Combating air pollution significantly reduced air mercury concentrations in China

Long-term observations of atmospheric mercury are important for the evaluation of the effectiveness of the Minamata Convention on Mercury. We continuously measured gaseous elemental mercury (GEM) concentrations at four remote sites in China for more than ten years, i.e., Mt. Waliguan (100.90° E, 36.29° N) during 2008-2022, Mt. Changbai (128.11° E, 42.40° N) during 2008-2022, Mt. Ailao (101.02° E, 2453° N) during 2011-2022, and Mt. Damei (121.57° E, 29.63° N) during 2011-2022. Our observations showed that GEM concentrations in China increased slightly during 2008-2013, and then the GEM concentrations decreased significantly after 2013. The mean GEM concentrations at the four Chinese sites during 2022 were 1.51 ± 0.35 ng m^-3, which is close to mean concentrations observed in Europe, North America, the Arctic, and the free troposphere in Pacific Ocean during 2021 (Individual means: 1.14 to 1.51 ng m^-3, overall mean: 1.34 ± 0.11 ng m^-3, n = 13). During 2013-2022, GEM concentrations in China decreased by 35%, which was much higher than the decreasing rates observed in Europe (9%), North America (10%), the Arctic (6%), and the free troposphere in Pacific Ocean (9%) during 2013-2021. The declines in in GEM concentrations in China since 2013 matches well with the decreasing anthropogenic Hg emission in China estimated by Chinese anthropogenic Hg emission inventory, indicating the reduction in anthropogenic Hg emissions in China was the major driver for the GEM declines.