June 9, 2003

Student's path to graduate school began with undergraduate research project on drinking water contamination

By Shawna Williams

Two years ago, when testers detected a notorious form of the metal chromium in Santa Cruz County's Aromas Red Sands aquifer, residents whose drinking water comes from the aquifer faced urgent questions. Would the chromium make them sick? And where was it coming from?

The 2000 film Erin Brockovich, starring Julia Roberts, was based on a case involving drinking water contamination from industrial sources of chromium; the resulting legal battle ended in a $333 million award for the plaintiffs. One form of the metal, chromium-6, has been shown to cause cancer when inhaled. No studies have found that chromium-6 causes any ill effects when ingested, however, so both the movie and the legal case provoked controversy.

The movie probably contributed to the publicity and the panic surrounding the findings in Santa Cruz County. Ana Gonzalez, then a senior at UCSC, and her thesis adviser, environmental toxicology professor Russell Flegal, decided to take a closer look at the situation. Their first question was a basic one: Were the test results real? Or had the testers accidentally introduced contamination of their own?

Answering this was a tough thesis project for an undergraduate to tackle, but Gonzalez did so with gusto. Now a first-year graduate student in Flegal's lab, she continues to investigate the sources of chromium contamination in drinking water.

Flegal runs one of the world's leading labs for detecting trace elements in water. Much of the lab's work focuses on toxic trace metals such as lead and mercury and their effects on aquatic life in local bodies of water, such as San Francisco Bay.

When measuring concentrations of trace elements in the parts per billion range, avoiding contamination is key. Flegal's lab employs a variety of techniques to ensure the accuracy of results. For example, much of the testing equipment is coated with teflon to prevent metals from leeching into a sample, and all equipment is washed in acid before use to remove potential contaminants.

Flegal's lab had not studied chromium levels in groundwater before, so Gonzalez had to find out which techniques would work for measuring chromium, and set up all of the sampling equipment.

"She had to set up the sampling system and the analytical system--these are things that can take years to do, and she did it in a matter of months," Flegal said.

Gonzalez received valuable guidance from postdoctoral fellow Kuria Ndung'u, who had designed a new separation method for chromium for his doctoral dissertation at Lund University, Sweden. An important component of the analysis was separating chromium-3, a positively charged form of chromium, from chromium-6, its negatively charged counterpart.

"Chromium-3 is a trace nutrient, and it's thought that your body needs a little bit of it, but chromium-6 is carcinogenic when it's inhaled, so it's sometimes referred to as the bad chromium," Gonzalez said.

Gonzalez sampled 23 sites for the project, used a filtering system to separate the chromium-6 from the chromium-3, and measured the levels of each. Her findings confirmed that most of the chromium in the groundwater she sampled is chromium-6, but that the levels are well below California's current maximum contaminant level for the metal. She also found clues to the source of the chromium-6.

"If it was a man-made contaminant, you'd expect to find an even spread of chromium, with the highest level near where the chromium was seeping into the water," Gonzalez said. "But what we found is that it's sporadic throughout the sampling area, and so we think it's from a natural source."

A later assessment done by consultants hired by the water district confirmed that the chromium-6 in the Aromas Red Sands aquifer is naturally occurring. Chromium-3 occurs naturally in some rocks, and as the rocks weather the metal ends up in the soil. Under certain chemical conditions, chromium-3 in the soil can turn into chromium-6 and dissolve in water.

Gonzalez's thesis project won the Dean's and Chancellor's Awards for undergraduate research in 2002. She also presented her research at a poster symposium at UC Riverside sponsored by the California Alliance for Minority Participation, and won the award for best poster in physical and engineering sciences.

But Gonzalez didn't stop there. She chose to stay at UCSC to earn a master's degree in environmental toxicology, and is now testing local soil samples to see under what circumstances they might leech chromium-6 into the groundwater.

Ultimately, Gonzalez hopes to use what she learns to describe how chromium behaves in an aquifer. Using equations to describe the chemical interactions that favor one form of chromium over another, she hopes to build an analytical model of the Aromas Red Sands aquifer that can be used to predict where chromium-6 is likely to occur in the aquifer. The same approach could be applied to other aquifers with naturally occurring chromium.

"Ana's project will help us come up with ways to make our water safer," Flegal said. "Chromium is a problem in California because a lot of the rocks here have high levels of chromium in them--natural chromium. So it's important to determine not only if you're getting contamination, but also whether it's from a natural source."

Gonzalez will study not only the factors that lead to the presence of chromium-6 in water, but also under what conditions it might be changed back to chromium-3. This will be especially relevant if lawmakers set a new, lower limit for chromium-6 in water, an idea now under consideration. Gonzalez thinks one option for lowering chromium-6 levels might be to draw drinking water from areas in aquifers where conditions favor the benign form of the metal.

"It's really difficult to study a groundwater system, because there are so many variables," she said. "But I feel that what I'm doing will be enough to get an idea of what is happening in the Aromas Red Sands aquifer."

In the meantime, Gonzalez will spend a month this summer working as a teaching assistant in UCSC's COSMOS program. The residential program is designed for top California high school students with an interest in math, science, or engineering.

"We're going to teach them some tricks of the trade and take them out to do some water sampling," she said. "We want it to be a positive experience for everyone, and one that will make them want to go to college."

In Gonzalez's case, the decision to attend college wasn't an obvious one. She and her twin sister are the only members of her family to do so thus far. The daughter of Guatemalan immigrants, Gonzalez was tempted to stay near her family in Los Angeles--until she visited Santa Cruz.

"I liked the programs and the atmosphere. Everyone is helpful and the environment is beautiful here," she said.

Although she came to Santa Cruz intending to major in biology, Gonzalez ended up with a double major in environmental studies and Earth sciences, combining a solid grounding in science with an understanding of the social and policy aspects of environmental issues.

If all goes as planned, Gonzalez will get her master's degree in environmental toxicology next year. In the long run, she would like a job that involves facilitating communication between scientists and policy makers.

This article is part of Profiles in Excellence, an ongoing series highlighting the outstanding educational opportunities and achievements of UCSC students and graduates. Other profiles are posted on the Profiles in Excellence web page.

Return to Front Page