Evaluation and calibration of Aeroqual series 500 portable gas sensors for accurate measurement of ambient ozone and nitrogen dioxide

摘要

Low-power, and relatively low-cost, gas sensors have potential to improve understanding of intra-urban air pollution variation by enabling data capture over wider networks than is possible with 'traditional' reference analysers. We evaluated an Aeroqual Ltd. Series 500 semiconducting metal oxide O_3 and an electrochemical NO_2 sensor against UK national network reference analysers for more than 2 months at an urban background site in central Edinburgh. Hourly-average Aeroqual O_3 sensor observations were highly correlated (R~2 = 0.91) and of similar magnitude to observations from the UV-absorption reference O_3 analyser. The Aeroqual NO_2 sensor observations correlated poorly with the reference chem-iluminescence NO_2 analyser (R~2 = 0.02), but the deviations between Aeroqual and reference analyser values ([NO_2]_(Aeroq) - [NO_2]_(ref)) were highly significantly correlated with concurrent Aeroqual O_3 sensor observations [O_3]_(Aeroq·) This permitted effective linear calibration of the [NO_2]_(Aeroq) data, evaluated using 'hold out' subsets of the data (R~2 ≥ 0.85). These field observations under temperate environmental conditions suggest that the Aeroqual Series 500 NO_2 and O_3 monitors have good potential to be useful ambient air monitoring instruments in urban environments provided that the O_3 and NO_2 gas sensors are calibrated against reference analysers and deployed in parallel.