Laboratory studies of H₂SO₄/H₂O binary homogeneous nucleation from the SO₂+OH reaction: evaluation of the experimental setup and preliminary results

L.-H. Young (1, 2) , D. R. Benson (1) , F. R. Kameel (1) , S.-H. Lee (1)

1 Department of Chemistry
2 China Medical University

We have developed a new laboratory nucleation setup to study binary homogeneous nucleation (BHN) of sulphuric acid and water (H₂SO₄/H₂O). Here we provide a detailed evaluation of this new experimental setup and also discuss our preliminary results by comparing with other laboratory studies. H₂SO₄ is produced from the SO₂+OH ?HSO₃ reaction and OH radicals are produced from water vapor UV absorption. The residual H₂SO₄ concentrations ([H₂SO₄]) are measured at the end of the fast flow nucleation reactor with a chemical ionization mass spectrometer. The measured BHN rates (J) ranged from 0.02 and 550 cm^?3 s^?1 at the residual [H₂SO₄] from 10⁸ to 10¹⁰ cm^?3, a temperature of 288 K and relative humidity (RH) from 6 to 23%; J increased with increasing [H₂SO₄] and RH. J also showed a power dependence on [H₂SO₄] with the exponential power of 3 to 8. These results are consistent with other laboratory studies under similar [H₂SO₄] and RH, but different from atmospheric field observations which showed that particle number concentrations are often linearly dependent on [H₂SO₄]. Both particle sizes and number concentrations increased with increasing [H₂SO₄], RH, and nucleation time, consistent with the predictions from nucleation theories. Particle growth rates were estimated between 28 to 127 nm h^?1, much higher than those seen from atmospheric field observations, because of the higher [H₂SO₄] used in our study. While these experimental results demonstrate a validation of our laboratory setup, there are also technical difficulties associated with nucleation studies, including wall loss and H₂SO₄ measurements.

Domaines: Océan, Atmosphère

L.-H. Young, D. R. Benson, F. R. Kameel, S.-H. Lee. Laboratory studies of H₂SO₄/H₂O binary homogeneous nucleation from the SO₂+OH reaction: evaluation of the experimental setup and preliminary results. Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.6903-6947. ⟨hal-00304083⟩