The impact of cloud chemistry on photochemical oxidant formation

Conference · Sun Jan 01 04:00:00 EST 1984 · Proc., Annu. Meet., Air Pollut. Control Assoc.; (United States)

OSTI ID:5822212

Seigneur, C; Saxena, P

This paper presents a mathematical model of the cloud chemistry of photochemical oxidant formation. The model provides a detailed treatment of gas-phase chemistry, gas-phase/liquid-phase interaction, and liquid-phase chemistry. Model calculations conducted for a three-hour period showed that O/sub 3/ formation occurs more slowly in clouds than in a cloud-free atmosphere for the following reasons: photolysis rates within the cloud are lower; radicals are scavenged by cloud droplets; and aldehydes, which are a main source of HO/sub 2/ radicals in the gas phase, are highly soluble. The aqueous chemistry of O/sub 3/ does not affect its gas-phase concentration because of its low solubility and low aqueous reaction rates at pH <4. Cloud pH has little effect on O/sub 3/ formation. It is clear that the inclusion of cloud chemistry is necessary to accurately model photochemical oxidant formation. Concentrations of O/sub 3/ appear to be very sensitive to cloud transmissivity, efficiency of radical scavenging by cloud droplets, and droplet radius. These last two parameters directly affect the rate of radical scavenging and are therefore related. Development of mathematical models to simulate the chemistry of photochemical oxidant formation in clouds should take into account these important parameters.

• Research Organization: Systems Applications, Inc., San Rafael, CA
• OSTI ID: 5822212
• Report Number(s): CONF-840612-
• Conference Information: Journal Name: Proc., Annu. Meet., Air Pollut. Control Assoc.; (United States) Journal Volume: 6
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring &amp; Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ALDEHYDES
ATMOSPHERIC CHEMISTRY
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CLOUDS
DECOMPOSITION
DROPLETS
KINETICS
MATHEMATICAL MODELS
ORGANIC COMPOUNDS
OZONE
PARTICLES
PH VALUE
PHASE STUDIES
PHOTOCHEMICAL OXIDANTS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
QUANTITY RATIO
RADICALS
REACTION KINETICS
SCAVENGING
SOLUBILITY