147 - Permeation Tube-Based Calibration of Atmospheric Oxidized Mercury Measurements

Most measurements of atmospheric oxidized mercury (HgII) to date have been uncalibrated. With discrepancies surrounding systems used to measure HgII, and uncertainties surrounding atmospheric mercury (Hg) redox chemistry, it is crucial that calibration efforts are made in order to confirm the accuracy of HgII measurement systems, and to gain a better understanding of Hg cycling in the atmosphere. We have developed a permeation tube-based automated calibration system capable of calibrating for HgII in ambient conditions. The mass loss of the permeation tubes is determined gravimetrically and via gas chromatography-mass spectrometry (GC/MS). Using GC/MS we are able to quantitatively assess Hg compounds emitted from the permeation tubes and the calibrator. Laboratory tests have shown that differences in carrier gas (e.g. helium vs nitrogen) and orientation of a critical flow orifice (e.g. upstream or downstream of the permeation tube) affect the permeation rate and composition (percent HgII) of the emitted compounds. A previous iteration of the calibrator was successfully deployed at the Mauna Loa Observatory in Hawaii and Nevada, USA. Since the aforementioned deployments, we have made several improvements to the calibrator and methods for characterization of the permeation tubes. The current iteration of the calibrator was deployed, and in operation alongside USU’s dual-channel system at Storm Peak Laboratory (~3220 m A.S.L) in Steamboat Springs Colorado, USA, from July 2021 to October 2021. Shorter injection times (

authors: Tyler Elgiar, Seth Lyman, Trevor O'Neil, Lynne Gratz, A. Gannet Hallar