Alaska scientist uses isotopes to trace marijuana

May 9, 2007

By Ned Rozell
Fairbanks, Alaska - 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.

Marijuana grown in the Goldstream Valley north of Fairbanks. Police officers found more than 400 plants at the scene a few years ago. Photo courtesy UAF Police Department Investigator Steve Goetz.

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.

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 their energy.

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 grew.

"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.

"We¹re still collecting samples for him," Goetz said. "I'm hoping he continues with his project and gets more definitive answers for us."