L. J. Thibodeaux

Models of mechanisms for the vapor phase emission of hazardous chemicals from landfills

Abstract Quantities of hazardous chemicals have been placed in sanitary landfills in conjunction with solid waste. This paper presents three vapor phase transport mechanisms: molecular diffusion, bio-gas convection, and barometric pressure pumping. These mechanisms are incorporated into a dynamic model that simulates the emission flux rate of chemicals, as a function of landfill and environmental variables. The simulation model is driven by time-varying atmospheric pressure fluctuations. Darcys law is used to simulate gas movement through the landfill cap material to and from the landfill cells. With all mechanisms operative, a rate of 290 g benzene/m 2 d was obtained from the model using benzene as a test chemical. Atmospheric pressure fluctuations pump toxic vapors and gases from the storage cells of hazardous waste landfills to the air above. This pumping enhances the vapor phase molecular diffusion process. The calculated benzene flux rate with diffusion and atmosphere pumping was 13 g/m 2 d. Uncertainties and limitations of the model are considered which include: vapor and gas circulation in and between cells, adsorption onto solids and multi-cell landfills. The model presented is a practical tool for initial evaluation studies of volatile chemical emissions from landfills and provides a basis upon which to construct more realistic simulation models.

In Situ Methods to Control Emissions from Surface Impoundments and Landfills

This report presents the results of a two-year study which included laboratory investigations as well as a comprehensive literature review on methods of reducing the rate of emissions of volatile chemicals from surface impoundments and landfills. It presents information on the following in-situ methods which may be employed to reduce emission rates: air supported structures, floating solid objects, shape modification, aerodynamic modification, floating oil and/or surfactant covers and synthetic membranes over landfills. Conclusions are drawn with respect to the suitability of each of the methods under various circumstances and the degree of control which might be expected. The full report was submitted in fulfillment of Cooperative Agreement No. 810856-01-1 by the University of Arkansas under the sponsorship of the U.S. Environmental Protection Agency. This report covers a period from October 1, 1983 to September 30, 1985. The full report is under CR710856. This project summary was developed by EPA’s Haza...