Phase transformations in sulfuric acid aerosols: Implications for stratospheric ozone depletion

• Main Authors: Dan G. Imre, Jun Xu, Anthony C. Tridico
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.490.3547; http://www.ecd.bnl.gov/pubs/BNL62996R.pdf

Abstract. Activation reactions of benign chlorine species (HC1, C1ONO2) on aerosols in the winter polar stratosphere s t the stage for the spring-time catalytic destruction f ozone leading to the Antarctic ozone hole. Field observations have demonstratecl theexistence of both solid and liquid particles consisting ofH2SO 4, HNO 3, and H20. The exact fi'eezing conditions and final composition of the solid aerosols remain the subject of investigations. We present laboratory observations of isolated individual sulfiaric acid/water particles under stratospheric temperatures and water vapor pressures. Our experiments demonstrate hat this binary system would not fi'eeze unless temperatures were below the water-ice frost point. Upon fi'eezing, we observe H2SO4.SH20, not the generally invoked H2SO4.4H20. We suggest that the water-rich octahydrate phase is likely to be one of the high relative humidity forms which is efficient in chlorine activation.