Manganese Can Contribute to Mercury Emission from Soils

The Science

Mercury is found in the environment due to release from natural and manmade sources. As such, mercury is a common pollutant in soils and sediments and a major environmental concern due to its toxicity to humans and wildlife. Researchers found manganese can transform mercury(II) to volatile mercury(0).

The Impact

The release of volatile mercury from soils and sediments is a critical process in the global movement of mercury; however, the transformation of mercury(II) to mercury(0) is not well understood. Researchers know bacteria and other microorganisms can transform mercury(II) to mercury(0) under oxygen-limited conditions, as can iron-bearing minerals. However, this study shows manganese, which is commonly found in water-logged soils and oxygen-deficient freshwater and marine sediments, can also cause this transformation under mildly oxic conditions. This insight will help improve models of mercury global transport, thereby advancing efforts to protect human health and the environment.

Summary

Mercury is found in the environment due to release from volcanoes, mining activity, the burning of forests and fossil fuels, and industrial and consumer use. As such, mercury is a common contaminant in many terrestrial and aquatic environments, and its bioaccumulation in organisms, including humans, is a major environmental concern. Mercury in the environment is present as either mercury(II), which tends to remain in soils and sediments, or mercury(0), which as a gas can escape into the atmosphere and is mobile on a global scale. Thus, the reduction of mercury(II) to mercury(0) in soils and sediments, by either bacteria and other microorganisms or by chemical reactions, is a key component of mercury cycling between atmospheric and aquatic/terrestrial reservoirs and the overall biogeochemical cycling of mercury.

Researchers used X-ray spectroscopic capabilities at the Advanced Photon Source at Argonne National Laboratory to show that manganese(II), which is found in oxygen-deficient soils and sediments, can reduce mercury(II) to mercury(0) and partially reduce mercury(II) to mercury(I) in the presence of high sulfate or chloride, a previously unknown process in mercury’s biogeochemistry. The finding that manganese(II) may play a role in the emission of mercury(0) from soils and sediments at the oxic-anoxic interface can lead to improved models of global mercury cycling and better protection of human health and the environment.

Principal Investigator

Kemner Kenneth
Argonne National Laboratory
[email protected]

Co-Principal Investigator

Edward O'Loughlin
Argonne National Laboratory
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This work was supported by the U.S. Department of Energy (DOE) Office of Science, Biological and Environmental Research program, Environmental System Science program via the Wetland Hydro-biogeochemistry Science Focus Area at Argonne National Laboratory. MRCAT/EnviroCAT operations were supported by DOE and the MRCAT/EnviroCAT member institutions. This research used resources of the Advanced Photon Source, a DOE Office of Science User Facility operated by Argonne National Laboratory.

References