UC Merced Undergraduate Research Journal

Fine particulate matter (PM2.5) exhibits pronounced spatial variability even across the scale of a university campus and readily infiltrates the lungs and bloodstream, exacerbating respiratory and cardiovascular health burdens. Recognizing this heterogeneity is essential for accurately characterizing exposure, particularly for the student population that may be unaware of its adverse impacts. The San Joaquin Valley, home to UC Merced, remains out of compliance with federal PM2.5 and ozone standards and has received an F grade from the American Lung Association. However, campus air quality is monitored by only one fixed PurpleAir sensor at the Science and Engineering 2 Building (SE2), which may not capture local PM2.5 variability. To address this gap, we undertook a mobile monitoring campaign during the 2025 spring term using a handheld EXTECH VPC300. Hundreds of geo-referenced readings were gathered along walkways, parking areas, construction zones, and other busy sites, then compared with daily values from the fixed PurpleAir sensor. The handheld and PurpleAir measurements exhibited similar day-to-day and weekly trends, indicating that the fixed PurpleAir unit effectively captures overall temporal variations in PM2.5. Midweek elevations compared to weekends likely reflect increased campus activity, such as traffic, construction, and maintenance. However, the fixed PurpleAir sensor cannot capture elevated PM2.5 near parking areas and construction zones detected by the handheld device. These findings suggest that while a single monitor can track general trends, a distributed network of low-cost sensors is needed to capture local exposure differences and guide targeted mitigation for the UC Merced community.