Table 1.
Summarized Hourly Pollutant Concentrations and Calibration Model Performance during the Training and Evaluation Periodsa
| Training Period Statistics | Evaluation Period Statistics | |||||||
|---|---|---|---|---|---|---|---|---|
| Average ± Standard Deviation | Median (5th-95th) | RMSE | r | Average ± Standard Deviation | Median (5th-95th) | RMSE (% bias) | r | |
| PM2.5 (μg/m3) | ||||||||
| Reference | 8.0 ± 6.0 | 7.0 (1.0–18.0) | 8.8 ± 6.0 | 7.0 (1.0–19.0) | ||||
| Uncalibrated Sensor | 12.7 ± 12.3 | 8.8 (1.0–37.5) | 9.2 | 0.84 | 12.4 ± 11.7 | 9.2 (1.0–37.4) | 8.6 (43%) | 0.80 |
| Calibrated Sensor | 8.0 ± 5.4 | 6.6 (2.4–17.9) | 2.8 | 0.89 | 8.0 ± 5.0 | 6.9 (2.5–18.3) | 3.4 (−10%) | 0.85 |
| CO (ppb) | ||||||||
| Reference | 234 ± 144 | 197 (137–446) | 282 ± 248 | 203 (134–688) | ||||
| Uncalibrated Sensor | 0.51 | 0.84 | ||||||
| Calibrated Sensor | 234 ± 128 | 199 (151–417) | 60.5 | 0.90 | 297 ± 238 | 218 (164–688) | 58.9 (5.6%) | 0.97 |
| NO2 (ppb) | ||||||||
| Reference | 7.9 ± 7.9 | 5.0 (1.0–26.0) | 8.1 ± 7.0 | 5.0 (1.0–23.0) | ||||
| Uncalibrated Sensor | 0.71 | 0.68 | ||||||
| Calibrated Sensor using Reference Data for Pollutant Predictors | 8.1 ± 7.3 | 5.9 (2.1–23.7) | 3.3 | 0.91 | 7.8 ± 5.7 | 5.9 (1.8–19.1) | 3.5 (−9.0%) | 0.88 |
| Calibrated Sensor using Sensor Data for Pollutant Predictors | 7.9 ± 7.1 | 5.9 (0.5–23.5) | 3.6 | 0.90 | 9.4 ± 5.8 | 7.6 (0.5–20.4) | 3.6 (12%) | 0.88 |
| O3 (ppb) | ||||||||
| Reference | 35.5 ± 15.7 | 36.0 (7.0–60.0) | 28.5 ± 14.9 | 28.0 (4.0–56.0) | ||||
| Uncalibrated Sensor | 0.52 | 0.52 | ||||||
| Calibrated Sensor using Reference Data for Pollutant Predictors | 35.8 ± 13.7 | 36.5 (10.5–58.1) | 6.9 | 0.90 | 28.4 ± 13.6 | 29.8 (7.0–55.8) | 7.4 (−7.1%) | 0.86 |
| Calibrated Sensor using Sensor Data for Pollutant Predictors | 35.6 ± 13.6 | 36.1 (9.4–57.6) 7.1 | 0.90 | 28.3 ± 15.5 | 26.6 (3.6–55.5) | 7.0 (−4.0%) | 0.89 | |
| NO (ppb) | ||||||||
| Reference | 3.0 ± 11.0 | 0.5 (0.1–11.2) | 3.3 ± 10.0 | 0.6 (0.1–16.5) | ||||
| Uncalibrated Sensor | 0.81 | 0.77 | ||||||
| Calibrated Sensor using Reference Data for Pollutant Predictors | 3.0 ± 10.3 | 0.6 (0.01–12.3) | 3.0 | 0.96 | 2.8 ± 8.3 | 0.5 (0.01–13.7) | 3.3 (−15%) | 0.96 |
| Calibrated Sensor using Sensor Data for Pollutant Predictors | 3.0 ± 10.0 | 0.6 (0.01–12.9) | 3.4 | 0.95 | 3.3 ± 7.8 | 0.8 (0.01–13.9) | 3.2 (−2.7%) | 0.97 |
| Temperature (°C) | ||||||||
| Ambient Reference | 15.1 ± 9.7 | 16.6 (−0.5 to 29.4) | 13.0 ± 10.2 | 11.6 (−1.6 to 28.8) | ||||
| Internal Sensor | 20.8 ± 10.9 | 21.8 (3.4–38.4) | 19.2 ± 10.6 | 18.0 (3.1–37.4) | ||||
| RH (%) | ||||||||
| Ambient Reference | 61.8 ± 19.9 | 61 (29–91) | 65.4 ± 17.6 | 66 (38–91) | ||||
| Internal Sensor | 49.8 ± 16.0 | 49.4 (24.2–73.6) | 52.4 ± 13.8 | 53.4 (30.4–73.0) | ||||
a
In the case of NO2, O3, and NO, only periods when the predictors for both models were available were included in the summary values, which allows for direct comparison.