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

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.