Measurement of Atmospheric Mercury: Current Limitations and Suggestions for Paths Forward.

Mercury (Hg) researchers have made progress in understanding atmospheric Hg, especially with respect to oxidized Hg (Hg II ) that can represent 2 to 20% of Hg in the atmosphere. Knowledge developed over the past ∼10 years has pointed to existing challenges with current methods for measuring atmospheric Hg concentrations and the chemical composition of Hg II compounds. Because of these challenges, atmospheric Hg experts met to discuss limitations of current methods and paths to overcome them considering ongoing research. Major conclusions included that current methods to measure gaseous oxidized and particulate-bound Hg have limitations, and new methods need to be developed to make these measurements more accurate. Developing analytical methods for measurement of Hg II chemistry is challenging. While the ultimate goal is the development of ultrasensitive methods for online detection of Hg II directly from ambient air, in the meantime, new surfaces are needed on which Hg II can be quantitatively collected and from which it can be reversibly desorbed to determine Hg II chemistry. Discussion and identification of current limitations, described here, provide a basis for paths forward. Since the atmosphere is the means by which Hg is globally distributed, accurately calibrated measurements are critical to understanding the Hg biogeochemical cycle.