Design of laboratory systems for controlling the activity of moderately volatile organic compounds

The gas-phase transfer of hexachlorobenzene (HCB) from the solid to the chambers used for sediment-water bioaccumulation tests was investigated. The physical properties of HCB found in the literature are summarized. Significant discrepencies were found among different methods. The chief sources in uncertainty in these data were due to variations in temperature, and the possible incomplete equilibration of the solid with the gas. These items are discussed in detail. The theory for transfer from gas to a liquid is developed. The effects of association of HCB with humate and other competing processes (head space losses, adsorption to food, organisms, sediment) are included. Experimental data from the use of the apparatus in actual bioaccumulation experiments are discussed.