Abstract. To evaluate the improved emission estimates from online monitoring, we
applied the Models-3/CMAQ (Community Multiscale Air Quality) system to
simulate the air quality of the Yangtze River Delta (YRD) region using two
emission inventories with and without incorporated data from continuous emission
monitoring systems (CEMSs) at coal-fired power plants (cases 1 and 2,
respectively). The normalized mean biases (NMBs) between the observed and
simulated hourly concentrations of SO2, NO2, O3, and
PM2.5 in case 2 were −3.1 %, 56.3 %, −19.5 %, and −1.4 %, all
smaller in absolute value than those in case 1 at 8.2 %, 68.9 %,
−24.6 %, and 7.6 %, respectively. The results indicate that incorporation
of CEMS data in the emission inventory reduced the biases between simulation
and observation and could better reflect the actual sources of regional air
pollution. Based on the CEMS data, the air quality changes and corresponding
health impacts were quantified for different implementation levels of
China's recent “ultra-low” emission policy. If the coal-fired power sector
met the requirement alone (case 3), the differences in the simulated monthly
SO2, NO2, O3, and PM2.5 concentrations compared to those
of case 2, our base case for policy comparisons, would be less than 7 % for
all pollutants. The result implies a minor benefit of ultra-low emission
control if implemented in the power sector alone, which is attributed to its limited
contribution to the total emissions in the YRD after years of pollution
control (11 %, 7 %, and 2 % of SO2, NOX, and primary particle
matter (PM) in case 2, respectively). If the ultra-low emission policy was
enacted at both power plants and selected industrial sources including
boilers, cement, and iron and steel factories (case 4), the simulated
SO2, NO2, and PM2.5 concentrations compared to the base
case would be 33 %–64 %, 16 %–23 %, and 6 %–22 % lower, respectively,
depending on the month (January, April, July, and October 2015). Combining
CMAQ and the Integrated Exposure Response (IER) model, we further estimated
that 305 deaths and 8744 years of life loss (YLL) attributable to PM2.5
exposure could be avoided with the implementation of the ultra-low emission
policy in the power sector in the YRD region. The analogous values would be
much higher, at 10 651 deaths and 316 562 YLL avoided, if both power and
industrial sectors met the ultra-low emission limits. In order to improve
regional air quality and to reduce human health risk effectively,
coordinated control of multiple sources should be implemented, and the
ultra-low emission policy should be substantially expanded to major emission
sources in industries other than the power industry.