Alaska scientist uses isotopes
to trace marijuana
By Ned Rozell
May 09, 2007
Police officers don't often get a straight story when they ask
a driver where he got that bag of marijuana under his car seat.
In the near future, they might be able to ask the marijuana itself.
Using a process called stable-isotope analysis, Alaska scientists
have been working with law enforcement officials to trace marijuana
to the area in which it grew.
Marijuana grown in
the Goldstream Valley north of Fairbanks. Police
officers found more than 400 plants at the scene a few years
Photo courtesy UAF Police Department Investigator Steve Goetz.
Matthew Wooller is one of those scientists. He runs the Alaska
Stable Isotope Facility at the University of Alaska Fairbanks,
where researchers break substances down to their chemical elements
to learn where they came from. Wooller went to a conference in
New Zealand a few years ago where a scientist lectured about
using stable isotopes to track people and counterfeit money,
to sniff out the source of explosions, and to find the sources
of illegal drugs. The talk inspired him.
"When I was flying back to Alaska, I thought, 'I'd love
to do an Alaska forensic drug study,'" he said.
Marijuana is the most abused and widespread drug in Alaska, according
to the U.S. Drug Enforcement Administration. Alaska features
potent strains from the Matanuska Valley that make the state
an exporter as well as an importer. Law enforcers would like
to know the proportions of both, so they know where to focus
After Wooller applied for a permit from the D.E.A. to work with
marijuana in his lab, he needed to find a varied supply of the
drug. He went to the UAF Police Department and asked for help.
After convincing a few officers that no, he was really a scientist,
he got to speak with Investigator Steve Goetz and Lieutenant
Syrilyn Tong, who agreed to help him out.
The UAF Police Department, with help from federal, state, and
local law enforcement agencies in Alaska, was able to provide
Wooller's team with marijuana samples from different areas in
Alaska. They also gave Wooller and his research team of Norma
Haubenstock and Tim Howe samples that officers had confiscated
on and around the Fairbanks campus.
Wooller and his group then went to work, taking pinhead-size
bits of marijuana and vaporizing them, then running the gas samples
through a stable isotope ratio mass spectrometer. That device
allows them to measure the composition of chemical elements-such
as oxygen, hydrogen, carbon, and nitrogen-in each sample. Stable
isotopes are atoms of the same element that have slight differences
in their atomic masses, and that's what enables scientists to
track things down with them.
For example, the stable oxygen isotope signature of well water
in Anchorage is lower than that of tap water in Albany, New York.
Leaves, buds, and stems of marijuana retain an isotopic signature
of the water supplied to them when they were growing, and that
allows researchers to tease out the latitude at which the marijuana
"Marijuana grown in Alaska using Alaska water should have
a distinct chemical composition, completely different than marijuana
grown in Mexico," Wooller said. "And even Juneau and
Fairbanks have very different tap-water signatures."
In his studies, Wooller found marijuana with both high and low
isotopic values, which suggests that some was imported from outside
Alaska and some was grown in the state.
"The interesting thing we found is that there's a lot of
marijuana being imported," said Goetz, the UAF investigator.
"We had thought that a lot higher percentage of marijuana
in our area was locally grown."
Wooller, who studies the isotopic signatures of fossil plants
and animals most of the time, is looking for more funding to
continue the marijuana study, which is on hold at the moment.
Goetz hopes new money comes through, because law enforcers would
like another tool to help trace marijuana to its source.
"We're still collecting samples for him," Goetz said.
"I'm hoping he continues with his project and gets more
definitive answers for us."
This column is provided
as a public service by the Geophysical
Institute, University of
Alaska Fairbanks, in cooperation with the UAF research community.
Ned Rozell [ email@example.com
] is a science writer at the institute.
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