MIT/WHOI Joint Program, Marine Chemistry and Geochemistry
Department: Marine Chemistry & Geochemistry
Advisor: Bill Martin and Roger Francois
Research interest: Trace metal biogeochemistry. Linda studies the processes that cycle metals from sediments into the overlying water column.
Expected graduation: 2005
When Linda Kalnejais looks at mud, she doesn't see dull, dirty goo. Yes, it smells, stains her clothes, and blackens her nails. But if you view mud the way she doeswith the eyes of a chemistyou see a dramatic world where tiny, trapped metal toxins can become mud-based menaces.
"It's interesting that something as bland as mud can have these amazing things going on," said Linda, 30, a Joint Program student who studies silver, lead, copper, and other toxic metal pollutants. She wants to know how the toxins are released from the mud into the water. And once they are circulating, she hopes to learn how this changes the water quality.
Since colonial times, muddy sediments in the coastal zoneparticularly in urban waterways near cities like Bostonhave been a gathering place for toxins released from industrial manufacturing, mining, farming, and sewage treatment. More recently, however, stricter local, state, and federal legislation has halted much of the new, direct input of pollution containing toxic metals. This makes contaminated sediments a major source of pollutants to coastal waters.
Chemical reactions are key
Most of the time, the metals that Linda studies bind to the sediments. But chemical reactions, or a disturbance such as erosion or dredging, can release the metals back into the water column. A new sewage treatment plant, for example, may discharge extra organic matter into the coastal zone. The rise in organic matter may trigger chemical reactions that consume oxygen and release metals. Understanding the reactions that occur in the sediments is key to being able to predict the long-term environmental impact of the sewage disposal.
A former water quality engineer in Western Australia, Linda is especially concerned about those toxins that dissolve into the water column. "If phytoplankton come in contact with silver adsorbed to a solid, they will be fine," she said. The dissolved silver can be adsorbed or digested, and can be far more toxic.
Natural resource managers look to work like Linda's to make decisions about how to address pollution. In Boston Harbor, her research could help to guide ongoing cleanup and monitoring efforts, said research oceanographer Michael Bothner with the U.S. Geological Survey in Woods Hole.
"The information Linda provides is useful in deciding how to manage the large inventories of potentially toxic metals found in sediments near coastal urban centers," said Bothner, a collaborator on Linda's project. "Linda's studies help us understand the processes that enable metals like silver, copper, and lead from contaminated sediments to reenter the system and at what rate."
If scientists discover a toxicity problem and understand its behavior, he said, it is easier to suggest a solution to resource managers.
Linda, in cooperation with her advisors and collaborators at WHOI and USGS, has the dirty job of performing the equivalent of mud autopsies on samples collected three times a year from one site in Boston Harbor and another in Massachusetts Bay.
"Mud is up to 98 percent water," Linda said one October evening as she prepared to look at five sediment cores collected that afternoon by divers in Boston's Hull Bay. The rest of it is clay particles, minerals, and organic matter that can all adsorb metals in the mud.
Preparing the samples for chemical analysis requires long hours in wintry conditions. To preserve the integrity of the core samples, Linda works in a "cold room," a noisy, walk-in freezer set to 40 degrees Fahrenheit. She wears a pink and blue knit hat, an extra sweater, and jeans to combat the chill, which she will endure for 10 hours over a Friday night.
She must work quickly. Avoiding disruption of the mud sample is key to good, useable results. The potential for ruin exists in exposure to oxygen and the movement of trapped organisms like worms, wiggling frantically as they realize they have been moved from their watery home.
By 5 a.m. Saturday, she has run sections of the cores through a centrifuge to separate solid from liquid and has filled 192 bottles with water. In the days, weeks, and months ahead, Linda and colleagues will run the water samples through a broad array of analyses. She is particularly interested in seeing how the concentration of metals varies down the length of the sediment cores.
"The results give us a chemistry of the sediments and a snapshot of the overall system," she said.
In addition to sectioning the cores, Linda will also perform a series of experiments to see what happens to the contaminants in the sediments under more dynamic conditions, such as storms. Using an erosion chamber, a whirling machine that mimics real erosion occurring on the coast, she can see what happens to the metals when the mud and toxins become suspended into the water column.
"Storms can move huge quantities of sediments, so it is important to know what happens to the contaminants when this happens," she said.
Linda's interest in science and chemistry was fostered in part by her father, a geologist. "I was always handing him rocks, asking him 'what's this, what's this'?" she recalls. She remembers walks on the beach near her hometown of Perth, where she puzzled over natural processes.
"I would see a pattern of ripples in the sand and wonder how they formed. I'd see a red slick on a rock from groundwater running over it and wonder about the chemical reactions," she said. "I foundand still findso many small events in nature incredibly interesting."
By Amy E. Nevala