Geographical origin determination of cannabis
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Geographical origin determination of cannabis is the measurement of cannabis material to work out where it was grown. The measurements in published use are the ratios of stable isotopes in the plant tissue, the infrared spectrum of the dried material and the concentrations of mineral elements it took up. None of them reads a place off a sample on its own: each is compared with measurements of material of known origin, and what the comparison can settle is set by how much such reference material exists and where it came from.[1]
The ratios record the conditions in which the sampled tissue grew, among them the water the plant had, whether it grew under a roof and the fertiliser it was given, and, for strontium, the rock beneath the field.[2][3] What they follow is the growing of that tissue and not the plant's ancestry, so they cannot confirm which landrace a sample belongs to, and material reproduced in another place carries the signature of the place it was grown out in.
The published work was done mostly for drug-enforcement casework, on material taken by police: plants from eradicated gardens recorded by county, consignments stopped at borders and retail seizures. The regions a model separates are therefore the regions its samples came from.[4][5]
Carbon and nitrogen
Cannabis grown in Australia, Papua New Guinea and Thailand covered nearly the whole range of carbon isotope values reported for C3 plants, from −36 to −25 parts per thousand, and the values did not separate the three countries. Within one growing site they did separate conditions: well-watered plants on a plantation averaged −30.0 parts per thousand against −26.4 for plants given little irrigation, and plants grown indoors averaged −31.8 against −27.9 for plants grown outdoors. Nitrogen values followed the fertiliser, from −0.2 to 2.2 parts per thousand for mineral fertilisers and from 7.6 to 22.7 for those based on manure, and the plant values tracked the soil and fertiliser values at a site.[2]
A survey of 508 samples from known counties of the United States, with a further 31 from one location and samples from Mexico and Colombia, found inflorescences slightly higher than leaves in both carbon and nitrogen. Samples that the carbon values placed outdoors were usually recorded as outdoor-grown by the agency that supplied them, while the samples recorded as indoor-grown had the most negative carbon values, although many of those also fell in the range of outdoor material.[4]
Carbon values well below the plant range point to the air the plant was given rather than the climate. Of samples held in Alaska, twelve ran from −36.1 to −61.8 parts per thousand, which was put down to carbon dioxide released from cylinders or fermenters in enclosed growing rooms.[6]
Measuring single compounds instead of the whole tissue did not sharpen the comparison. Bulk carbon values told five samples apart where values measured on the extracted cannabinoids did not separate one pair, and the cannabinoids were lighter than the bulk tissue, by 1.6 parts per thousand for THC, 1.7 for cannabinol and 2.2 for cannabidiol.[7]
Hydrogen, oxygen and strontium
Hydrogen and oxygen in plant tissue follow the water the plant used, which varies with latitude, altitude and distance from the sea. In Alaskan material the oxygen values ran from 10.4 to 37.0 parts per thousand and the hydrogen values from −203.1 to −136.7 for samples from known sites in the state, and the wider ranges measured on samples of unknown origin were read as a sign that those samples came from many latitudes.[6]
Models built on hydrogen and carbon values from eradication and border specimens were tested against 60 further eradication specimens whose origins were withheld. The two models for region of origin were right for 60 to 67 per cent of them, and the model for growing environment for 86 per cent.[5] The same approach applied to 628 retail seizures from more than 50 municipalities grouped into 22 retail areas and gave each area a mixture of sources, domestic and foreign.[8]
Strontium is taken up from the ground and its isotope ratio follows the rock. Cannabis grown in 79 counties of the United States gave ratios that correlated with the ratio modelled for the bedrock beneath each county, with more values above the modelled line than below it, which the authors attributed in part to carbonate rocks.[3]
Infrared spectra
An infrared spectrum of dried material records its chemical make-up, cell-wall material and cannabinoids together, and is read by comparing it with spectra of material of known origin through a statistical model. Spectra of 47 samples from Brazil and 18 from Colorado, taken by attenuated total reflectance and sorted by linear discriminant analysis, assigned up to 95 per cent of the Brazilian samples and all of the Colorado samples to the right place.[9]
A study of 200 flower tops from four regions of North India recorded 1,000 spectra, reduced them by principal component analysis and trained four models on them, of which an artificial neural network classified the samples best. The component that contributed most to the sorting was associated with cell-wall polysaccharides, lignin, pectin, tetrahydrocannabinolic acid and THC. Its authors describe the work as a proof of concept.[10]
A model of this kind sorts a sample among the places whose material trained it, and has nothing to say about a place that was not in the training set.[10][9]
Mineral elements
Patterns of association between the elements in a plant, measured on single spots by laser ablation, were applied to sourcing cannabis crops as early as 1998.[11] Twelve elements measured in cannabis seized in Ghana, together with soils from cannabis farms there, separated the farms from one another and associated the seized samples with two regions of the country.[12]
Strontium ratios measured on the stalks and fibre of hemp grown in Italy ran from 0.7085 to 0.7105 and reflected the geology of the growing regions, and the elemental profiles clustered the northern samples apart from the southern ones, although not completely.[13]
Seed, fibre and extracts
Work on the crop grown for food and fibre has measured parts of the plant separately. In hemp from eight regions of Italy the hydrogen, carbon, oxygen and sulphur values of roots, stems, inflorescences and seeds, and of five seed oils, varied with latitude and with the climate the plants grew in, while the nitrogen values separated crops grown under conventional fertilisation from those grown under organic fertilisation.[14]
Strontium ratios were measured on a hemp fabric from Iceland thought to have been made in the early 17th century, against a soil sample and fibre from hemp recently grown on the island, which has one young volcanic soil type. The fibres of the fabric did not match the island, and the authors suggest France or Scotland as the source.[15]
Isotope measurements have also been used on extracts to tell a plant source from a laboratory one. Hydrogen and oxygen values separated cannabidiol extracted from the plant from cannabidiol made by chemical synthesis, with thresholds for plant-derived material of −215 parts per thousand for hydrogen and 23.4 for oxygen at a confidence level of 95 per cent.[16] Carbon values and the ratio of mirror-image forms of single terpenes, measured together on essential oils, fell outside the ranges of oils of known provenance for some of 19 oils bought in shops.[17]
What a measurement settles
A measurement of a sample is a number until it is set against numbers from material whose origin is known. Where that reference material exists for the places in question, the comparison can support or fail to support the claim that the sample grew in one of them; where it does not exist, the measurement supports nothing about place.[1][3]
What the signal records is the growing of that tissue. Carbon and nitrogen describe the conditions, so they can distinguish a shaded indoor crop from a field crop and one fertiliser regime from another, and two crops grown in the same field would read alike whatever their ancestry.[2][4] Strontium follows the rock, which ties a sample to a geology rather than to a grower.[3] An infrared model places a sample among the regions it was trained on.[10] The authors of the nitrogen work propose their measurement for matching a seized sample to a particular crop, a comparison between two samples rather than an assignment to a region.[2]
See also
References
- ↑ 1.0 1.1 Cerling, T.E.; Barnette, J.E.; Bowen, G.J.; Chesson, L.A.; Ehleringer, J.R.; et al. (2016). "Forensic stable isotope biogeochemistry". Annual Review of Earth and Planetary Sciences. 44 (1): 175–206. doi:10.1146/annurev-earth-060115-012303.
- ↑ 2.0 2.1 2.2 2.3 Denton, T.M.; Schmidt, S.; Critchley, C.; Stewart, G.R. (2001). "Natural abundance of stable carbon and nitrogen isotopes in Cannabis sativa reflects growth conditions". Australian Journal of Plant Physiology. 28 (10): 1005–1012. doi:10.1071/PP01066.
- ↑ 3.0 3.1 3.2 3.3 West, Jason B.; Hurley, Janet M.; Dudás, Francis Ö.; Ehleringer, James R. (2009). "The stable isotope ratios of marijuana. II. Strontium isotopes relate to geographic origin". Journal of Forensic Sciences. 54 (6): 1261–1269. doi:10.1111/j.1556-4029.2009.01171.x.
- ↑ 4.0 4.1 4.2 West, Jason B.; Hurley, Janet M.; Ehleringer, James R. (2009). "Stable isotope ratios of marijuana. I. Carbon and nitrogen stable isotopes describe growth conditions". Journal of Forensic Sciences. 54 (1): 84–89. doi:10.1111/j.1556-4029.2008.00909.x.
- ↑ 5.0 5.1 Hurley, J.M.; West, J.B.; Ehleringer, J.R. (2010). "Stable isotope models to predict geographic origin and cultivation conditions of marijuana". Science & Justice. 50 (2): 86–93. doi:10.1016/j.scijus.2009.11.003.
- ↑ 6.0 6.1 Booth, A.L.; Wooller, M.J.; Howe, T.; Haubenstock, N. (2010). "Tracing geographic and temporal trafficking patterns for marijuana in Alaska using stable isotopes (C, N, O and H)". Forensic Science International. 202 (1–3): 45–53. doi:10.1016/j.forsciint.2010.04.025.
- ↑ Muccio, Z.; Wöckel, C.; An, Y.; Jackson, G.P. (2012). "Comparison of bulk and compound-specific δ13C isotope ratio analyses for the discrimination between cannabis samples". Journal of Forensic Sciences. 57 (3): 757–764. doi:10.1111/j.1556-4029.2011.02046.x.
- ↑ Hurley, J.M.; West, J.B.; Ehleringer, J.R. (2010). "Tracing retail cannabis in the United States: geographic origin and cultivation patterns". International Journal of Drug Policy. 21 (3): 222–228. doi:10.1016/j.drugpo.2009.08.001.
- ↑ 9.0 9.1 Ramos, M.F.; Kinney, C.A.; Coblinski, J.A.; Fett, M.S.; Dick, D.P.; de Oliveira Camargo, F.A. (2024). "ATR-FTIR spectroscopy and LDA: a rapid, non-destructive and cost effective strategy to trace the geographical origin of Cannabis sativa L." Forensic Sciences Research. 10 (2) owae016. doi:10.1093/fsr/owae016.
- ↑ 10.0 10.1 10.2 Singh, M.; Sharma, A.; Sharma, V. (2026). "Tracing the roots of illicit Cannabis: a machine learning-assisted ATR-FTIR proof-of-concept study for geographical origin classification". Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 366 128847. doi:10.1016/j.saa.2026.128847.
- ↑ Watling, R.J. (1998). "Sourcing the provenance of cannabis crops using inter-element association patterns 'fingerprinting' and laser ablation inductively coupled plasma mass spectrometry". Journal of Analytical Atomic Spectrometry. 13 (9): 917–926. doi:10.1039/a800338f.
- ↑ Douvris, Chris; Bentil, Edward; Ayensu, Isaac; Osei Akoto, Clement; Amponsah, Isaac Kingsley; Adu, Joseph; Bussan, Derek (2022). "Trace metals in cannabis seized by law enforcement in Ghana and multivariate analysis to distinguish among different cannabis farms". Toxics. 10 (10) 567. doi:10.3390/toxics10100567.
- ↑ Rivi, M.; D'Eusanio, V.; Marchetti, A.; Bonfiglioli, E.; Tassi, L. (2025). "Elemental composition and strontium isotopic ratio analysis of industrial hemp (Cannabis sativa L.) for textile applications". Molecules. 30 (23) 4573. doi:10.3390/molecules30234573.
- ↑ Calvi, M.; Bontempo, L.; Pizzini, S.; Cucinotta, L.; Camin, F.; Stenni, B. (2022). "Isotopic characterization of Italian industrial hemp (Cannabis sativa L.) intended for food use: a first exploratory study". Separations. 9 (6) 136. doi:10.3390/separations9060136.
- ↑ Skoglund, G.; Monti, C. (2025). "First strontium isotope analysis of a heritage hemp fabric in Iceland". Fornvännen. 2025 (4): 275–285. doi:10.62077/qvoo62.lrqrnm.
- ↑ Perini, M.; Gaggiotti, A.; Pianezze, S.; Ziller, L.; Larcher, R. (2023). "Stable isotope ratio analysis for authentication of natural antioxidant cannabidiol (CBD) from Cannabis sativa". Antioxidants. 12 (7) 1421. doi:10.3390/antiox12071421.
- ↑ Cucinotta, L.; De Grazia, G.; Micalizzi, G.; Bontempo, L.; Camin, F.; et al. (2022). "Simultaneous evaluation of the enantiomeric and carbon isotopic ratios of Cannabis sativa L. essential oils by multidimensional gas chromatography". Analytical and Bioanalytical Chemistry. 414 (18): 5643–5656. doi:10.1007/s00216-022-04035-1.