19 November 2004
Posted in Center Information
Reinhart, Debra R., November 2004, Report #0232004-04 (3.2mb)Odor problems are a common complaint from residents living near construction and demolition (C&D) landfills. Many compounds can cause malodorous conditions. However, hydrogen sulfide (H2S) has been identified as a principal odorous component from C&D landfills. Although several studies have reported the ambient concentrations of H2S near C&D landfills, few studies have quantified emission rates of H2S. The most widely used and proven technique for measuring gas emission rates from landfills is the flux chamber method. Typically the flux chamber is a cylindrical enclosure device with a spherical top which limits the gas emission area. Pure zero grade air is introduced into the chamber, allowed mixing with emitting gases captured from the landfill surface, and then transported to the exit port where concentrations can be measured. Flux measurements using the flux chamber were performed at five different C&D landfills from June to August, 2003. The flux rates of H2S measured in this research were three to six orders of magnitude lower than the flux rates of methane reported in the literature.
In addition to the H2S flux measurements, dispersion modeling was conducted, using the EPA dispersion model, Industrial Source Complex Short Term (ISCST3), in order to evaluate impacts on landfill workers and communities around the landfills. The modeling results were analyzed to estimate the potential ground level maximum H2S concentrations for 1-hr and 3-min periods and the frequency (occurrences per year) above the H2S odor detection threshold for each landfill. Odor complaints could be expected from four among five landfills selected for this study, based on 0.5-ppb odor detection threshold.
Based on the H2S flux measurements, one C&D debris landfill was selected for field study to evaluate H2S attenuation by different cover materials. A 60ft by 40 ft area was divided into six test plots where six different cover materials were used, including sand, fine concrete, compost, agricultural lime amended sand, and two different hydraulic lime amended sand. A serial of sampling tubing were install into the cover materials to measure H2S concentrations at different depth. And the flux chamber was used to measure the H2S flux. Based on preliminary results, those cover materials do show effects on H2S generation and H2S attenuation because of their different physical and chemical characteristics. H2S generation was inhibited by high temperature in the compost test plot and alkaline cover materials in the lime amended test plots. The possible H2S attenuation mechanisms by cover material include physical adsorption, chemical reaction and biological degradation.