New System for Measuring the Photochemical Ozone Production Rate in the Atmosphere.

We have developed a new system for measuring photochemical ozone production rates in the atmosphere. Specifically, the system measures the net photochemical oxidant (O: the sum of ozone (O) and nitrogen dioxide (NO)) production rates (P-L(O)). Measuring O avoids issues from perturbations to the photostationary states between nitrogen oxides (NO) and O. This system has "reaction" and "reference" chambers. Ambient air is introduced into both chambers, and O is photochemically produced in the reaction chamber and not generated in the reference chamber. Air from the chambers is alternately introduced into an NO-reaction (NO: nitric oxide) tube to convert O to NO, and then the O concentration is measured as NO using a laser-induced fluorescence technique. P-L(O) was obtained by dividing the difference in O concentrations between air samples from the two chambers by the mean residence time of the air in the reaction chamber. In this study, the P-L(O) measurement system was characterized, and the current detection limit of P-L(O) was determined to be 0.54 ppbv h with an integration time of 60 s (S/N = 2), assuming an ambient O concentration of 100 ppbv. Field measurements of P-L(O) were conducted using the system at a remote forest location.