A three-channel thermal dissociation cavity ring-down spectrometer for simultaneous measurement of ambient total peroxy nitrates, total alkyl nitrates, and NO2

A newly constructed thermal dissociation cavity ring-down spectrometer (TD-CRDS) for the simultaneous measurement of ambient total peroxy nitrates (EPNs, RO2NO2), total alkyl nitrates (EANs, RONO2), and NO2 was presented in this work. EPNs and EANs were detected as NO2 with the CRDS instrument after thermal dissociation. PNs and ANs completely dissociated at 180 degrees C and 360 degrees C, with conversion efficiencies of 96 % and 99 %, respectively. The effects of NO2 and NO on measurement in different temperatures and two types of thermal dissociation inlet (TDI) were further explored. The influence of ambient NO2 and NO on PNs and ANs in the improved TDI (TDI-2) was significantly improved. To further enhance the measurement accuracy, the consistency of the observed NO2 in the three channels was tested, which achieved good agreement. The detection limits of the TD-CRDS instrument for NO2, EPNs, and EANs were determined as 6.5, 6.8, and 8.6 pptv (10 s, 1a), respectively. Observations of PNs and ANs were conducted in a suburban site in Hefei, China, from September 2-30, 2021, using the TD-CRDS instrument, and the consecutive time series of PNs and ANs were derived, verifying the capability of the TD-CRDS instrument for continuous field observations of EPNs and EANs.