Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia

T. Kurtén (1) , V. Loukonen (1) , H. Vehkamäki (1) , M. Kulmala (1)

1 Division of Atmospheric Sciences

We have studied the structure and formation thermodynamics of dimer clusters containing H₂SO₄ or HSO₄^? together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine ? H₂SO₄ complexes is significantly stronger than that of NH₃?H₂SO₄, while most amine ? HSO₄^? complexes are only somewhat more strongly bound than NH₃?HSO₄^?. Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H₂SO₄ molecules or one H₂SO₄ molecule and one HSO₄^? ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H₂SO₄ co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric acid-water nucleation in the atmosphere.

Domaines: Océan, Atmosphère

T. Kurtén, V. Loukonen, H. Vehkamäki, M. Kulmala. Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia. Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.7455-7476. ⟨hal-00304107⟩