Distribution of volatile organic contaminants between water and air

Abstract

Exchange of synthetic organic contaminants across the air-water interface is a significant process affecting the fate of the contaminants released into the environment. Benzene, toluene, trichloroethylene, and tetrachloroethylene were selected as typical contaminants in this study. The equilibrium distribution of the selected volatile organic compounds between air and water was simulated in the laboratory at the University of Saskatchewan. A gas chromatograph headspace auto sampler system was used to analyze the chemical concentrations. The effect of salinity on the equilibrium distribution of selected organic contaminants between water and air was studied. Concentrations of sodium chloride from 100 to 1000 mol/m3 were used to simulate various levels of salinity in water at a temperature of 20°C. Typical seawater was simulated with 3.5% sodium chloride and tested at temperatures from 15°C to 45°C. A modified van't Hoff expression was developed by incorporating a salting-out coefficient to predict the effect of temperature and salinity on the equilibrium distribution. The parameters of the modified van't Hoff model were determined by using the experimental results for selected organic contaminants.Key words: water pollution, volatile organic contaminants, distribution, salinity.