Quantifying the effects of China’s pollution control on atmospheric mercury emissions

Thursday, 18 December 2014
Hui Zhong, Nanjing University, Nanjing, China
China has conducted series of air pollution control policies to reduce the pollutant emissions. Although not specifically for mercury (Hg), those policies are believed to have co-benefits on atmospheric Hg emission control. On the basis of field-tests data and updated information of energy conservation and emission control, we have developed multiple-year inventories of anthropogenic mercury emissions in China from 2005 to 2012. Three scenarios (scenario 0(S0), scenario 1(S1), scenario 2(S2)) with different emission controls and energy path are designed for prediction of the future Hg emissions for the country. In particular, comprehensive assessments has been conducted to evaluate the evolution of emission factors, recent emission trends, effects of control measures as well as the reliability of our results. The national total emissions of anthropogenic Hg are estimated to increase from 679.0 metric tons (t) in 2005 to 749.8 t in 2012, with the peak at 770.6 t in 2011. The annual growth rate of emissions can then be calculated at 2.1% during 2005-2011, much lower than that of energy consumption or economy of the country. Coal combustion, gold metallurgy and nonferrous metal smelting are the most significant Hg sources of anthropogenic origin, accounting together for 85% of national total emissions. Tightened air pollution controls in China should be important reasons for the smooth emission trends. Compared with 2005, 299 t Hg were reduced in 2010 from power plants, iron and steel smelting, nonferrous-smelting and cement production, benefiting from the improvement of control measures for those sectors. The speciation of Hg emissions is relatively stable for recent years, with the mass fractions of around 55%, 9% and 6% for Hg0, Hg2+ and Hgp respectively. Integrating the policy commitments on energy saving, different from the most conservative case S0, S2 shares the same energy path with S1, but includes more stringent emission control. Under those scenarios, we predict China’s atmospheric Hg emissions are 814, 805, and 620 t for 2015, 844, 823, and 621t for 2020, and 869, 813t, and 579t for 2030. Compared to levels of energy consumption and industrial production, policies on emission control would have greater benefits for Hg abatement for the country.