Tracing geographic and temporal trafficking patterns for marijuana in Alaska using stable isotopes (C, N, O and H)

Abstract

A large proportion of Alaska Bureau of Alcohol and Drug Enforcement's time is spent controlling the production and distribution of marijuana. Marijuana in Alaska can originate from within (e.g., Fairbanks and the Matanuska-Susitna Valley) or from outside Alaska (e.g., Latin America, Canada and other locations in the United States of America). However it is difficult to track the supply proportions from various potential geographic areas in remote areas of the globe, such as Alaska. This is due to an insufficient ability to trace the source regions from which confiscated marijuana was originally grown. We analyzed multiple stable isotopes (C, N, O and H) in marijuana confiscated in Alaska, to identify the likely geographic source from which the marijuana originated. Fifty-six of the marijuana samples were from known grow locations in Alaska. These samples exhibited stable oxygen and hydrogen isotope ratios ( δ 18O and δD) of 10.4‰ to 37.0‰ and −203.1‰ to −136.7‰, respectively. Stable carbon and nitrogen isotope ratios ( δ 13C and δ 15N) of the same samples ranged from −53.8‰ to −26.4‰ and −12.5‰ to 12.1‰, respectively. We use these data to compare with stable isotope analyses of marijuana confiscated in Alaska, but from unknown grow locations, which were found to have δ 18O and δD ranging from 10.0‰ to 34.5‰ and −214.6‰ to −107.5‰, respectively. The large range of data suggests that the samples originated from multiple sources ranging from low to high latitudes. A large range in δ 15N values from the samples was also evident (−5.0‰ to 14.7‰). Most intriguing of all was the unexpected large range in the stable carbon isotope compositions of the samples (−61.8‰ to −24.6‰). Twelve of the samples were found to have an exceedingly low δ 13C values (−36.1‰ to −61.8‰) compared to typical δ 13C values of other plants using C3 photosynthesis. Interior growing conditions (e.g., hydroponic and green house) and a variety of CO 2 sources (e.g., CO 2 from tanks and fermentation CO 2 generators) supplied to growing marijuana (in addition to atmospheric CO 2) that are sometimes used to improve marijuana yields likely account for these exceptionally low δ 13C values. Our project has implications for monitoring broad scale trafficking patterns over time in relatively remote regions such as Alaska, where the resources allocated for law enforcement must be utilized over a wide geographic area.