US EPA

4964473 

Journal Article 

Tracing historical trends of Hg in the Mississippi River using Hg concentrations and Hg isotopic compositions in a lake sediment core, Lake Whittington, Mississippi, USA 

Gray, JE; Van Metre, PC; Pribil, MJ; Horowitz, AJ 

2015 

Yes 

Chemical Geology
ISSN: 0009-2541 

395 

80-87 

10.1016/j.chemgeo.2014.12.005 

WOS:000349861600007 

Concentrations and isotopic compositions of mercury (Hg) in a sediment core collected from Lake Whittington, an oxbow lake on the Lower Mississippi River, were used to evaluate historical sources of Hg in the Mississippi River basin. Sediment Hg concentrations in the Lake Whittington core have a large 10-15 y peak centered on the 1960s, with a maximum enrichment factor relative to Hg in the core of 4.8 in 1966. The Hg concentration profile indicates a different Hg source history than seen in most historical reconstructions of Hg loading. The timing of the peak is consistent with large releases of Hg from Oak Ridge National Laboratory (ORNL), primarily in the late 1950s and 1960s. Mercury was used in a lithium isotope separation process by ORNL and an estimated 128 Mg (megagrams) of Hg was discharged to a local stream that flows into the Tennessee River and, eventually, the Mississippi River. Mass balance analyses of Hg concentrations and isotopic compositions in the Lake Whittington core fit a binary mixing model with a Hg-rich upstream source contributing about 70% of the Hg to Lake Whittington at the height of the Hg peak in 1966. This upstream Hg source is isotopically similar to Hg isotope compositions of stream sediment collected downstream near ORNL. It is estimated that about one-half of the Hg released from the ORNL potentially reached the Lower Mississippi River basin in the 1960s, suggesting considerable downstream transport of Hg. It is also possible that upstream urban and industrial sources contributed some proportion of Hg to Lake Whittington in the 1960s and 1970s. Published by Elsevier B.V. 

Mercury concentrations; Mercury isotopes; Sediment core; Anthropogenic mercury