354 - Updated Trends for Atmospheric Mercury in the Arctic: 1995-2018

Understanding the transport, deposition and variability of atmospheric mercury (Hg) to the Arctic is important for protecting human and wildlife exposure to mercury. Continuous Hg measurements, spanning 20 years, and increased monitoring sites has allowed a more comprehensive understanding of how Arctic mercury trends are changing over time. Time-series trend analysis of TGM (Total gaseous mercury) in air was performed for 10 long-term Hg air monitoring stations, comprising of High Arctic, coastal arctic and subarctic locations. GOM (Gaseous oxidised mercury) and PHg (particulate bound mercury) measurements were also available at two high arctic sites. Seasonal TGM concentrations at coastal High Arctic sites showed the greatest variability, with daily mean maximums ranging between 4.21 ng m-3 and 2.41 ng m-3, largely driven by local chemistry. TGM concentrations for the sub-Arctic sites were lowest during fall ranging from 1.13 ng m-3 to 1.30 ng m-3. Annual mean TGM trends were negative for 8 of the 11 sites. High-Arctic TGM trends ranged from -0.8% to -2.6% yr-1 during fall, reflecting a decrease in background concentrations. The sub-Arctic sites also showed a negative trend during winter, with only Little Fox Lake (western Canada) having a positive trend (1.4% yr-1). High-arctic speciation of GOM and PHg at Alert and Zeppelin showed opposing trends with Alert moving towards increasing GOM and Zeppelin moving towards increasing PHg. These results suggest changes to the processes that affect the transformation, deposition and input of mercury to the Arctic. These overall changes in Hg trends across the Arctic are attributed to reductions in anthropogenic emissions and changes in meteorological conditions.

Authors: Katrina Macsween, Geoff Stupple, Alexandra Steffen, Katriina Kyllönen, Katrine Aspmo Pfaffhuber, Henrik Skov, Wenche Aas, Michelle Nerentorp Mastromonaco, Torunn Berg