image: On the left can be seen a much larger decline in GEM concentrations in China than elsewhere in the Northern Hemisphere. On the right is the trends in criteria pollutant concentrations in China. These trends suggest the co-benefits of emission control measures contributed to the reduced anthropogenic mercury emissions and led to the GEM decline in China. Figure by Xinbin Feng.
Credit: Figure by Xinbin Feng.
This study is led by Dr. Xinbin Feng (Institute of Geochemistry, Chinese Academy of Sciences) and Dr. Xuewu Fu (Institute of Geochemistry, Chinese Academy of Sciences). Over a decade of continuous observations of atmospheric gaseous elemental mercury (GEM) were conducted at four remote sites in China. The observations in China showed the highest mean GEM concentration of 2.49 ng m-3 in 2013, 70% higher than the mean at other global network sites. Mean GEM decreased continuously to 1.48 ng m-3 in 2022, which is broadly similar to background mean in the Northern Hemisphere. From 2013 to 2022, GEM concentrations in China decreased by 38.6 ± 12.7%, which is approximately fourfold higher than those observed elsewhere in the Northern Hemisphere (5.7-14.2%) (see below, left image).
Xinbin Feng and Xuewu Fu, together with the co-authors from China, Canada, and USA, explore the drivers for GEM decline. The team performed a GEM source identification and investigated the relationships between the GEM trends and the trends in anthropogenic emissions, criteria air pollutants, Northern Hemispheric background, vegetation process, natural emissions, and atmospheric mercury chemistry.
The team found dominant effects of domestic anthropogenic emissions on the variations of GEM concentrations in China, and significant correlations in the trends between GEM concentrations and criteria air pollutants in China (see below, right image). “These geochemical evidences indicate that the decline in Chinese GEM concentrations is primarily driven by the reduction of domestic anthropogenic mercury emissions, likely related to the comprehensive implementation of air pollution control devices combating air pollutions,” Xinbin Feng says.
The researchers also used a machine learning model and an empirical relationship model to estimate the trends in China’s anthropogenic GEM emissions. The results show 38% and 50% declines, respectively, in anthropogenic GEM emissions in China from 2013 to 2022 (see below, left image), with most of reductions in northern, eastern, and southwestern China (see below, right image).
“The significant declines in China’s air mercury concentrations strongly support that China’s Clean Air Action have effectively reduced the domestic anthropogenic mercury emissions. This has implications for making efficient mercury pollution control tragedy under the Minamata Convention on Mercury. The response of air mercury concentrations to the changing anthropogenic emissions is faster than previous recognized, and we hope that this study will stimulate scientists to incorporate long-term continuous observations worldwide in global mercury modeling to understand the cycling of atmospheric mercury at the global scale.” Xinbin Feng says.
The quick response of air mercury concentrations to the abatement of anthropogenic emissions has not been recognized by the scientific community. Previous global atmospheric mercury budget models assumed a dominant control of natural surface mercury emissions on atmospheric mercury, and an abatement of anthropogenic emissions may not lead to large declines in air mercury concentrations. The new findings in this study highlight a more important role of anthropogenic emissions in atmospheric mercury budget, and natural surface mercury emissions are likely overestimated.
See the article:
Combating air pollution significantly reduced air mercury concentrations in China
https://doi.org/10.1093/nsr/nwae264
Journal
National Science Review