Field Test of Several Low-Cost Particulate Matter Sensors in High and Low Concentration Urban Environments

Detailed quantification of the spatial and temporal variability of ambient fine particulate matter (PM_2.5) has, to date, been limited due to the cost and logistics involved with traditional monitoring approaches. New miniaturized particle sensors are a potential strategy to gather more time- and spatially-resolved data, to address data gaps in regions with limited monitoring and to address important air quality research priorities in a more cost-effective manner. This work presents field evaluations and lab testing of three models of low-cost (< $200) PM sensors (SHINYEI: models PPD42NS, PPD20V, PPD60PV) in three locations: urban background (average PM_2.5: 8 microg m^-3) and roadside in Atlanta, Georgia, USA (average PM_2.5: 21 microg m^-3), and a location with higher ambient concentrations in Hyderabad, India (average PM_2.5: 72 microg m^-3). Sensor measurements were compared against reference monitors in the lab using one-minute averages and in field locations using one-hour averages. At the Atlanta sites the sensors were weakly correlated with a tapered element oscillating microbalance (TEOM) at best (R² ≤ 0.30). In Hyderabad, the PPD20V sensors had the highest correlation with the environmental beta attenuation monitor (E-BAM) (R² > 0.80), however the same sensors had poor agreement if the comparison was restricted to lower concentrations (R² = ~0, < 40 microg m^-3). The results of this work indicate the potential usefulness of these sensors, including the PPD20V, for higher concentration applications (< ~250 microg m^-3). These field- testing results provide important insights into the varying performance of low-cost PM sensors under highly contrasting atmospheric conditions. The inconsistent performance results underscore the need for rigorous evaluation of optical particle sensors in the laboratory and in diverse field environments.