Physical chemistry of the H[sub 2]SO[sub 4]/HNO[sub 3]/H[sub 2]O system: Implications for polar stratospheric clouds

Journal Article · Fri Sep 10 00:00:00 EDT 1993 · Science (Washington, D.C.); (United States)

DOI:https://doi.org/10.1126/science.261.5127.1418· OSTI ID:5246189

Molina, M J; Zhang, R; Wooldridge, P J; McMahon, J R; Kim, J E; Chang, H Y; Beyer, K D ^[1]

---

1. Massachusetts of Technology, Cambridge, MA (United States)

Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO[sub 3] hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H[sub 2]SO[sub 4]/H[sub 2]O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO[sub 3] vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO[sub 3] and H[sub 2]O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H[sub 2]SO[sub 4] solutions and on solid H[sub 2]SO[sub 4] hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles.

• OSTI ID: 5246189
• Journal Information: Science (Washington, D.C.); (United States), Journal Name: Science (Washington, D.C.); (United States) Vol. 261:5127; ISSN SCIEAS; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
AEROSOLS
CHEMICAL REACTIONS
CHEMISTRY
CHLORINE COMPOUNDS
CLOUDS
COLLOIDS
DISPERSIONS
EARTH ATMOSPHERE
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
LAYERS
LOSSES
NITRIC ACID
OXYGEN COMPOUNDS
OZONE LAYER
PHYSICAL CHEMISTRY
SOLS
STRATOSPHERE
SULFURIC ACID
SYNTHESIS
WATER