Evaluation of GOM Measurement Artifacts at the Mauna Loa AMNet Site

Winston Luke1, Paul Kelley2, Xinrong Ren3, Mark Olson4, Nash Kobayashi5, Richard Artz6 and David Schmeltz7

Recent laboratory and field research has documented and explored the biases and inaccuracies of the measurement of gaseous oxidized mercury (GOM) compounds using KCl-coated denuders. We report on the development of a simple, automated GOM calibration source and its deployment at NOAA/Air Resources Laboratory’s Atmospheric Mercury Network (AMNet) site at the Mauna Loa Observatory (MLO) on the island of Hawaii.  NOAA/ARL has developed a permeation-tube based calibration source with an extremely simple flow path that minimizes surface adsorptive effects and losses. The source was used to inject HgBr2 into one of two side-by-side Tekran® mercury speciation systems at MLO to characterize GOM measurement accuracy under a variety of atmospheric conditions. Due to its unique topography and meteorology, MLO experiences katabatic (upslope/downslope) mesoscale flow superimposed on the synoptic trade wind circulation of the tropics. Water vapor, ozone, and other trace atmospheric constituents often display pronounced diurnal variations at the site, which frequently encounters air characteristic of the middle free troposphere at night, and of the tropical marine boundary layer during the day. Results presented here will assist in the better understanding of the biases underlying GOM measurements in global mercury monitoring networks and may allow the development of correction factors for ambient data.

 

1NOAA/ARL, Winston.Luke@noaa.gov
2NOAA/ARL, Paul.Kelley@noaa.gov
3NOAA/ARL, Xinrong.Ren@noaa.gov
4NADP/ISWS, mlolson@illinois.edu
5NOAA/ESRL/GMD, Nash.Kobayashi@noaa.gov
6NOAA/ARL, Richard.Artz@noaa.gov
7EPA/CAMD, Schmeltz.David@epa.gov