Mercury-impacted scrap metal: Source and nature of the mercury

• Published in: Journal of environmental management Vol. 161; pp. 303 - 308
• Main Authors: Finster, Molly E., Raymond, Michelle R., Scofield, Marcienne A., Smith, Karen P.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.09.2015; Academic Press Ltd; Elsevier
• Subjects: Emissions; Environmental management; Environmental Pollutants - analysis; Human exposure; Humans; Industrial Waste - analysis; Mercury; Mercury - analysis; Mercury switches; Mercury-impacted metal; Metal recycling; Metallurgy; Metals - analysis; Metals - chemistry; Occupational health; Oil and gas scrap; Recycling; Scrap; Scrap metal; Steel; United States; United States; Mercury switches; Mercury-impacted metal; Scrap metal; Mercury; Oil and gas scrap; Metal recycling
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2015.05.041

The reuse and recycling of industrial solid wastes such as scrap metal is supported and encouraged both internationally and domestically, especially when such wastes can be used as substitutes for raw material. However, scrap metal processing facilities, such as mini-mills, have been identified as a source of mercury (Hg) emissions in the United States. This research aims to better define some of the key issues related to the source and nature of mercury in the scrap metal waste stream. Overall, it is difficult to pinpoint the key mercury sources feeding into scrap metal recycling facilities, quantify their associated mercury concentrations, or determine which chemical forms are most significant. Potential sources of mercury in scrap metal include mercury switches from discarded vehicles, electronic-based scrap from household appliances and related industrial systems, and Hg-impacted scrap metal from the oil and gas industry. The form of mercury associated with scrap metal varies and depends on the source type. The specific amount of mercury that can be adsorbed and retained by steel appears to be a function of both metallurgical and environmental factors. In general, the longer the steel is in contact with a fluid or condensate that contains measurable concentrations of elemental mercury, the greater the potential for mercury accumulation in that steel. Most mercury compounds are thermally unstable at elevated temperatures (i.e., above 350 °C). As such, the mercury associated with impacted scrap is expected to be volatilized out of the metal when it is heated during processing (e.g., shredding or torch cutting) or melted in a furnace. This release of fugitive gas (Hg vapor) and particulates, as well as Hg-impacted bag-house dust and control filters, could potentially pose an occupational exposure risk to workers at a scrap metal processing facility. Thus, identifying and characterizing the key sources of Hg-impacted scrap, and understanding the nature and extent of associated releases, represent a practical research need that is essential for improving the environmental management of Hg-impacted scrap and assessing measures to protect workers from potential health and safety hazards that might be posed by mercury and Hg-impacted scrap. •Metal surfaces have the potential to accumulate Hg in considerable quantities.•Hg exists predominantly in the elemental form in the surface corrosion layer.•Sources of Hg in scrap include Hg-switches, electronic devices, and industry scrap.•Recycling of Hg-impacted scrap could result in gas and particulate emissions.•Hg-impacted scrap may pose occupational exposure risks for metal recycling workers.