Dataset associated with "Laboratory Evaluation of Low-cost PurpleAir PM Monitors and In-field Correction using Co-located Portable Filter Samplers"

Jessica Tryner (1), Christian L'Orange (1), John Mehaffy (1), Daniel Miller-Lionberg (2), Josephine C. Hofstetter (2), Ander Wilson (3), John Volckens (1)*
 
1. Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, Colorado 80523
2. Access Sensor Technologies, 2401 Research Blvd, Suite 107, Fort Collins, Colorado 80526
3. Department of Statistics, Colorado State University, 1801 Campus Delivery, Fort Collins, Colorado 80523

*Please contact John Volckens (john.volckens@colostate.edu) regarding this dataset.

See the manuscript for details on data collection, quality control, and analysis:
Tryner, J., L’Orange, C.L., Mehaffy, J., Miller-Lionberg, D., Hofstetter, J.C., Wilson, A., Volckens, J., 2019. Laboratory evaluation of low-cost PurpleAir PM monitors and in-field correction using co-located portable filter samplers. Atmospheric Environment 220, 117067. https://doi.org/10.1016/j.atmosenv.2019.117067

The first file in this dataset, "lab_evaluation_summary.csv", includes concentrations of NIST Urban Particulate Matter measured over ~40-minute periods using PurpleAir monitors and a tapered-element oscillating microbalance (TEOM). All concentrations are in units of micrograms per cubic meter. These data were collected in a laboratory aerosol chamber at Colorado State University on 2018-08-20 and 2018-12-17. 

The "lab_evaluation_summary.csv" data file includes the following columns:

1.  evaluation - denotes whether the data point was collected during the pre- or post-deployment laboratory evaluation,
2.  point - an identifier for the unique ~40-minute long steady-state concentration point,
3.  duration - the duration of the steady-state concentration point (minutes),
4.  teom - the time-averaged concentration measured by the TEOM over the duration of the steady-state concentration point (micrograms per cubic meter)
5.  pa_id - the identifier for the PurpleAir monitor,
6.  size_fraction - specifies the size fraction associated with the PM concentration given in the "purple_air" column (PM2.5), 
7.  correction - specifies whether the PM concentration given in the "purple_air" column was labeled "CF=1" or "ATM" in the log file recorded using PurpleAir firmware version 2.50i,
8.  purple_air - the time-averaged PM concentration reported by the PurpleAir monitor over the duration of the steady-state concentration point (micrograms per cubic meter), 
9.  pa_temp - the time-averaged temperature reported by the PurpleAir monitor over the duration of the steady-state concentration point (Celsius),
10. pa_rh - the time-averaged relative humidity reported by the PurpleAir monitor over the duration of the steady-state concentration point (%).

The second file in this dataset, "field_deployment_summary.csv", includes ambient PM2.5 concentrations measured over 72- or 48-hour periods using portable filter samplers (UPAS installed in ASPEN boxes), PurpleAir monitors, and conventional 16.7 L/min filter samplers. These data were collected outdoors in Fort Collins, Colorado, USA between 2018-10-22 and 2018-12-06. 

Each row in the "field_deployment_summary.csv" data file represents a unique filter sample-PurpleAir pair. The data file includes the following columns:

1.  site - the site ID (corresponding to Figure 1 in the associated manuscript),
2.  latitude - the latitude of the site (degrees),
3.  longitude - the longitude of the site (degrees),
4.  sample_type - denotes the type of filter sample (either "UPAS" or "reference"), 
5.  pa_id - the ID of the PurpleAir monitor co-located with the filter sample,
6.  aspen_id - the ID of the ASPEN box used to collect the filter sample (for UPAS filter samples) or co-located with the filter sample (for reference filter samples),
7.  start_time - the start time of the filter sample (UTC),
8.  end_time - the end time of the filter sample (UTC),
9.  duration - the duration of the filter sample (hours),
10. target_duration - the duration for which the filter sample was intended to run (hours),
11. temperature - the time-averaged temperature measured at the Colorado State University main campus weather station over the duration of the sample (Celsius),
12. rh - the time-averaged relative humidity measured at the Colorado State University main campus weather station over the duration of the sample (%),
13. temp_pa - the time-averaged temperature reported by the PurpleAir monitor over the duration of the sample (Celsius),
14. rh_pa - the time-averaged relative humidity reported by the PurpleAir monitor over the duration of the sample (%),
15. filter_mass - the mass of PM2.5 accumulated on the filter sample (micrograms),
16. volume - the volume of air sampled through the filter (liters),
17. pm25 - the PM2.5 concentration derived from the filter sample (micrograms per cubic meter),
18. flow_pre - the volumetric flow rate through the 16.7 L/min "reference" filter sample at the start of the sample period (liters per minute),
19. flow_post - the volumetric flow rate through the 16.7 L/min "reference" filter sample at the end of the sample period (liters per minute),
20. pa_data_frac - the fraction of the duration of the filter sample for which PurpleAir data were successfully logged and passed the quality assurance check,
21. pa_pm25_cf1_a - the time-averaged (over the duration of the filter sample) PM2.5 concentration measured by Plantower sensor "A" and labeled "CF=1" in the PurpleAir log file (micrograms per cubic meter),
22. pa_pm25_cf1_b - the time-averaged (over the duration of the filter sample) PM2.5 concentration measured by Plantower sensor "B" and labeled "CF=1" in the PurpleAir log file (micrograms per cubic meter),
23. pa_pm25_atm_a - the time-averaged (over the duration of the filter sample) PM2.5 concentration measured by Plantower sensor "A" and labeled "ATM" in the PurpleAir log file (micrograms per cubic meter),
24. pa_pm25_atm_b - the time-averaged (over the duration of the filter sample) PM2.5 concentration measured by Plantower sensor "B" and labeled "ATM" in the PurpleAir log file (micrograms per cubic meter),
25. pa_pm25_atm - the average of "pa_pm25_atm_a" and "pa_pm25_atm_b" (micrograms per cubic meter),
26. cf_lab - the gravimetric correction factor for the PurpleAir monitor derived from the pre-deployment laboratory evaluation, 
27. cf_rh - the value obtained by dividing the time-averaged (over the duration of the filter sample) relative humidity-corrected PurpleAir PM2.5 "ATM" concentration by "pa_pm25_atm", 
28. cf_monthly - the gravimetric correction factor for the PurpleAir monitor derived from monthly colocation with a UPAS filter sample, 
29. cf_weekly - the gravimetric correction factor for the PurpleAir monitor derived from weekly colocation with a UPAS filter sample, 
30. cf_concurrent - the gravimetric correction factor for the PurpleAir monitor derived from concurrent colocation with a UPAS filter sample

This dataset also includes three .zip files:

PurpleAir.zip - Raw data recorded by the PurpleAir monitors during the two laboratory evaluations, the break-in period, and the field network deployment (1943 .csv files and a README.txt file)

ASPEN.zip - Raw data recorded by the ASPEN boxes during the field deployment (242 .txt files, a README.txt file, and a README.pdf file)

TEOM.zip - Raw data recorded by a tapered element oscillating microbalance (TEOM) during the two laboratory evaluations (2 .csv files and a README.txt file)

Recommended citation:
Tryner, J., L’Orange, C.L., Mehaffy, J., Miller-Lionberg, D., Hofstetter, J.C., Wilson, A., & Volckens, J. (2019). Dataset associated with "Laboratory Evaluation of Low-cost PurpleAir PM Monitors and In-field Correction using Co-located Portable Filter Samplers." Colorado State University. Libraries. http://dx.doi.org/10.25675/10217/195445