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 (ΣPNs, RO 2 NO 2), total alkyl nitrates (ΣANs, RONO 2), and NO 2 was presented in this work. ΣPNs and ΣANs were detected as NO 2 with the CRDS instrument after thermal dissociation. PNs and ANs completely dissociated at 180 °C and 360 °C, with conversion efficiencies of 96 % and 99 %, respectively. The effects of NO 2 and NO on measurement in different temperatures and two types of thermal dissociation inlet (TDI) were further explored. The influence of ambient NO 2 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 NO 2 in the three channels was tested, which achieved good agreement. The detection limits of the TD-CRDS instrument for NO 2 , ΣPNs, and ΣANs were determined as 6.5, 6.8, and 8.6 pptv (10 s, 1σ), 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 ΣPNs and ΣANs. [Display omitted] • A newly developed three-channel TD-CRDS instrument could simultaneously quantify ΣPNs, ΣANs, and NO 2. • The effects of NO 2 and NO on the measurements of PNs and ANs greatly ameliorated in the improved TDI. • The dissociation of PNs at 360 °C essentially did not affect the measurement of ANs. [ABSTRACT FROM AUTHOR]