Laboratory-Measured Nucleation Rates of Sulfuric Acid and Water from the SO$_{2}$ + OH Reaction

We present results of the laboratory study of sulfuric acid-water binary nucleation system. H$_{2}$SO$_{4}$ was produced through the reaction of SO$_{2}$ + OH $\to$ HSO$_{3}$ in the presence of SO$_{2}$, OH, O$_{2}$, and H$_{2}$O in a fast flow reactor at 288 K and atmospheric pressure. OH was produced from the photolysis of water vapor. The power dependence of nucleation rate ($J)$ on sulfuric acid concentration ([H$_{2}$SO$_{4}$]) was 2 - 10 in the [H$_{2}$SO$_{4}$] range from 3$\times $10$^{6}$ - 1$\times$ 10$^{9}$ cm$^{-3}$. This power dependence increased with decreasing RH and increasing nucleation time. The power dependence of $J$ on RH was 10 - 15 for the RH values from 10 - 50{\%}. The measured aerosol sizes ranged from 4 - 20 nm. These aerosol sizes were larger for higher [H$_{2}$SO$_{4}$], higher RH, and higher nucleation times. The effects of RH on aerosol growth were also more pronounced at higher [H$_{2}$SO$_{4}$] and with higher nucleation times.