Global mercury emissions declined by 30 per cent between 1990 and 2010, recent research has shown.
In a joint project between US-based Harvard University, China’s Peking University, the US Geological Survey, Germany’s Max Planck Institute for Chemistry and Canada’s University of Alberta, scientists found that measures taken by the energy sector have contributed significantly to the downward trend.
Among the measures mentioned were clean coal technology, switching from coal-fired to gas-fired generation, and the implementation of more stringent NOx and SOx emissions control standards, which also reduced mercury emissions.
The researchers said they observed the “most pronounced” reduction in mercury in the atmosphere over North America and Europe, where the strongest controls have been implemented.
Contrary to accepted theories of mercury emission, which focus on a worldwide emissions index, the study found that local and regional mitigation efforts have had more impact on global emissions than previously thought. While mercury emissions from Asia grew between 1990 and 2010, the study found that reductions in Europe and North America “more than offset” these increases.
“For years, mercury researchers have been unable to explain the apparent conundrum between declining air concentrations and rising emission estimates,” said Harvard University’s Yanxu Zhang, the study’s lead author. “Our work is the first detailed, mechanistic analysis to explain the declining atmospheric mercury trend.”