We can tell a lot about land use from what we find in colloids from water samples. Agricultural run-off, mine drainage – it all shows up there.

Ellen Herman

Professor Ellen Herman, geology & environmental geosciences, describes herself as a hydrologist who studies karst – underground water systems characterized by sinkholes, caves and springs. "Bucknell is a great place for this because so much of the region is made up of limestone and dolomite," she says.

Herman and her students take water samples from local springs in search of colloids – tiny electrically charged particles to which contaminants and bacteria adhere. "We can tell a lot about land use from what we find in the colloids," she says. "Agricultural run-off, mine drainage – it all shows up there."

How quickly a spring's chemistry changes during a storm and shifts back to normal afterward provides another clue to its structure. Herman and a team from Temple University are studying this phenomenon, known as hysteresis. She explains that although automatic sampling mechanisms are in place, chemical changes happen so fast that she and her students often have to take water samples under dramatic weather conditions, garnering quizzical looks from local Amish farmers. "I'm sure they think we're just a little crazy," she says.

Another of Herman's projects involves contaminants that don't dissolve easily in water. Some, like gasoline, are light enough to float; others, such as degreasers, are heavy and settle to the bottom. Either way, these non-aqueous substances become trapped in the karst and are extremely difficult to capture and study. Herman and Professor Rob Jacob, geology, and their students are working with a team from West Virginia University to develop hydrogel beads that will behave just like the contaminants but with the ability to be traced through a karst system and to return data.

How do you know if you're standing on top of a karst system? One of Herman's students is tackling that very problem using resistivity and gravity methods. "We hope to soon be able to map multiple levels of caves from the surface," Herman says.

Posted Sept. 22, 2014