Comprehensive measurements of speciated reactive nitrogen NOy and non-methane volatile organic compounds in Tokyo

In Japan, concentrations of precursors of photochemical oxidants such as nitrogen oxides (NOx) and non-methane hydrocarbons (NMHCs) are decreasing year by year, but an improvement regarding photochemical oxidants is recently stagnant. To elucidate the reason, we have planned seasonal intensive observations in Tokyo, in which comprehensive measurements of speciated reactive nitrogen NOy and non-methane volatile organic compounds are performed. In summer of 2022, the observation was carried out at a campus of Tokyo Metropolitan University, a suburban area of Tokyo. In the intensive observation, NO, NO₂, ΣPANs, ΣONs, HONO, HNO₃, H₂O₂, SO₂, O₃, NH₃, 28 NMHCs, and 10 oxygenated volatile organic compounds (OVOCs) were measured simultaneously. The ΣPANs and ΣONs were measured by thermal dissociation-cavity attenuated phase shift (CAPS) spectroscopy. The HONO, HNO₃, and H₂O₂ were measured by negative ion chemical ionization mass spectrometry using I⁻·(H₂O)_n as the reagent ion. The NMHCs, OVOCs and NH₃ were measured by selected ion flow tube mass spectrometry and the data of NMHCs were compared and corrected with the data from gas chromatography/flame ionization detector (GC/FID). The ozone formation in Tokyo will be discussed.