Reactive and nonreactive uptake on hydrocarbon soot: HNO₃, O₃, and N₂O₅

The reactive and physical uptakes of HNO 3 , O 3 , and N 2 O 5 were examined on hydrocarbon soot by using a flow tube equipped with a chemical ionization mass spectrometer. The uptake of HNO 3 at 298 K was found to be reversible, and it did not produce NO 2 or NO; i.e., HNO 3 was not reduced. The uptake of O 3 on to soot was measured at 298 and 253 K and found to be small when the surface area of the soot was taken into account. We conclude that neither the HNO 3 nor the O 3 reaction on soot has much impact on the atmosphere. We observed the production of gas phase NO 2 from the uptake of N 2 O 5 on the soot surface with an efficiency of close to unity. It was concluded that the uptake of N 2 O 5 on soot is reactive. The implications of the N 2 O 5 reaction on soot to the atmosphere are not clear, because not all the products of this reactive uptake have been identified