Technical note: Gas-phase nitrate radical generation via irradiation of aerated ceric ammonium nitrate mixtures

We present a novel photolytic source of gas-phase inline-formulaNO₃ suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize inline-formulaNO₂ inline-formula+ inline-formulaO₃ reactions and/or thermal dissociation of dinitrogen pentoxide (inline-formulaN₂O₅). The method generates inline-formulaNO₃ via irradiation of aerated aqueous solutions of ceric ammonium nitrate (CAN, inline-formula(NH₄)₂Ce(NO₃)₆) and nitric acid (inline-formulaHNO₃) or sodium nitrate (inline-formulaNaNO₃). We present experimental and model characterization of the inline-formulaNO₃ formation potential of irradiated CAN inline-formula $M12inlinescrollmathml/$ 8pt14ptsvg-formulamathimg6bfc4ae3491d603d986b6e1d0e6866cf acp-23-13869-2023-ie00001.svg8pt14ptacp-23-13869-2023-ie00001.png  inline-formulaHNO₃ and CAN inline-formula $M14inlinescrollmathml/$ 8pt14ptsvg-formulamathimg539a58614ea8688159b8effbc6d3da8d acp-23-13869-2023-ie00002.svg8pt14ptacp-23-13869-2023-ie00002.png  inline-formulaNaNO₃ mixtures containing [CAN] inline-formula= 10inline-formula⁻³ to 1.0 M, [inline-formulaHNO₃] inline-formula= 1.0 to 6.0 M, [inline-formulaNaNO₃] inline-formula= 1.0 to 4.8 M, photon fluxes (inline-formulaI) ranging from 6.9 inline-formula× 10inline-formula¹⁴ to 1.0 inline-formula× 10inline-formula¹⁶ photons cminline-formula⁻² sinline-formula⁻¹, and irradiation wavelengths ranging from 254 to 421 nm. inline-formulaNO₃ mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [inline-formulaNO₃] was achieved using [inline-formulaHNO₃] inline-formula≈ 3.0 to 6.0 M and UVA radiation (inline-formulaλ_max⁡ inline-formula= 369 nm) in CAN inline-formula $M35inlinescrollmathml/$ 8pt14ptsvg-formulamathimg07d7a1dd05fd1823c5d4d7644fe5a26c acp-23-13869-2023-ie00003.svg8pt14ptacp-23-13869-2023-ie00003.png  inline-formulaHNO₃ mixtures or [inline-formulaNaNO₃] inline-formula≥ 1.0 M and UVC radiation (inline-formulaλ_max⁡ inline-formula= 254 nm) in CAN inline-formula $M41inlinescrollmathml/$ 8pt14ptsvg-formulamathimgdec69c2f61a2c3df83845e73f901bed1 acp-23-13869-2023-ie00004.svg8pt14ptacp-23-13869-2023-ie00004.png  inline-formulaNaNO₃ mixtures. Other reactive nitrogen (inline-formulaNO₂, inline-formulaN₂O₄, inline-formulaN₂O₅, inline-formulaN₂O₆, inline-formulaHNO₂, inline-formulaHNO₃, inline-formulaHNO₄) and reactive oxygen (inline-formulaHO₂, inline-formulaH₂O₂) species obtained from the irradiation of ceric nitrate mixtures were measured using a inline-formulaNO_x analyzer and an iodide-adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of inline-formulaNO₃-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) from the inline-formulaβ-pinene inline-formula+ inline-formulaNO₃ reaction using a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to the HR-ToF-CIMS.