The impact of trade on fuel-related mercury emissions in Beijing-evidence from three-scale input-output analysis

For urban economies heavily dependent on trade, a systems analysis incorporating the effect of trade is demanded to investigate their overall energy consumption and environmental emissions. A three-scale input-output analysis which distinguishes local, domestic and international activities is presented in this study to evaluate the embodiment fluxes of fuel-related mercury emissions by China's capital city in 2010, in light of the mercury intensities for the average world and national economies. The results show that Beijing's embodied mercury emissions resulting from final fuel consumption were 7.79 t in 2010, more than 3/4 of which were attributed to domestic and international imports. These findings indicate that Beijing outsourced the majority of its fuel-related mercury emissions to regions via trade. Owing to the large-scale infrastructure construction, capital formation contributed the largest amount of embodied mercury emissions among all the final consumption types. This study suggests that multi-scale governance and comprehensive mitigation strategies are urgently needed to alleviate Beijing's mercury pollution, as the local emissions reduction depends on the overall abatement at national and international scale. The present study not only brings insights to Beijing's air pollution control but also can be used as a reference for other urban economies with heavy dependence on trade.