By Ned Rozell
June 24, 2005
The 1976 oil spill that killed more than 40 black spruce trees and almost all the vegetation around them was no accident. Scientists with the Cold Regions Research and Engineering Laboratory dumped the oil on the muskeg in both summer and winter that year to simulate what might happen if the soon-to-be-built trans-Alaska oil pipeline sprung a leak in a black spruce forest underlain by frozen soil, a common environment in Interior Alaska.
Photo by Terry McFadden
"Nearly 25 years after the oil spill, only 10 percent of the oil in mineral soil has been degraded. In the organic layer, 40 percent has degraded," said Garron at a recent chemistry conference in Fairbanks. "If Alaska were in the tropics, a month after the spill there'd be serious changes."
Bacteria in the soil can consume crude oil, but they work better in places where plenty of soil nutrients, water, and warmth exist. Both Garron and Braddock think the Caribou-Poker creeks oil spill area is short of nitrogen and probably limited in oxygen.
While Garron was studying the site in the summer of 2004, a wildfire swept through. Still, the circa-1976 crude survived.
"The hydrocarbon chemistry hasn't changed much after the burn," Braddock said. "There's tons of oil out there still."
Garron said the wildfire that burned through her study site stimulated microbes that might help clean the hydrocarbons from the soil in time. On the site, horsetails have now joined sedge tussocks, one of the few plants to survive the oil spill.
The cleansing ability of microscopic creatures also was apparent in a fuel spill in Barrow in the mid-1990s that was treated with nitrogen Braddock and others stirred into the gravelly soil.
"Within a summer, it was clean," Braddock said.
The persistence of the 1976 spill near Poker Creek seems to indicate that black spruce growing above permafrost, one of the widest spread ecosystems in Alaska, is also one of its most fragile.
"The black spruce environment
is probably one of the trickiest to clean up after a spill,"
of Alaska Fairbanks, in cooperation with the UAF research community.
Ned Rozell [firstname.lastname@example.org] is a science writer at the institute.
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