Earth Life

For BU researchers, sustainability is more than a one-day event

By Jeremy Schwab

Wally Fulweiler (left), a CAS professor of earth sciences, collecting sediment from Narragansett Bay.

Wally Fulweiler (left), a CAS professor of earth sciences, collecting sediment from Narragansett Bay.

On Earth Day, most people take a moment to think about how their day-to-day choices — food, transportation, housing — affect the environment. At BU, faculty ask those questions every day on a larger scale, examining the impact human beings have on their local environment and exploring new ways to offset that impact.

For Ethan Baxter, a College of Arts & Sciences associate professor of earth sciences, Wally Fulweiler, a CAS assistant professor of earth sciences, and Mark Friedl, a CAS professor and chair of geography and environment, every day is Earth Day.

A rock-solid filter

Baxter’s recent work studying carbon sequestration — the geologic process that filters carbon out of the atmosphere and into rocks — led him to a question that could be critical to reducing global warming: “If we, as a society, cannot stop emitting so much carbon dioxide into the atmosphere, can we take some of it out of the atmosphere?”

Using the department of earth sciences’ state-of-the-art TIMS (thermal ionization mass spectrometer) lab, Baxter seeks the answer. He hopes to use the spectrometer’s high precision isotopic analytical capabilities to date samples of carbonate-rich rocks in order to determine how quickly they formed. He and doctoral student Nora Sullivan (GRS’15) are attempting to date multiple tiny segments of each sample with unprecedented precision. If they succeed, their results will help scientists understand how quickly carbon dioxide could be scrubbed out of the atmosphere.

Meanwhile, researchers in Iceland are pumping large amounts of carbon dioxide into the island’s basalt crust to find out how much of the gas is sequestered by the rock and how quickly it happens. Baxter hopes that by combining the data, he and his colleagues can estimate how much carbon dioxide can be sequestered over the next 100 to 1,000 years — when carbon dioxide levels in the atmosphere are projected to be dangerously high.

The biggest obstacle to developing mass sequestration technology is the amount of carbon dioxide produced to generate the energy to run the machinery — often more than is scrubbed from the atmosphere. Baxter hopes to make the process more efficient by learning what types of rocks sequester carbon most rapidly and effectively, with the aim of eventually placing coal-burning power plants and other industrial emitters near these rock formations, so the carbon dioxide they emit can be pumped underground.

While large-scale carbon sequestration remains a vision, Baxter believes it could contribute to solving the greenhouse problem. “If we can take the carbon dioxide and put it into these rocks, the resulting new rocks won’t break down for millions of years,” he says. “So the carbon dioxide is trapped for a long, long time.”

Too much of a good thing

Human beings aren’t just pumping vast quantities of carbon dioxide into the atmosphere — we also produce huge amounts of nitrogen runoff from fertilizers and human waste. This nitrogen affects both freshwater and saltwater bodies, finding its way into lakes, ponds, rivers, streams, and coastal estuaries.

In coastal saltwater areas, the runoff can lead to massive blooms of phytoplankton, which feed on nitrogen, blocking sunlight from reaching eel grass, a vital breeding ground for fish. In lakes and ponds, dead phytoplankton stimulate bacteria when they fall to the bottom. An overabundance of bacteria can then use up all the oxygen in the water column, creating zones where freshwater fish cannot survive.

Fulweiler literally immerses herself in these dynamic coastal ecosystems. Donning work boots and rubber gloves, she extracts sediment samples to better understand the delicate balance of organisms at the bottom of Narragansett Bay. She tracks the year-to-year balance between two types of bacteria: those that filter nitrogen out of the ecosystem by exuding it as a gas and those that add nitrogen to the ecosystem by metabolizing nitrogen gas. In her recent findings, the nitrogen-adding bacteria actually outdid the other bacteria, creating a net increase of nitrogen from bacterial activity. This, on top of the excess of nitrogen coming in from waste processing plants and farm fertilizers, only adds to the imbalance in the ecosystem.

“We are used to looking at human beings’ impact on the environment in terms of increased carbon dioxide or melting glaciers,” says Fulweiler. “But we are seeing that human activities also affect nutrient cycling, and those are fundamental processes in the ecosystem that deserve more study.”

Taking the pulse of the planet

Naturalists and environmentalists have been tracking seasonal climate changes for centuries — Henry David Thoreau carefully recorded the time spring arrived in his small corner of New England. His records helped Richard Primack, a CAS professor of biology, demonstrate that spring now comes sooner than it did in the mid-19th century, probably because of global warming.

But until recently, scientists could not track seasonal climate changes globally with precision. That’s changed with the advent of satellite-based instruments that measure the amount of leaf coverage in a given location at a given time. As principal investigator for a NASA-funded remote sensing project, Friedl is charged with collecting, analyzing, and making this data available to the public.

“We are, in a sense, measuring the Earth’s heart rate — the seasonal patterns in ecosystem dynamics,” says Friedl. “We are hoping to develop a better understanding so that when we talk about climate change in 10 to 20 years, we will be able to understand the implications of that change for ecosystem function.”

So far, Friedl’s and his team’s findings have confirmed what localized studies have been indicating for some time — spring is indeed coming earlier in the northern hemisphere, and fall is coming later.

This article first appeared in BU Today on April 23, 2009.

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