Performance of Nephelometric and OPC-based Lower-Cost Monitors in Dusty and Desert-Influenced Environments

R. SUBRAMANIAN, Mohammed Ayoub, Shamjad Moosakutty, Rami Alfarra, Qatar Environment & Energy Research Institute

     Abstract Number: 337
     Working Group: Instrumentation and Methods

Abstract
Air pollution is the largest environmental health risk, with an estimated toll of almost 7 million deaths in 2019 (HEI State of Global Air). Fine particulate matter mass (PM_2.5) is a key contributing pollutant. In rapidly growing middle-eastern cities, PM₁₀ from natural and anthropogenic sources is also critical. QEERI operates a network of six reference-grade stations across Greater Doha including three that monitor PM₁₀, but micro-environments such as traffic, industrial activity, and construction can result in hyperlocal pollution not captured by these reference stations. Lower-cost sensors can fill this data gap, enabling high spatial and temporal resolution measurements of air pollution. We have conducted extensive field testing of a variety of lower-cost devices for PM measurements across Doha. We find that sensor design can fatally compromise product performance for super-micron aerosol, with implications for accurate monitoring of both PM_2.5 and PM₁₀. Nephelometric PM sensors (e.g. Plantower-based) significantly underestimate PM_2.5 mass during dust events and are poorly correlated with reference beta attenuation monitors. Sensors using optical particle counters (OPC only or hybrid nephelometric/OPC sensors) perform relatively better but need to be properly field-characterized. As seen elsewhere, aerosol hygroscopic growth can also impact sensor performance. Well-characterized sensors have been effectively used to detect the impact of hyperlocal air pollution, e.g. from construction dust piles. We shall discuss these results and their implications for air quality monitoring in Qatar and similar regions especially around major athletic events.