Comparison of Calibration Approaches for Mercury in Emissions and Ambient Air

Mercury (Hg) emissions into the atmosphere have significant environmental and health impacts, making accurate measurement and calibration of Hg crucial for effective monitoring and mitigation strategies. Measuring the different forms of atmospheric mercury, such as gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM), and their behavior in both emissions and ambient air is essential for developing comprehensive approaches to control mercury pollution. Currently, common calibrations for GOM in emissions rely on liquid evaporative calibrators, such as HovaCal and Optoseven. However, new calibration methods are emerging to address the limitations of existing approaches. The challenges associated with GOM calibration become even more pronounced at ambient GOM concentrations, where accurate calibration is essential for reliable measurements. In our work, we validated and compared multiple GEM and GOM calibration sources over several years. We also developed a novel nonthermal plasma source that can be used for GOM calibration at both ambient and emission concentrations of Hg. Our research highlights the importance of precise calibration techniques to enhance the comparability of Hg measurement results across different studies and regions. By improving calibration accuracy, we can better evaluate the effectiveness of the Minamata Convention and other efforts aimed at reducing mercury emissions globally.