A five-channel cavity ring-down spectrometer for the detection of NO 2, NO 3, N 2O 5, total peroxy nitrates and total alkyl nitrates
We report the characteristics and performance of a newly developed five-channel cavity ring-down spectrometer to detect NO 3, N 2O 5, NO 2, total peroxy nitrates (ΣPNs) and total alkyl nitrates (ΣANs). NO 3 and NO 2 are detected directly at 662 and 405 nm, respectively. N 2O 5 is measured as NO 3 after thermal decomposition at 383 K. PNs and ANs are detected as NO 2 after thermal decomposition at 448 and 648 K. We describe details of the instrument construction and operation as well as the results of extensive laboratory experiments that quantify the chemical and optical interferences that lead to biases in the measured mixing ratios, in particular involving the reactions of organic radical fragments following thermal dissociation of PNs and ANs. Finally, we present data obtained during the first field deployment of the instrument in July 2015.