Section Three
LANDFILLS-C. GASES
27    A METHODOLOGY FOR ASSESSING
THE SORPTION PHENOMENA OF TRACE ORGANIC
COMPOUNDS FOUND IN LANDFILL GAS
Linda Stiegler, Research Assistant
Michael Stallard, Research Engineer
Robert Lang, Research Engineer
George Tchobanoglous, Professor
Department of Civil Engineering
University of California, Davis
Davis, California 95616
INTRODUCTION
The sorptive characteristics between trace organic compounds found in landfill gas and the materials in landfills are important in the study of the movement of these compounds through landfills.
Trace organic compounds that are not completely sorbed to waste or soil particles and subsequently
concerted either biotically or abiotically, can later become available for transport by gas or water that
moves through the landfill. Once these chemicals become entrained in a moving fluid, they have the
potential to escape from the landfill and contaminate the air or groundwater.
The overall goal of this study is to quantify the sorptive characteristics of solid waste and landfill
cover materials. Because field measurements are difficult to carry out under controlled conditions, an
experimental methodology using 14C labeled compounds was developed to examine sorption phenomena between selected trace organic compounds found in landfill gas and materials found in municipal
landfills. The method can be used to measure sorptive behavior at trace constituent concentrations as
low as 2 to 5 parts per billion by volume (ppbV). Trichloroethylene (TCE) and benzene are the two
trace organic compounds selected for use in this study. Trichloroethylene, a volatile organic solvent
that is sparingly water soluble, is representative of one main class of organic chemicals, chlorinated
aliphatic hydrocarbons. Benzene, also a volatile organic solvent, is representative of aromatic
hydrocarbons.
BACKGROUND
A number of trace organic compounds have been identified in landfill gas and in the atmosphere
near landfills.1 Trace organic compounds, present in landfill gas at concentrations on the order of
several parts per billion to a few parts per million by volume, are emitted from landfills as a result of
volatilization of liquid compounds present in the landfill or as a result of biological and abiotic
conversion reactions of landfilled materials. If the emission of trace organic compounds from municipal landfills to the atmosphere is to be predicted, the sorptive behavior of trace organic compounds
must be understood. Sorption of the trace organic compounds found in landfill gas onto materials
found in landfills must be quantified if the movement of these compounds through landfills and their
subsequent trace vapor emission is to be understood.
When considering sorption phenomena the following factors must be considered: 1) what characteristics of the trace constituent, e.g. saturation concentration, influence its tendency to sorb to solid
waste and various landfill cover materials, 2) what characteristics of the medium such as moisture or
carbon content2-3'4.5 most influence trace constituent sorption characteristics and 3) what environmental factors affect the process, (e.g. pH, temperature, etc.)
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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