10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Field Validation of a Low-Cost Integrated PM2.5 and Aerosol Optical Depth Monitor
ERIC WENDT, Jessica Tryner, Christian L'Orange, Bonne Ford, Casey Quinn, John Mehaffy, Jeffrey R. Pierce, Shantanu Jathar, Dan Miller-Lionberg, John Volckens, Colorado State University
Abstract Number: 1089 Working Group: Low-Cost and Portable Sensors
Abstract Atmospheric particulate matter smaller than 2.5 microns in diameter (PM2.5) impacts public health, the environment, and the climate. Reliable estimates of health and climate impacts require accurate measurements of PM2.5 at a global scale. Satellite-based measurements of Aerosol Optical Depth (AOD) may be used to quantify surface-level PM2.5 concentrations if the AOD:PM2.5 ratio is well constrained. These satellite-based measurements provide estimates of PM2.5 concentrations in regions where surface PM2.5 monitors are unavailable, but the AOD:PM2.5 ratio used for these predictions is subject to ongoing inquiry. Spatially dense ground-based networks of accurate co-located AOD and PM2.5 measurements are necessary to better define the AOD:PM2.5 ratio. However, the lack of an integrated PM2.5 and AOD monitor combined with the high cost ($10,000 - $45,000) of separate monitors has prevented such a network from being actualized.
We have developed a compact, low-cost (<$850) monitor capable of simultaneous measurement of AOD (at 440, 520, 680 and 870nm), filter-based PM2.5 concentration, and real-time PM2.5 concentration. The monitor’s small size, durability, low cost, and robust measurement capability circumvent some of the prior barriers to attaining a spatially dense distribution of measurements. Here we present the results of a field validation campaign spanning the latter half of 2017. The campaign consisted of a series of co-location studies where AOD and PM2.5 measurements were independently validated relative to reference monitors. The AOD sensors were evaluated against two AOD monitors in the Aerosol Robotics Network (AERONET). A total of 130 concurrent co-located measurements were made at each of the 4 wavelengths. The mean absolute error was 0.0079 AOD units (across all wavelengths), yielding an average relative error of 10%. Filter-based gravimetric sampling capability was evaluated against EPA Federal Reference Methods (FRMs) in a series of 39 paired (48-hr) samples. Average 48 hour concentrations examined ranged from 3.9 to 12.4 ug/m3. Strong agreement was found between the monitor gravimetric PM2.5 and the FRM measurements. The mean absolute error was 0.83 µg/m3 corresponding with an average relative error of 8%. The real-time sensor included in the monitor was evaluated against a real-time Federal Equivalent Method monitor (GRIMM model EDM 180). Close agreement was observed after real-time measurements were corrected to the filter measurements. These field validation results for this novel monitor demonstrate that AOD and PM2.5 can be accurately measured for the evaluation of AOD:PM2.5 ratios.