Bachner, Mathias

Fuchs, Hendrik

Kubik, Kamil

Schrade, Stephanie

Juelich Shared Electronic Resources

Characterisation and first application of a cavity ring-down instrument for measurements of NO3 and N2O5

Geophysical Research AbstractsVol. 16, EGU2014-10173, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Characterisation and first application of a cavity ring-down instrumentfor measurements of NO3 and N2O5Stephanie Schrade, Mathias Bachner, Kamil Kubik, and Hendrik FuchsForschungszentrum Jülich GmbH, IEK-8: Troposphäre, Germany (s.schrade@fz-juelich.de)A new instrument was built for atmospheric measurements using the cavity ringdown technique for a simultaneousmeasurement of nitrate radicals (NO3) and dinitrogen pentoxide (N2O5) using a red laser diode at 662 nm. Theinstrument consists of two channels: The inlet and the cavity of the first one is heated up to 120 ◦C to forcethe thermal equlibrium of N2O5 and NO3 to the side of NO3, so that this channel measures the sum NO3 andN2O5. The other channel stays at ambient temperature to measure NO3 only. To prevent aerosol extinction, a filteris installed upstream of the cavities. The detection limit is within the range of a few ppt at 1 s time resolution.Measurements have an accuracy of 15 %. Instrument losses were characterized by a titration method using theconversion of NO3 to NO2 by adding NO. Two addition points where chosen, right before and after the NO3intrument.The NO2 concentration was measured downstream of the instrument with another CRDS intrumentusing a blue laser diode at 405 nm. Estimated losses are within the range of 40 % due two a high point loss on theused filter housing. First application took place at the SAPHIR simulation chamber at Forschungszentrum JülichGmbH. Experiments were made by injecting known concentrations of NO2 and ozone into the dark chamber filledwith pure synthetic air to analyse the behavior of NO3 and N2O5 in the clean chamber. Possible losses wereestimated from the steady-state lifetime of NO3, which can be calculated from measured NO3, NO2 and ozoneconcentrations. Estimated lifetimes of NO3 and N2O5 were within the range of 19 min and 44 min, respetively.During futher experiments organic compounds (isoprene, β-pinene, limonene) were additionally injected, in orderto test the applicability of chamber experiments for the invertigation of oxidation processes by NO3.

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Characterisation and first application of a cavity ring-down instrument for measurements of NO3 and N2O5

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