Water Quality Seminar Series

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Water Quality Seminar Series Jointly sponsored
by Institute of Natural Resource Sustainability
(INRS) and Dept. of Natural Resources and
Environmental Sciences (NRES) March 31,
2009 Noon 1 PM Illinois Natural Resources
Building (Illinois State Geological Survey) Room
101 (SE corner) 615 E. Peabody (Coffee and
cookies will be provided) Total Dissolved
Methylmercury in Freshwaters? Intercomparison of
a Novel Analytical Method with Distillation/Ethyla
tion in Samples from Freshwater Systems
by Robert J.M. Hudson Department of Natural
Resources and Environmental Sciences University
of Illinois A novel method for analyzing
methylmercury (MeHg) in filtered water samples
has been developed at the University of Illinois
and tested in geochemical studies conducted in
the Grand Calumet, the Piasa Creek watershed, and
other locations. The method combines a new
analytical system Hg-thiourea complex ion
chromatography with a novel method of sample
preparation thiourea-catalyzed SPE. It has
proved to be viable for large scale large scale
field studies and to yield geochemically
meaningful results. In conjunction with these
field studies, an intercomparison of dissolved
MeHg measurements made using the new method and a
sophisticated variant of the accepted standard
method was conducted on selected split samples.
The distillation/ethylation results, which were
obtained at Trent University using speciated
isotope dilution, were systematically lower in a
significant fraction of samples. We hypothesize
that these differences are due to the occurrence
of a highly-stable complex between MeHg and
reduced sulfur compounds in natural waters that
is not always detected when using
distillation/ethylation.