Emission-driven changes in anthropogenic aerosol concentrations in China during 1970-2010 and its implications for PM2.5 control policy

There are open debates on whether the amount of emission reduction could fulfil the anthropogenic PM2.5 (particulate matter smaller than 2.5 mu m) mitigation in China. This study evaluated the long-term historical aerosol simulations for 1970-2010 in eastern China from three models (CACTUS, WRF-CMAQ, and GISS-E2-R). We introduced 95% Confidence Interval of n-year Moving Difference (n-year CIMD, n = 1...10) in the long-term simulated PM2.5 concentrations to determine how long PM2.5 change in history is significant and how many increases in historical emissions raised the amount of PM2.5 that we want to reduce today. The results show that the annual trends for the simulated PM2.5 ranged from 0.42 to 0.72 mu g m(-3) year(-1) lying within the 95% confidence intervals for the trend in the satellite-derived PM2.5. There was a reasonable change in PM2.5 chemical compositions with increasing nitrate and declining OA mass fractions from 1970 to 2010. Particulates were more neutralized as the quick increases in ammonia and the control on SO2 emissions. The significant analysis of changes indicates that at least a 5-year CIMD for PM2.5 could be distinguished from the PM2.5 fluctuations due to emission uncertainties and meteorological interannual variations. At least a 10-year CIMD for PM2.5 could be distinguished from the multi-model uncertainties. The historical relationship between PM2.5 and emissions suggests that the minimum PM2.5 reduction targeted in the China's 12th Five-Year Plan (FYP; 2011-2015) would require the emission changes compared with 2010 in SO2, NOx, and NH3 by 41%, 29%, and 42%, respectively. The amounts were larger than the emission reduction planned for the 12th FYP. This suggests that the past emission policies and PM2.5 control pledges were incompatible and a stricter emission reduction is needed to attain the 13th FYP (2016-2020).