GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 38-8
Presentation Time: 4:05 PM


VAREKAMP, Johan C., Dept. of Earth & Environmental Sciences, Wesleyan University, 265 Church Street, Middletown, CT 06459,

Environmental geochemists analyze ambient media and identify contaminant sources from a range of evidence, including spatial association. Haynes (2012) studied Hg in air and lake sediment in Costa Rica, following up on published data of high ambient Hg in local air. She found no evidence for a high natural volcanic Hg background in Costa Rica. She analyzed hair from local citizens, with documentation of their diet. This Costa Rican sample (53 people) had a higher % individuals with Hg-in-hair above EPA recommended limits than in the USA. Some of those with higher Hg-in-hair consumed abundant marine fish, so we concluded that potential Hg issues in Costa Rica may be closer related to diet than to proximity to actively degassing volcanoes. Subsequent studies in Costa Rica found similar correlations between diet and Hg-in-hair. A local fishermen trade union learned through press coverage of our study and wanted a formal retraction of these results, criticizing the statistics applied. In our public statements we stressed that the data only applied to our sample population, but the results suggested that a broader study would be worthwhile. Mercury bio-magnifies in marine ecosystems, with the highest Hg levels in large fish (swordfish, tuna). Many of these fish are cosmopolitan, and some fish in Costa Rica is imported, so most large marine fish consumed in Costa Rica presumably have high Hg. We have not retracted the results of our study and stand behind the interpretation.

In a study of sediment from coves of the Connecticut River, relatively high Hg concentrations are found south of Hartford (CT), whereas much lower Hg levels occur further north (Woodruff et al. 2013). Very high Hg levels were found in Wethersfield Cove, an oxbow pond just south of Hartford, close to a former GE-designed power plant that used Hg instead of steam as the working fluid. It pumped thousands of lbs of Hg/hour through the turbines, and lost large amounts of Hg over its 30 years of power production. We estimated the mass of lost Hg from documents stored at the Smithsonian Institution in DC. We have not yet firmly concluded that the Hg enrichments in coves of the lower Connecticut River derive from Hg spills at this power plant. The question is: when is evidence strong enough to pinpoint a potential contaminant source without making ourselves liable to legal repercussions?