Integration of Low-Cost Sensors in Understanding the Impacts of Dust Events on Puerto Rico’s Air Quality

The Saharan Air Layer (SAL) is a mass of hot, dry, and dusty air that forms over the Sahara Desert propagating westward over the Atlantic Ocean. Saharan dust aerosol is most concentrated as coarse particulate matter greater than one micron in diameter, i.e. PM₁ to PM₁₀ (PM_c). Due to its geographical location, Puerto Rico is impacted by SAL during June to August, when SAL activity peaks. Despite its vulnerability, the existing air quality monitoring network faces limitations, especially in the distribution of PM₁₀ monitors and access to data. Nevertheless, low-cost sensors (LCS) for PM can provide monitoring opportunities and information to communities about their local air quality. Here we analyze how LCS can be utilized to enhance the characterization of major dust events in Puerto Rico. To address the observational gaps, we installed five MODULAIR-PM monitors in strategic locations across the island. Since these sensors use both a nephelometer-type optical sensor (Plantower PMS5003) and an optical particle counter (Alphasense OPC-N3) to quantify mass concentration and particle size, we compared readings to determine their strengths and weaknesses. Satellite imagery and HYSPLIT models were used to identify SAL summer 2023 events. Additionally, size distribution for these events, PM_2.5 chemical composition, and meteorological data were evaluated. Our initial findings reveal that higher concentrations of PM_c during dust events imply dust particle diameters are greater than 1µm, therefore nephelometer-type sensors are not useful to measure these aerosols, consistent with previous literature evaluations of Plantower. However, MOD-PM has a better ability to size particles and identify dust events. Around 80% of the PM_2.5 during dust events is composed of natural sources (dust, sea salt), highlighting the importance of understanding these aerosols and their associated connections with meteorology. Ongoing research aims to further explore the influence of meteorology on dust events and evaluate the relationship between MOD-PM and reference method monitor data. Overall, the integration of LCS can aid in the understanding of dust events on the island, help create a network of air quality sensors to address the lack of monitoring, and allow communities to make informed decisions regarding their local air quality.