Farooqui, Z.; Biswas, J.; Saha, J. Long-Term Assessment of PurpleAir Low-Cost Sensor for PM2.5 in California, USA. Pollutants2023, 3, 477-493.
Farooqui, Z.; Biswas, J.; Saha, J. Long-Term Assessment of PurpleAir Low-Cost Sensor for PM2.5 in California, USA. Pollutants 2023, 3, 477-493.
Farooqui, Z.; Biswas, J.; Saha, J. Long-Term Assessment of PurpleAir Low-Cost Sensor for PM2.5 in California, USA. Pollutants2023, 3, 477-493.
Farooqui, Z.; Biswas, J.; Saha, J. Long-Term Assessment of PurpleAir Low-Cost Sensor for PM2.5 in California, USA. Pollutants 2023, 3, 477-493.
Abstract
Regulatory monitoring networks are often too sparse to support community-scale PM2.5 exposure assessment while emerging low-cost sensors have the potential to fill in the gaps. Recent advances in air quality monitoring have produced portable, easy-to use, low-cost, sensor-based monitors, which has given a new dimension to the air pollutant monitoring and has democratized the air quality monitoring process by making monitors and results directly available at community level. This study used PurpleAir(c) sensors for PM2.5 assessment in California, USA. Evaluation of PM2.5 from sensors included Quality Assurance & Quality Control (QAQC) procedures, assessment with respect to reference monitored PM2.5 concentrations, and formulation of a decision support system integrating these observations using geostatistical techniques. The hourly and daily average observed PM2.5 concentrations from PurpleAir monitors followed the trends of observed PM2.5 at regulatory monitors. PurpleAir monitored PM2.5 also captured the peak PM2.5 concentrations due to incidents like forest fire. In comparison with reference monitored PM2.5 levels, it was found that PurpleAir PM2.5 concentrations were mostly higher. The most important reason for PurpleAir higher PM2.5 concentrations was the inclusion of moisture or water vapor as aerosol in contrast to measurements of PM2.5 excluding water content in FEM/FRM and non-FEM/FRM monitors. On long term assessment (2016-2020), R2 was between 0.54 and 0.86 at selected collocated PurpleAir and regulatory monitors for hourly PM2.5 concentrations. Past research studies have been conducted for mostly shorter time periods (<3-4 months) that resulted in higher R2 values between 0.80 to 0.98. This study aims to provide reasonable estimations of PM2.5 concentrations with high spatiotemporal resolutions based on statistical models using PurpleAir measurements. The methods of Kriging and IDW, geostatistical interpolation techniques, showed similar spatio-temporal patterns. Overall, this study revealed that low-cost, sensor based PurpleAir sensors could be effective and reliable tools for episodic and long-term ambient air quality monitoring.
Keywords
PurpleAir; low-cost sensor; PM2.5; IDW; Kriging
Subject
Environmental and Earth Sciences, Pollution
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
