Fig. 1.

(A) Interannual trends in SO₂, NO_x, and NH₃ emissions in China during 2005–2015. SO₂ emissions were provided by the Ministry of Ecology and Environment of China (MEE; www.mee.gov.cn/), Lu et al. (35), and Multiresolution Emission Inventory for China; NOx emissions were derived from MEE and Liu et al. (12); and NH₃ emissions were derived from Kang et al. (25). (B) Interannual trends in wet deposition (mean ± SD) of sulfate, nitrate, and ammonium averaged over four Acid Deposition Monitoring Network in East Asia stations (Jinyunshan, Shizhan, Xiaoping, and Xiangzhou) in China. (C) Normalized vertical column densities (VCDs) of SO₂ and NO₂ retrieved from ozone monitoring instrument measurements over China relative to the 2005 levels. (D) Ground-based concentrations of SO₂ and NO₂ averaged over 31 cities in China. These annual averaged values for each city were provided by the China Environmental Statistics Yearbook (www.stats.gov.cn/).