HNO3 losses within the cyclone inlet of a diffusion-denuder system under simulated marine environments

We evaluated the loss of HNO3 within a Teflon-coated aluminum cyclone of an annular diffusion denuder atmospheric sampling system (ADS) under simulated marine conditions. To simulate marine environment, the cyclones were pre-coated with NaCl aerosol droplets. Loss of vapor-phase HNO3 within the NaCl-coated cyclone was generally greater than 30% at relative humidities (RH) of 60 and 80% and as large as 67% when the cumulative HNO3 dosages were lower than 3 μg. In contrast, there was little loss of HNO3 (<8%) in cyclones with no NaCl coating at RHs ranging from 0 to 80%, at HNO3 air concentrations of 4.3±1.6 μg m−3, and at cumulative HNO3 dosages of greater than 5 μg. However, at lower HNO3 cumulative dosages (<3 μg), losses in the non-coated cyclones were strongly influenced by RH, ranging from 9% in dry air to 58% at 80% RH. The enhanced loss of HNO3 in the NaCl-coated cyclone was most likely caused by the reaction between HNO3 and NaCl on the cyclone wall.