Stationary and portable multipollutant monitors for high-spatiotemporal-resolution air quality studies including online calibration

The distribution and dynamics of atmospheric pol-lutants are spatiotemporally heterogeneous due to variability in emissions, transport, chemistry, and deposition. To under-stand these processes at high spatiotemporal resolution and their implications for air quality and personal exposure, we present custom, low-cost air quality monitors that measure concentrations of contaminants relevant to human health and climate, including gases (e.g., O-3, NO, NO2, CO, CO2, CH4, and SO2) and size-resolved (0.3-10 mu m) particulate matter. The devices transmit sensor data and location via cellular communications and are capable of providing concentration data down to second-level temporal resolution. We produce two models: one designed for stationary (or mobile platform) operation and a wearable, portable model for directly mea-suring personal exposure in the breathing zone. To address persistent problems with sensor drift and environmental sen-sitivities (e.g., relative humidity and temperature), we present the first online calibration system designed specifically for low-cost air quality sensors to calibrate zero and span con-centrations at hourly to weekly intervals. Monitors are tested and validated in a number of environments across multi-ple outdoor and indoor sites in New Haven, CT; Baltimore, MD; and New York City. The evaluated pollutants (O-3, NO2, NO, CO, CO2, and PM2.5) performed well against reference instrumentation (e.g., r = 0.66-0.98) in urban field evaluations with fast e-folding response times (< 1 min), making them suitable for both large-scale network deployments and smaller-scale targeted experiments at a wide range of temporal resolutions. We also provide a discussion of best practices on monitor design, construction, systematic testing, and deployment.

Automated summary

Custom, low-cost air quality monitors were developed to measure concentrations of contaminants relevant to human health and climate, addressing issues such as pollutant heterogeneity and environmental sensitivities. The monitors performed well in various environments, showing potential for both large-scale network deployments and targeted experiments at different temporal resolutions.