Volatilization Rates of Organic Chemicals of Public Health Concern

Abstract

Liquid film coefficients of ethylene gas, KL, are determined from data on ethylene and rhodamine WT dye concentration distributions, which were collected in shallow streams and rivers located in Southern Ontario, Canada. Relationships among KL, river channel hydraulic characteristics and chemical properties of organic compounds have been developed through dimensional analysis using the Buckingham π‐Theorem. A sensitivity analysis of various parameters on KL has been carried out. A statistical relationship developed by Rathbun and Tai (1982) has been found to underestimate KL values for the Southern Ontario streams and rivers. An evaluation of the theoretical relationships between KL and molecular properties (critical volumes and molecular weights) using experimental data reported in the literature has revealed that the relation between KL and critical volume is suitable to calculate KL values for highly volatile organic chemicals using the known KL values of ethylene gas or other compounds (e.g., propane, benzene); however, for moderate and low volatile compounds, no relationships could be obtained from the available data. The computation of KL for a given organic compound using the relationships developed in this study is outlined in a step‐by‐step procedure. An example illustrates the various computations involved. In general, the method is applicable to volatile compounds with Henry's law constants greater than 10-3atm‐m3/mol.