Sierra Brown

Project title: Analysis of Spatial and Temporal Variation Among Terpenes Derived from Cannabis and Forest Environments

Degree: MS (Thesis) | Program: Occupational Hygiene (OH) | Project type: Thesis/Dissertation
Completed in: 2022 | Faculty advisor: Christopher D. Simpson


Background: Terpenes are a broad class of volatile and semi volatile organic compounds with over 40,000 different known structures, that are emitted by a wide variety of flora. Terpene concentrations vary in different forest settings. This can be due to different combinations of many factors that can cause fluctuations and changes in terpene emissions including the specific plant species present, chemical reactivity, emission rates, as well as weather conditions such as wind speed, wind direction, temperature, relative humidity, pressure, and rainfall. In the current project spatial and temporal variability in terpene concentrations will be examined in forest, urban, and cannabis manufacturing facilities using novel thermal desorption tubes that have been designed specifically for analysis of terpenes.

Methods: This study was broken up into two phases. The first phase selected the parameters for terpene sampling by selecting the Carbotrap glass T420 thermal desorption tubes specifically for sampling terpenes as well as the sample duration, flow rates and sample volume for each sample. The sample period was set to 120 minutes at a flow rate of 200mL/min was chosen to allow for a sample volume of around 24L. This was chosen for the outdoor forest and urban park samples. During Phase two, samples were taken at three urban park/forest environments and outside of two indoor grown cannabis facilities. Samples were taken with the sample parameters from phase one and two sample periods were carried out at each location.

Results: Indoor cannabis terpene profiles were observed to be different than the outdoor samples: -myrcene was the most abundant terpene in the indoor cannabis facility samples, and terpene concentrations inside the cannabis facility were very high compared to the concentrations found in the outdoor forest and park locations. -Pinene was the dominant terpene in most of the outdoor samples. Some samples collected were below the limit of detection for -Pinene, but mostly the tubes were able to detect the most abundant terpenes present. Overall, the terpene data exhibit substantial variability at each location, however with the small sample sizes for all the sample locations it is not possible to state definitively whether this variability is driven by specific environmental conditions.

Conclusions: The terpenes in highest abundance for outdoor forest environments were -pinene, followed by -pinene, d-limonene, borneol, 3-carene among others in lower concentrations. The terpenes that were most abundant inside cannabis facilities were -myrcene followed by smaller concentrations of -pinene, -pinene, and limonene. From the results of this study in outdoor forest settings and urban parks, larger sample sizes should be implemented in future studies to account for the high variability of terpene composition and concentrations.