Theory of pollution washdown based on theoretical and experimental scavenging studies
A fundamental theory which describes the absorption of trace gases into freely falling raindrops is presented. This theory is based on the convective diffusion equation and modified or verified according to results of detailed experimental studies of SO/sub 2/ absorption into raindrops. These experiments were performed utilizing the UCLA precipitation shaft. For drops with equivalent radii less than 500 ..mu..m, experimental results agreed favorably with theoretical predictions. For drops smaller than this, steady state convection and molecular diffusion appear to be the two dominant means of trace gas transport within a falling drop. Utilizing a modified theory which incorporated internal ventilation effect, a mass conserving model of pollution washdown by rainfall was developed. Testing this model on a gaussian plume of SO/sub 2/ at a height of 200 m, sensitivity studies were performed to determine the important factors which govern the rate of pollution washdown. It was found that the washout rate (% of trace gas in the layer removed by a millimeter of rain) was inversely proportional to the height, thickness, and peak concentration in the layer. Rainfall composed of larger drops (corresponding to a higher rainfall rate) was slightly less efficient at removing pollutant for the same amount of rain. The rate of sulfur oxidation within the rain was found to be one of the most important parameters which governs the overall washout rate.
- OSTI ID:
- 6632326
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACID RAIN
SULFUR DIOXIDE
WASHOUT
ABSORPTION
AIR POLLUTION CONTROL
DROPLETS
PRECIPITATION SCAVENGING
RAIN
REMOVAL
ATMOSPHERIC PRECIPITATIONS
CHALCOGENIDES
CONTROL
OXIDES
OXYGEN COMPOUNDS
PARTICLES
POLLUTION CONTROL
SEPARATION PROCESSES
SULFUR COMPOUNDS
SULFUR OXIDES
500200* - Environment
Atmospheric- Chemicals Monitoring & Transport- (-1989)