Daily Estimation of Ground-Level PM2.5 Concentrations over Beijing Using 3 km Resolution MODIS AOD

• Published in: Environmental science & technology 2015-10, Vol.49 (20), p.12280-12288
• Main Authors: Xie, Yuanyu, Wang, Yuxuan, Zhang, Kai, Dong, Wenhao, Lv, Baolei, Bai, Yuqi
• Format: Article
• Language: English
• Subjects: Aerosols - analysis; Beijing; Calibration; Humans; Linear Models; Models, Theoretical; Optical Phenomena; Particle Size; Particulate Matter - analysis; Regression Analysis; Reproducibility of Results; Spectrum Analysis; Time Factors; Uncertainty
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.5b01413

Estimating exposures to PM2.5 within urban areas requires surface PM2.5 concentrations at high temporal and spatial resolutions. We developed a mixed effects model to derive daily estimations of surface PM2.5 levels in Beijing, using the 3 km resolution satellite aerosol optical depth (AOD) calibrated daily by the newly available high-density surface measurements. The mixed effects model accounts for daily variations of AOD-PM2.5 relationships and shows good performance in model predictions (R 2 of 0.81–0.83) and cross-validations (R 2 of 0.75–0.79). Satellite derived population-weighted mean PM2.5 for Beijing was 51.2 μg/m3 over the study period (Mar 2013 to Apr 2014), 46% higher than China’s annual-mean PM2.5 standard of 35 μg/m3. We estimated that more than 19.2 million people (98% of Beijing’s population) are exposed to harmful level of long-term PM2.5 pollution. During 25% of the days with model data, the population-weighted mean PM2.5 exceeded China’s daily PM2.5 standard of 75 μg/m3. Predicted high-resolution daily PM2.5 maps are useful to identify pollution “hot spots” and estimate short- and long-term exposure. We further demonstrated that a good calibration of the satellite data requires a relatively large number of ground-level PM2.5 monitoring sites and more are still needed in Beijing.