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Performance of a Hybrid Lower-Cost PM Monitor in West Africa
JULIEN BAHINO, Michael R. Giordano, Eben Cross, James Nimo, Allison Hughes, Emmanuel Appoh, Christian Sewor, Kofi Amegah, Daniel Westervelt, Isaiah Tuolienuo, Melanie A Jackson, Stefani Penn, Rob Pinder, Arsene Ochou, Veronique Yoboue, Matthias Beekmann, R. Subramanian, OSU-EFLUVE, LISA/CNRS, UPEC, ENPC, UP
Abstract Number: 486
Working Group: Instrumentation and Methods
Abstract
Particulate matter (PM) low-cost sensors (LCS) are widely used to monitor air quality in regions where no reference monitors are available. Nephelometric LCS devices like the Plantower (used in PurpleAir devices) are insensitive to size distribution, as shown in multiple published laboratory studies. In areas where either resuspended or desert dust are significant contributors to ambient aerosol, nephelometric LCS devices can misattribute PM2.5-10 to PM2.5. Lower-cost optical particle sizers like the Alphasense OPC-N3 claim to measure and size particles up to 40 μm in diameter, making them candidates for lower-cost sensing of dust. But they do not report aerosol sizes below 350 nm. At the same time, published laboratory studies have shown that nephelometric LCS devices respond to 100-200 nm particles, even if the manufacturer’s stated detection limit is higher. Hence, a new alternative is the combined use of nephelometric LCS and OPCs, as in the Quant-AQ Modulair PM sensor.
In April 2021, we deployed five Modulair PM units in Ghana and Côte d’Ivoire. In Accra, Ghana, two sensors are collocated with the Ghana EPA’s Teledyne T640 monitor (PM2.5 and PM10) located at the University of Ghana, and one with the US embassy BAM (PM2.5). In Côte d’Ivoire, the Modulair units are collocated with a BAM-1022 (PM2.5) at the Université Félix Houphouët-Boigny, Abidjan, and with a TEOM (PM10) at Lamto, a remote location. Preliminary results from Accra indicate decent performance for PM2.5 using just the as-reported data, while the sensor performance for PM10 is weaker and needs to be corrected. We shall present results on the performance of the sensors across West Africa, corrections for the sensors, and the ability of this new lower-cost device to distinguish between PM2.5 and PM10 in equatorial and dust-influenced climates.