Nitrosyl and Nitryl Chloride Formation in H2SO4/HNO3/H2O/HCl Solutions at 200 K     

T. J. Luick  R. W. Heckert  K. Schulz  R. S. Disselkamp 《Journal of Atmospheric Chemistry》1999,32(3):315-325

Infrared spectroscopy has been used to measure the vapor pressure of chlorine containing species generated from H2SO4/HNO3/H2O/HCl solutions at 200 K. The vapor pressure was observed to be a function of solution composition. Two solution compositions were investigated. One solution remained a liquid whereas the second solution was a mixed liquid and solid phase (an ice slurry). The liquid solution had a composition of 64.6 wt.% H2SO4/4.8 wt.% HNO3/30.1 wt.% H2O/0.5 wt.% HCl and produced only vapor phase HCl. The ice slurry solution had a composition of 76.6 wt.% H2SO4/3.0 wt.% HNO3/20.1 wt.% H2O/0.3 wt.% HCl and produced HCl, ClNO, and ClNO2 vapor phase components. The sulfuric acid, nitric acid, and water content of these solutions are representative of those present in polar stratospheric clouds (PSCs), however the HCl concentrations are much higher than present within these clouds. The partitioning of chlorine between vapor phase HCl (50%) and ClNO/ClNO2 (50%) for the ice slurry solution suggests a possible mechanism of halogen activation within PSCs. A reaction mechanism to model the observed chemistry is proposed.  相似文献   

Chlorine-hydrocarbon photochemistry in the marine troposphere and lower stratosphere     

H. B. Singh  J. F. Kasting 《Journal of Atmospheric Chemistry》1988,7(3):261-285

A one-dimensional photochemical model was used to explore the role of chlorine atoms in oxidizing methane and other nonmethane hydrocarbons (NMHCs) in the marine troposphere and lower stratosphere. Where appropriate, the model predictions were compared with available measurements. Cl atoms are predicted to be present in the marine troposphere at concentrations of approximately 10³ cm^-3, mostly as a consequence of the reaction of OH with HCl released from sea spray. Despite this low abundance, our results indicate that 20 to 40% of NMHC oxidation in the troposphere (0–10 km) and 40 to 90% of NMHC oxidation in the lower stratosphere (10–20 km) is caused by Cl atoms. At 15 km, NMHC-Cl reactions account for nearly 80% of the PAN produced.The model was also used to test the longstanding hypothesis that NOCl is an intermediate to HCl formation from sea salt aerosols. It was found that the NOCl concentration required (10 ppt) would be incompatible with field observations of reactive nitrogen and ozone abundance. Chlorine nitrate (ClONO₂) and methyl nitrate (CH₃ONO₂) were shown to be minor components of the total NO _y abundance. Heterogeneous reactions that might enhance photolysis of halocarbons or convert ClONO₂ to HOCl or Cl₂ were determined to be relatively unimportant sources of Cl atoms. Specific and reliable measurements of HCl and other reactive chlorine species are needed to better assess their role in tropospheric chemistry.  相似文献