SOsub2/sub oxidation products other than Hsub2/subSOsub4/sub as a trigger of new particle formation. Part 2: Comparison of ambient and laboratory measurements, and atmospheric implications

摘要

Atmospheric new particle formation is generally thought to occur due tohomogeneous or ion-induced nucleation of sulphuric acid. We compare ambientnucleation rates with laboratory data from nucleation experiments involvingeither sulphuric acid or oxidized SO₂. Atmospheric nucleation occurs atH₂SO₄ concentrations 2–4 orders of magnitude lower than binary orternary nucleation rates of H₂SO₄ produced from a liquidreservoir, and atmospheric H₂SO₄ concentrations are very wellreplicated in the SO₂ oxidation experiments. We hypothesize thesefeatures to be due to the formation of free HSO₅ radicals in pace withH₂SO₄ during the SO₂ oxidation. We suggest that attemperatures above ~250 K these radicals produce nuclei of newaerosols much more efficiently than H₂SO₄. These nuclei areactivated to further growth by H₂SO₄ and possibly other tracespecies. However, at lower temperatures the atmospheric relative acidity ishigh enough for the H₂SO₄–H₂O nucleation to dominate.