Do We Understand What
the Mercury Speciation Instruments
Are Actually Measuring? Results of RAMIX
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Abstract
From August 22 to September 16, 2012, atmospheric mercury
(Hg)
was measured from a common manifold in the field during the Reno Atmospheric
Mercury Intercomparison eXperiment. Data were collected using Tekran
systems, laser induced fluorescence, and evolving new methods. The
latter included the University of Washington-Detector for Oxidized
Mercury, the University of Houston Mercury instrument, and a filter-based
system under development by the University of Nevada-Reno. Good transmission
of total Hg was found for the manifold. However, despite application
of standard protocols and rigorous quality control, systematic differences
in operationally defined forms of Hg were measured by the sampling
systems. Concentrations of reactive Hg (RM) measured with new methods
were at times 2-to-3-fold higher than that measured by Tekran system.
The low RM recovery by the latter can be attributed to lack of collection
as the system is currently configured. Concentrations measured by
all instruments were influenced by their sampling location in-the-manifold
and the instrument analytical configuration. On the basis of collective
assessment of the data, we hypothesize that reactions forming RM were
occurring in the manifold. Results provide a new framework for improved
understanding of the atmospheric chemistry of Hg