Procedures for estimating atmospheric deposition properties of organic chemicals

• Published in: Water, air, and soil pollution air, and soil pollution, 1984, Vol.21 (1/4), p.247-260
• Main Authors: Tucker, W.A, Preston, A.L
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; environmental degradation; Exact sciences and technology; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; waste management
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/BF00163628

A rationale for procedures to estimate the climatological means 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 soley by particle size, and methods for estimating the particle size are presented. Dry deposition velocity for the vapor fraction is derived by semiempirical analysis, and 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 mangitude of the measured values.