Decline in mercury emissions in recent decades: positive signs of pollution reduction despite global estimates

Mercury emissions caused by human activity: new findings

The latest scientific research reveals encouraging conclusions about the reduction of mercury emissions, one of the most dangerous pollutants, which enters the atmosphere as a byproduct of human activities. Analyses have shown that during the period from 2005 to 2020, the concentration of mercury in the atmosphere decreased by approximately 10%, contrary to what global emissions inventories indicated through their estimates. These discoveries are based on data collected from 51 monitoring stations for atmospheric mercury in the northern hemisphere, and researchers employed advanced modeling methods to better understand what caused this positive trend.

Although global inventories estimate pollution emissions based on average emission rates that include activities like coal burning or gold mining, these models often fail to account for actual measurements coming from the field. This highlights the need for constant monitoring of real data to improve prediction models and policies for future emissions. Such results have important implications for scientists and policymakers seeking better insights into global pollution trends and the health of our planet.

What did the monitoring results show?

Studies have shown that the reduction in atmospheric mercury concentration is likely linked to lower emissions from human sources, including reduced mercury use in industrial processes, progress in pollution control, and a shift to cleaner energy sources. For example, a significant reduction in mercury use in small-scale gold mining represents an important step towards decreasing global emissions. Gold mining, especially in underdeveloped areas, uses mercury to extract gold from soil, contributing a large percentage of total mercury emissions into the atmosphere.

Although the Minamata Convention, an international treaty signed in 2013 aimed at reducing mercury emissions, was a key step forward, actual data indicates that emissions are declining even faster than some global inventories had assumed. However, challenges remain in accurately modeling mercury emissions due to the specific properties of this metal. Mercury is the only metal that is liquid at room temperature, which means it easily enters the atmosphere and can be re-emitted from natural "reservoirs" such as oceans and soil. These factors make precise estimation of mercury emissions more complex.

Research methods and modeling challenges

Scientists in this study utilized two main modeling methods for emissions: biogeochemical box modeling and chemical transport modeling. Both methods allowed researchers to conduct thousands of simulations to assess various emission scenarios and better understand the impact of meteorological and regional variations on mercury concentration in the atmosphere. Although the results of these models suggested several possible factors, the reduction of emissions from human sources was the most likely reason for the recorded decline in atmospheric mercury.

However, global inventories still show discrepancies in emissions estimates. One reason for this discrepancy may be the lack of data from certain countries, especially those where gold mining occurs in remote and poorly accessible areas. Additionally, monitoring stations for atmospheric mercury are less developed compared to those for other pollutants like methane, complicating accurate tracking of global emissions trends.

The need for long-term monitoring

The results of this study emphasize the importance of long-term monitoring of emissions and the establishment of more monitoring stations for mercury worldwide. Scientists also note that further research is necessary for better estimation of emissions from products containing mercury, such as thermometers or other equipment. These products, when discarded, can release mercury into the atmosphere over long periods, further complicating emissions tracking.

In the future, international collaboration among scientists is expected to enable better estimation of emissions and help achieve global goals for reducing mercury pollution. Given the results so far, optimism is growing that emissions will continue to decrease, but more work is needed to ensure ongoing reductions in mercury emissions and better protection of human health and the environment.

Source: Massachusetts Institute of Technology