Laboratory measurements of the volatilization of PCBs from amended dredged material.

Since 1997, over 6 million cubic meters of material dredged from the navigation channels of NY/NJ Harbor has been amended with Portland cement and then used as fill and capping material at landfill and brownfield sites in New Jersey, New York, and Pennsylvania. Previous studies have determined that polychlorinated biphenyls (PCBs) will volatilize from this material as it dries. In the present study, time constants for the decay of the volatilization rate were determined taking into account the degree of stabilization. The experiments were conducted in a laminar flow flux chamber in which air was drawn past the dredged material and then through a polyurethane foam (PUF), sample matrix. The concentration of PCBs on the PUF found at various time increments at the downstream end of the chamber was compared to that found for the same time increments in a PUF installed in an air sampler at the upstream end of the chamber in order to calculate the flux. The time constant determined for raw dredged material was about 4 times greater than material stabilized with 8% Portland cement. The average time constants for the decay of flux rates from raw dredged material were 56, 67, and 60h for the di-, tri-, and tetra-chlorinated homologues, respectively. These times decreased with increasing proportion of Portland cement in the mixture. When stabilized with 8% Portland cement, the average time constants were 14, 13, and 19h, respectively. The effects of temperature on PCB flux rate were also investigated. The results suggest that a 3 degrees C temperature increase will more than double the flux rate.

Diffusion of acetophenone and phenethyl alcohol in the calcium-alginate-bakers' yeast-hexane system.

The intrabead diffusion coefficients of acetophenone and phenethyl alcohol were measured at 30 degrees C in the triphasic immobilized yeast-water-hexane system. Saccharomyces cerevisiae cells were deactivated with hydrochloric acid and entrapped in calcium-alginate beads. Measurements of dry cell loss during deactivation, shrinkage of the beads during deactivation and the final porosity of the beads were made for various cell loadings. Final concentrations of wet cells in the beads ranged from approximately 0.25 to 0.30 g/mL. Mass transfer in the hexane phase, external to the beads, was eliminated experimentally. The estimated error of 5% to 10% in the diffusion coefficients is within the experimental error associated with the bead method. The effect of significant sampling volumes on the diffusivities was estimated theoretically and accounted for experimentally. The intrabead concentration of acetophenone and phenethyl alcohol was 150 to 800 ppm. The deactivated cells were shown to be impervious to acetophenone so that the measured diffusivities are extracellular parameters. The cell volume fraction in the beads ranged from 0.70 to 0.90, significantly higher than previously reported data. The effective diffusion coefficients conform to the random pore model. No diffusional interaction between acetophenone and phenethyl alcohol was observed. The addition of 2 vol% ethanol or methanol slightly increased the diffusivities. The thermodynamic partition coefficients were measured in the bead-free water-organic system and found to be an order of magnitude lower than the values calculated from the analysis of the diffusion data for the organic-bead system, suggesting that bead-free equilibrium data cannot be used in triphasic systems. (c) 1994 John Wiley & Sons, Inc.