Lamont's Environmental Tracer Group Summer 2001 Lamont Environmental Tracer Group Summer 2001 Research to Photo Essay

For two weeks, scientists from Columbia University have been getting up early and going to bed late to answer this question.

As an experiment, they put a harmless gas into the Hudson River to see how far it would move and how fast it would spread in the water.

On July 25, they injected a small amount of an inert gas, sulfur hexafluoride, 20 feet deep in a small stretch of the Hudson River near Newburgh, N.Y. The gas dissolved and moved, with the river's currents acting like a tracer.

"You get an opportunity to [follow] the real injection of contaminants in water," said Peter Schlosser, chairman and professor of earth and environmental science and engineering at Columbia University.

David Ho, a postdoctoral research scientist, came up with the idea for the experiment two years ago, and this year received funding through the Dibner Fund and the Columbia University Hudson River initiative.

Many of those involved in the project are associated with the Lamont-Doherty Geological Laboratory* in Palisades, N.Y. The laboratory is a division of Columbia University.
* [note: The current name is "Lamont-Doherty Earth Observatory."]

Ted Caplow, a doctoral student at Columbia, and Megan Garrison, a New York City schoolteacher, joined Ho and Schlosser on the project.

"Peter and I thought it would be a good way to examine how the river might respond to human impact," Ho said, explaining their motivation for taking a closer look at the dynamics of the river.

The main goal of the experiment is to understand how water flows in the river and how substances are transported, Schlosser said.

"When most people look at the river, they don't see the continuity," Ho said. "What we do in one spot can affect everyone downstream."

In the past two weeks, the gas has moved a few kilometers a day and has spread over a 30-mile stretch of the river from Poughkeepsie to Stony Point.

Schlosser said he is surprised by the results so far because the high concentration of the gas hasn't moved from Newburgh, the site where it was injected into the Hudson. The experiment has shown that the decrease in concentration of the gas is caused not by the flow of the river but instead by the churning of the river.

"We thought it would be a combination of both, but what we have seen so far is just the mixing," he said.

The Riverkeeper is the boat used for the experiment and measurements that are collected. "It is a research vessel, a patrol boat, a riverkeeper flag, a presence on the water, and now part-classroom," said John Lipscomb, boat captain.

In the front of the boat a pump continuously draws in water and filters it through a gas chromatograph, an instrument that measures the gas concentration.

It measures the water to see if the gas has spread.

Onboard the researchers have two laptop computers that control the entire experiment from timing to collecting all the data, Caplow said. The automated systems take up to 300 samples a day.

The experiment, which will be finished early next week, has had its share of problems, from computer glitches to electrical and pump malfunctions.

As the experiment winds down, the researchers say they have gained a new respect for the Hudson River as a system.

"I have learned more about the natural dynamics of the river and what would happen if there was a spread of a pollutant," Caplow said.

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Reproduced with permission of The Record (Bergen County, NJ)
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Lamont Environmental Tracer Group Summer 2001 Research to Photo Essay