, she taught a course on that, too, to students in the Master of Management & Manufacturing two-year dual-degree program.

But she hasn’t neglected her own department. For the last two years Gray has worked diligently to revise the curriculum at the undergraduate and graduate levels. She’s also revised the environmental science curriculum in the Weinberg College of Arts and Sciences and integrated it with the McCormick School curriculum.

Gray wants to make a difference outside Northwestern, too. Through her outreach, she is working to improve science and math education for younger students.

“The environment is a wonderful teaching tool for science — wetlands are catalysis, photosynthesis is catalysis,” says Gray, who enjoys conducting science experiments at home with her daughters, Elise, 10, and Sophie, 6. (The older child loves math, and the younger loves science.)

Five years ago (and twice since) she led a one-week workshop at Argonne National Laboratory for middle and high school science teachers about teaching hands-on catalysis and how to make the subject exciting for students. On the heels of those experiences, Gray worked with several Chicago-area high school teachers, most recently with Renee DeWald, a chemistry teacher at Evanston Township High School, to develop five educational modules on environmental catalysis to be used in middle and high schools. The modules, which are part of Materials World Modules, an NSF-funded science and technology education program based at Northwestern, are now being tested nationally.

She sighs with relief. The work on the modules, while valuable, was exhausting, says Gray, whose office is always stacked high with papers, books and journals. “It’s not very efficient to do everything I do — the advocacy, the research, the education. You see my office. This is a consequence of that. But you do need to make a contribution.”

And she does.

Megan Fellman is a senior editor in the Department of University Relations. She covers the sciences and engineering for the media relations group.

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