https://doi.org/10.5061/dryad.pc866t1x6

This dataset was collected by Colorado State University (CSU) students during the spring 2023 and fall 2023 semesters as part of a course in the Department of Atmospheric Science (ATS-716: Air Quality Characterization). Measurements of volatile organic compounds (VOCs) were collected in Northern Colorado, using a low-cost sensor called SENSIT SPOD. The SENSIT SPOD sensor package combines wind field and air pollutant concentration measurements to detect emission plumes and locate the source of those emissions. The sensor measures non-speciated, uncalibrated concentrations of a subset of VOCs. The sensor also measures temperature, relative humidity, pressure, and wind direction and speed. The SPODs were used to trigger the collection of whole air samples during periods with higher concentrations of VOCs. Air samples from the triggered canisters were analyzed at CSU using Gas Chromatography (GC) to provide a measure of approximately 50 VOCs. An integrated canister was used to measure the average concentration of approximately 50 VOCs over a one-week period. After collection, sample air in the canisters was analyzed at CSU using Gas Chromatography (GC).

Description of the data and file structure

This dataset contains information on VOC concentration and meteorological conditions collected in the Bella Romero neighborhood (40.405, -104.659) in Greeley, CO. Measurements were taken over two periods: February 6, 2023 to May 2, 2023 (spring semester) and September 7, 2023 to December 19, 2023 (fall semester). There were no triggered canister measurements for spring 2023. The dataset includes 3 different files: 1) SPOD_PID_Data.zip; 2) Triggered_Canisters.csv; and 3) Integrated_Canisters.csv. The following provides a description of each of these files:

●  SPOD_PID_Data.zip

○  Zipped folder containing daily comma-delimited CSV files. The file contains 21 columns of data, and 7 empty columns that are automatically generated, but were not measured by the SPODs deployed in this instance.

○  File naming convention: SPOD_DATA_EXPORT_IDNUMBER_MMDDYY.csv

○  IDNUMBER: 1264

●  Triggered_Canisters_2023_all.csv

**  ○           VOC concentration and meteorological data associated with SPOD triggered events. PID trigger thresholds were as follows:**

• Initial (September 7 - September 26): 250 (static), 130 ppb (differential)
• Updated (September 26 - October 19): 200 ppb (static), 130 ppb (differential)
• Additionally updated (October 19 - October 31): 150 ppb (static), 75 ppb (differential)
• Final update (October 31 - December 8): 130 ppb (static), 60 ppb (differential)
• NaN indicates the data is not available for a specific compound for a specific canister

**  ○  Duration of sample: 2 min **

○  Data are contained in a comma-delimited CSV file with 59 columns.

●  Integrated_Canisters_2023_all.csv

○  The average concentration of VOCs in whole air samples collected over approximately one-week time periods at each site.

○  Data are contained in a comma-delimited CSV file with 54 columns.

Variable information:

File Name: SPOD_PID_Data.zip

 

 File Name: Triggered_Canisters_2023_all.csv

 

File Name: Integrated_Canisters_2023_all.csv

 

 

Environmental or experimental conditions:

The instrumentation was located over largely bare ground near livestock. Instruments were placed inside of a cage to prevent interference from livestock. The broader region around Bella Romero has extensive oil and gas development, agricultural facilities, and industrial facilities. The site was also located near a road frequently used to access a local school during morning dropoff and afternoon pickup times.

Uncertainty, precision, and accuracy of measurements:

The GC analysis precision, accuracy and combined uncertainty of individual VOCs range from 1 - 13%. The measurement uncertainty for the methane is 2%. The uncertainty associated with the flow controller used to fill the integrated canisters is +/- 13%.

Standards, calibrations, and quality controls:

All whole air samples have been analyzed as described in Benedict et al. (2019) and Hecobian et al., (2019).

 Benedict, K. B., Zhou, Y., Sive, B. C., Prenni, A. J., Gebhart, K. A., Fischer, E. V., Evanoski-

Cole, A., Sullivan, A. P., Callahan, S., Schichtel, B. A., Mao, H., Zhou, Y., and Collett Jr., J. L.: Volatile organic compounds and ozone in Rocky Mountain National Park during FRAPPÉ, Atmos. Chem. Phys., 2019, 19, 499–521, https://doi.org/10.5194/acp-19-499-2019.

Hecobian, A.; Clements, A. L.; Shonkwiler, K. B.; Zhou, Y.; MacDonald, L. P.; Hilliard, N.; Wells,

B. L.; Bibeau, B.; Ham, J. M.; Pierce, J. R.; Collett, J. L. Air Toxics and Other Volatile Organic Compound Emissions from Unconventional Oil and Gas Development. Environ. Sci. Technol. Lett. *2019, *6, 720– 726, DOI: 10.1021/acs.estlett.9b00591

Additional Information:

Plume extrapolation of the triggered events:

In each triggered event, an approximately two-minute whole air sample was collected and analyzed. A preliminary extrapolation of the two-minute VOC sample into a one-hour concentration was performed but is not reported here. The performance of plume extrapolation varied due to the number of samples collected during each plume and the different assumptions made during calculations (i.e., the extrapolation methodology used). Contact the PI for more information about plume extrapolation.

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