Development of a 443 nm diode laser-based differential photoacoustic spectrometer for simultaneous measurements of aerosol absorption and NO(2)

Cao, Yuan; Liu, Qiang; Wang, Ruifeng; Liu, Kun; Chen, Weidong; Wang, Guishi; Gao, Xiaoming

Measurement of ambient aerosol and nitrogen dioxide (NO(2)) is important as they are major pollutants from the burning of fossil fuel and biomass. In the present work, a differential photoacoustic spectrometer (D-PAS) was developed for simultaneous, online measurements of aerosol optical absorption and NO(2) concentration. A novel photoacoustic resonator was designed and employed in the D-PAS for controlling a large flow rate, improving response time, and keeping the flow noise at a low level. The detection limits of 1.0 Mm(−1) and 0.87 ppb for aerosol absorption and NO(2) concentration measurements were achieved with a lock-in amplifier time constant of 1 s. The D-PAS accuracy was demonstrated by performing a long-time, continuous measurement of aerosol, and NO(2) in ambient air. The measured results of NO(2) are consistent with the NOx analyzer and environmental monitoring station results.