Procedures for estimating atmospheric deposition properties of organic chemicals

✍ Scribed by William A. Tucker; Alan L. Preston

• Publisher: Springer Netherlands
• Year: 1984
• Tongue: English
• Weight: 816 KB
• Volume: 21
• Category: Article
• ISSN: 0049-6979
• DOI: 10.1007/bf00163628

✦ Synopsis

A rationale for procedures to estimate the climatological mean dry deposition velocity and precipitation scavenging ratio of organic chemicals is developed. Both deposition parameters depend strongly on vapor pressure, as it affects the partitioning between vapor and sorbed phases. Separate formulae are presented for vapor and sorbed fractions using their mass-weighted average to describe the deposition parameters for the total airborne concentration. Deposition of sorbed fractions is controlled solely by particle size, and methods for estimating the particle size are presented. Dry deposition velocity for the vapor fraction is derived by semiempirical analysis, ~nd is found to depend on Henry's Law constant, molecular diffusion coefficients in air and water, and the chemical's reaction rate in water. Estimates of the dry deposition velocity for 5 chlorinated hydrocarbons are made and compared with observations. Estimates of the precipitation scavenging ratio are compared with observational data for 11 chlorinated or aromatic hydrocarbons. The estimates generally are within an order of magnitude of the measured values.