Chlorine-hydrocarbon photochemistry in the marine troposphere and lower stratosphere

H. B. Singh, James Kasting

Research output: Contribution to journalArticle

197 Citations (Scopus)

Abstract

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 NOy 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.

Original languageEnglish (US)
Pages (from-to)261-285
Number of pages25
JournalJournal of Atmospheric Chemistry
Volume7
Issue number3
DOIs
StatePublished - Oct 1 1988

Fingerprint

nonmethane hydrocarbon
Upper atmosphere
Troposphere
Photochemical reactions
Chlorine
photochemistry
Hydrocarbons
stratosphere
chlorine
troposphere
hydrocarbon
Atoms
chlorine nitrate
Halocarbons
halocarbon
oxidation
Oxidation
Ozone
Methane
Photolysis

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Atmospheric Science

Cite this

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abstract = "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 NOy 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.",
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Chlorine-hydrocarbon photochemistry in the marine troposphere and lower stratosphere. / Singh, H. B.; Kasting, James.

In: Journal of Atmospheric Chemistry, Vol. 7, No. 3, 01.10.1988, p. 261-285.

Research output: Contribution to journalArticle

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