Uptake of HNO₃ on Aviation Kerosene and Aircraft Engine Soot: Influences of H₂O or/and H₂SO₄

The uptake of HNO₃ on aviation kerosene soot (TC-1 soot) was studied in the absence and presence of water vapor at 295 and 243 K. The influence of H₂SO₄ coating of the TC-1 soot surface on HNO₃ uptake was also investigated. Only reversible uptake of HNO₃ was observed. HONO and NO₂, potential products of reactive uptake of HNO₃, were not observed under any conditions studied here. The uptake of nitric acid increased slightly with relative humidity (RH). Coating of the TC-1 soot surface with sulfuric acid decreased the uptake of HNO₃ and did not lead to displacement of H₂SO₄ from the soot surface. A limited set of measurements was carried out on soot generated by aircraft engine combustor (E-soot) with results similar to those on TC-1 soot. The influence of water on HNO₃ uptake on E-soot appeared to be more pronounced than on TC-1 soot. Our results suggest that HNO₃ loss in the upper troposphere due to soot is not significant except perhaps in aircraft exhaust plumes. Our results also suggest that HNO₃ is not converted to either NO₂ or HONO upon its uptake on soot in the atmosphere