Calibration of PurpleAir PA-I and PA-II Monitors Using Daily Mean PM2.5 Concentrations Measured in California, Washington, and Oregon from 2017 to 2021
Abstract
:1. Introduction
2. Materials and Methods
2.1. Obtaining the Data
2.2. Federal and State Agency Data
2.3. Recalibration of PA-II Monitors with PMS-5003 Sensors
- Identify all PurpleAir sites within a specified distance of the target site (e.g., an FRM site). We use several possible distances (0.5, 1, 2, 10 km) to see how distance affects correlations.
- Download the hourly average PM2.5 data calculated using the published calibration factor of 3 in the ALT-CF3 or “PM2.5 alt” algorithms
- Regress the PM2.5 daily measurements at these sites on the target (regulatory) site PM2.5 measurements
- Find the best-fitting (revised) calibration factor by minimizing the mean absolute error (MAE) or the root mean squared error (RMSE) for all pairs of sites. We include both measures to estimate their different effects on the estimated CF.
2.4. New Calibration of PA-I Monitor with PMS-1003 Sensor
3. Results
3.1. Recalibration of PA-II Monitors by Comparison with Regulatory Monitors
3.2. New Calibration of the Outdoor PA-I Monitor with PMS 1003 Sensor vs. Outdoor PA-II Monitors
4. Discussion
4.1. Comparison with Other Algorithms and Effect on the AQI
4.2. Limitations
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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N | Mean | Std. Err. | Min | Z = −1 * | Median | Z = 1 * | Max | |
---|---|---|---|---|---|---|---|---|
PM2.5 | 39,474 | 11.5 | 0.076 | 0.042 | 3.9 | 8.5 | 17 | 577 |
PM2.5 CF3.4 | 39,474 | 11.0 | 0.090 | 0.164 | 2.6 | 6.2 | 18 | 464 |
PM2.5 CF3 | 39,474 | 9.9 | 0.080 | 0.146 | 2.3 | 5.5 | 16 | 414 |
Statistic (N = 117 Sites) | Mean | Std. Err. | Lower Quartile | Median | Upper Quartile | 90th Percentile | Max |
---|---|---|---|---|---|---|---|
slope (centered) | 0.93 | 0.0094 | 0.90 | 0.98 | 0.99 | 0.99 | 0.999 |
Adjusted R² | 0.87 | 0.016 | 0.81 | 0.96 | 0.98 | 0.99 | 0.998 |
Std. Err. of Estimate | 1.7 | 0.10 | 0.81 | 1.5 | 2.3 | 2.8 | 7.4 |
Number of days | 197 | 10.4 | 92 | 178 | 303 | 344 | 497 |
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Wallace, L.; Zhao, T.; Klepeis, N.E. Calibration of PurpleAir PA-I and PA-II Monitors Using Daily Mean PM2.5 Concentrations Measured in California, Washington, and Oregon from 2017 to 2021. Sensors 2022, 22, 4741. https://doi.org/10.3390/s22134741
Wallace L, Zhao T, Klepeis NE. Calibration of PurpleAir PA-I and PA-II Monitors Using Daily Mean PM2.5 Concentrations Measured in California, Washington, and Oregon from 2017 to 2021. Sensors. 2022; 22(13):4741. https://doi.org/10.3390/s22134741
Chicago/Turabian StyleWallace, Lance, Tongke Zhao, and Neil E. Klepeis. 2022. "Calibration of PurpleAir PA-I and PA-II Monitors Using Daily Mean PM2.5 Concentrations Measured in California, Washington, and Oregon from 2017 to 2021" Sensors 22, no. 13: 4741. https://doi.org/10.3390/s22134741
APA StyleWallace, L., Zhao, T., & Klepeis, N. E. (2022). Calibration of PurpleAir PA-I and PA-II Monitors Using Daily Mean PM2.5 Concentrations Measured in California, Washington, and Oregon from 2017 to 2021. Sensors, 22(13), 4741. https://doi.org/10.3390/s22134741