Potential Exposures to Radionuclides Originating from Technologically Enhanced Naturally Occurring Radioactive Materials Emitted by Landfill Gas Extraction and Control Systems, 20-9422Printer Friendly Version
Inclusive Dates: 09/25/03 - Current
Background - This research addressed the human health risks and environmental management issues related to disposal of technologically enhanced naturally occurring radioactive materials (TENORM) in municipal solid waste (MSW) landfills. TENORM is generated by a number of human activities including oil and natural gas production, drinking water treatment processes, and wastewater treatment plants. The economics of TENORM disposal provide an incentive to allow its disposal in nonhazardous waste landfills that also receive municipal solid waste as opposed to special waste facilities. Published assessments of the human health risks associated with disposal of TENORM in municipal solid waste landfills have failed to consider passive and active emissions of landfill-generated gases. Neglecting the effects of landfill gas generation on radon emissions could represent a serious flaw in these risk and exposure assessments.
Approach - The project evaluated the geochemical characteristics of TENORM derived from oil and gas production. This information was used to define the physical state of the waste material that would be placed in a landfill. Next, the physical and chemical processes affecting the fate and transport of radon originating from the TENORM were represented in a numerical model capable of simulating internal landfill gas pressures and flow rates due to landfill gas generation, and the resulting transport of radon caused by molecular diffusion and advective transport in the landfill gas.
Accomplishments - The numerical model was used to simulate radon emissions and atmospheric radon concentrations on and downwind from the landfill for a variety of TENORM disposal, landfill cover construction, and landfill gas control scenarios. Two TENORM disposal scenarios were considered: disposal in a discrete layer and commingling of the TENORM throughout the refuse. Although other disposal scenarios are possible, these two were considered to be likely bounding conditions in terms of radon emissions. Two cover construction scenarios were considered: a so-called "RCRA" cover consisting of (from top to bottom) a vegetative soil layer, a gravel drainage layer, and a compacted clay layer, and an alternative cover consisting only of soil. The results indicated that landfill gas generation could result in atmospheric radon concentrations exceeding ambient levels both on the landfill and several hundred meters downwind from the landfill. The lifetime excess cancer risks for off-site residents resulting from the radon emissions could approach 10-3 for a 30-year exposure.