Utilization of scattering and absorption-based particulate matter sensors in the environment impacted by residential wood combustion
Joel Kuula, Milla Friman, Aku Helin, Jarkko V. Niemi, Minna Aurela, Hilkka Timonen, Sanna Saarikoski
Abstract
Residential wood combustion, which is characterized by incomplete combustion, is a common source of particulate matter in suburban areas. This study investigated the usability of three different scattering-based particulate matter (PM) sensors and an absorption-based black carbon (BC) sensor in an environment impacted by wood combustion emissions. The measurement campaign, which lasted approximately 10 weeks, was conducted during wintertime in a suburban detached housing area in Helsinki, Finland. The results indicated that the scattering-based sensors were better suited for the measurement of PM1 (R2: 0.94–0.97) than for the PM2.5 (R2: 0.75–0.87). Analysis of the different proportions of size fractions indicated this was due to the particle size discrimination characteristics of sensors. Furthermore, the sensor responses were affected by the BC to PM1 ratio. This was attributed to the changing optical properties of the measured aerosol; however, the effect was not consistent across all the 3 p.m. sensors. The absorption-based BC sensor exhibited very good performance (R2: 0.97–0.98) at 470 and 880 nm wavelengths, and the source apportionment (BC contributed to wood burning and fossil fuel combustion) results were comparable to that of the reference instrument. When sensor data was applied in practice, a case study demonstrated that a simultaneous use of PM1 and BC sensors enabled more sophisticated data analysis; episodes originating from local wood burning and long-range transported aerosols were distinguishable from each other due to their different BC to PM1 ratios. The evaluated sensors were shown to bring added value to residential area air quality assessments.