Atmospheric mercury (Hg) has been measured for decades around the world. Air monitoring has evolved over time from manual weekly traps to sophisticated instruments sampling on very short intervals. The next wave of Hg sampling has been developed using passive air sampling for even longer measurement time periods. Overall, it is the end goal of the monitoring that dictates what sampling method should be employed. Should  processes research in an aircraft be the study, then the automated instrument is selected; should a regional network to investigate trends be the goal, then weekly traps is selected. With the goal of long term trend monitoring and filling in large regional gaps such as that of the Minamata Convention on Mercury (MCM),  the passive sampling method is a good tool to select.

In collaboration with Environment and Climate Change Canada (ECCC), the University of Toronto Scarborough developed a passive air sampler for gaseous Hg. This sampling system has been fully characterized and is now in commercial production by Tekran Inc. and sold under the MerPAS name. The MerPAS passive air sampler uses sulfur-impregnated activated carbon as the sorbent for Hg which undergoes diffusive uptake and accumulation on the sorbent. This method has been shown to have accuracy on par with currently acceptable methodologies for measuring Hg in the atmosphere and demonstrates excellent precision. However, this is not the only passive sampling method being used around the world. In addition to the MerPAS, the Italian Institute of Atmospheric Pollution Research (CNR-IIA) and the Swedish Environmental Research Institute (IVL) have also developed passive sampling devices for Hg. Thus, in the winter of 2019, a field based intercomparison and a controlled blind performance comparison amoung 3 different devices was undertaken. Preliminary results from this intercomparison will be presented.

As presented at last fall’s NADP meeting, ECCC has initiated a pilot study to investigate the application of passive sampling of atmospheric Hg on a global scale by developing a global network made up of currently existing networks (a “network of networks”) in combination with the expansion of some of those networks to reduce areas with no coverage. NADP is now a partner in this pilot global network with 5 sites in the US at Beltsville, Sequoia and Kings Canyon, Mingo National Wildlife Refuge, Toolik and Marcell. We now have 29 countries and almost 50 sites currently collecting data with more to come. Updates on this project will be presented in addition to the challenges experienced in undertaking this kind of new network monitoring.