Consensus Report

Investigative Strategies for Lead-Source Attribution at Superfund Sites Associated with Mining Activities (2017)

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The Superfund program of the US Environmental Protection Agency (EPA) was created in the 1980s to address human-health and environmental risks posed by abandoned or uncontrolled hazardous-waste sites. As part of this process, EPA attempts to identify parties that are responsible for the contamination and thus financially responsible for remediation. However, identifying potentially responsible parties is complicated because Superfund sites can have a long history of use and involve contamination that can have many sources. Such is the case of mining sites that involve lead contamination. At the request of Congress, this report examines the extent to which various sources contribute to environmental lead contamination at Superfund sites and focuses on the Southeast Missouri Lead Mining District.

The report provides investigative strategies that could be used for lead-source attribution. The strategies rely on fingerprinting approaches in which unique physical or chemical properties of lead or lead-associated materials are used to distinguish sources from one another. A promising approach highlighted in the strategies is lead isotopic analysis. Ore deposits and other geologic materials can have a wide array of lead-isotopic ratios that can be used to distinguish them from each other and products derived from them. The report's authoring committee demonstrates how lead-isotope ratios can be used to distinguish commercial lead sources, such as paint and gasoline, from Southeast Missouri ores and mining wastes. Other techniques -- such as ones that rely on analysis of mineralogy, particle size, chemical speciation, and other source-associated elemental ratios or isotopes -- are also discussed that could help attribute potential sources if lead isotopic analysis is not definitive.

The report recommends further research that will provide opportunities to enhance the analytic techniques and methods that make up the committee's proposed investigative strategies and to reduce uncertainty in their implementation.