|Abstract Title:||Atmospheric mercury variability at a terrestrial background site, South-Eastern Australia.|
|Presenter Name:||Katrina Macsween|
|Company/Institution:||Environment and Climate Change Canada|
|Session:||Special Session - Mercury in the Southern Hemisphere|
|Co-Authors:||Katrina Macsween,Dean Howard,Grant Edwards|
Abstract Information :
Understanding of Southern Hemisphere atmospheric mercury (Hg) is vastly underrepresented in the current global understanding of seasonal variation and drivers of Hg, particularly over terrestrial environments. Relationships have been observed between atmospheric Hg and air temperature, solar radiation, relative humidity, wind speed and direction and meso and macro scale atmospheric circulation, but these drivers are largely unexplored in the Southern Hemisphere. This study provides 14 months of atmospheric Gaseous Elemental Mercury (GEM) and Reactive Mercury (RM) measurements undertaken at an Australian terrestrial background site to determine seasonal variation and its potential drivers. GEM concentrations were quantified using a Tekran 2537B. Measurements of RM were undertaken concurrently using the University of Nevada-Reno Reactive Mercury Active System. Study average GEM concentrations were 0.68 ng m-3 (standard deviation ñ0.22 ng m-3). Highest concentrations occurred during austral summer and lowest in austral winter (0.88 and 0.43 ng m-3, respectively). RM 2-weekly concentrations over the study average 2.41 pg m-3 (standard deviation 1.68 pg m-3). These concentrations also peaked in summer (3.43 pg m-3) and were lowest in winter (1.93 pg m-3). Summer and spring are influenced by air masses transporting higher Hg concentrations from the north-east, over and through the Sydney urban region. Gaseous oxidation was also found to be more efficient during this time. Winter concentrations were primarily driven by ocean evasion being transported inland. Overall, atmospheric mercury trends at this site appear to be driven by seasonal shifts in the prevailing air mass transport, creating seasonal variation in the observed Hg concentrations.