Air Pollutant Emissions Induced by Population Migration in China.

Large-scale population migration accompanied by rapid urbanization is expected to cause the spatial relocation of air pollution because of heterogeneous energy use and consumption preferences of rural versus urban areas in China. In this study, we adopted an integrated approach by combining a population migration model and environmentally extended input-output analysis to quantify impacts of rural-to-urban (RU) and urban-to-urban (UU) migrations on emissions of NOx, SO2, and primary PM2.5 in China. Results indicate that population migration increases NOx (1.42 Mt), SO2 (1.30 Mt), and primary PM2.5 (0.05 Mt) emissions, accounting respectively for 5.4, 4.8, and 0.4% of China's total in 2012. RU migration, involving 54% of the migrating population, significantly increases NOx and SO2 emissions because of high urban indirect per-capita emissions from consumption and investment. RU migration influences negligibly primary PM2.5 emissions reflecting the small rural-urban difference in per-capita emissions. Interestingly, UU migration, mostly from inland to coastal provinces, leads to a slight emission decrease for the three pollutants, attributable to the greener development in coastal cities. A significant emission growth can be traced back to heavy and utility industries, suggesting that future emission control of these sectors should reduce the exposure to air pollution of the growing urban population.