1. Chemical composition of ambient PM2
Chemical composition of ambient PM2.5 over China and relationship to precursor emissions during 2005–2012
Guannan Geng, Qiang Zhang, Dan Tong, Meng Li, Yixuan Zheng, Siwen Wang, and Kebin He
May 3, 2017

2. Severe PM2.5 pollution over China
Primary pollutants in 2013
Mortality
PM2.5 concentrations in 2013
above 100μg/m3
China
(Apte et al., ES&T, 2016)

3. Datasets used in this study
Ground measurements
National monitoring network is unavailable between 2005 and 2012
Observations collected from literatures
Satellite-based PM2.5 composition
( )
Satellite AOD data from MODIS and MISR instrument
GEOS-Chem model
Bottom-up emissions
MEIC inventory
𝑨𝑶𝑫 𝒔𝒂𝒕𝒆𝒍𝒍𝒊𝒕𝒆 × 𝑷𝑴 𝟐.𝟓_𝒎𝒐𝒅𝒆𝒍𝒆𝒅 ( 𝑪𝒐𝒎𝒑𝒐𝒏𝒆𝒕 𝒎𝒐𝒅𝒆𝒍𝒆𝒅 ) 𝑨𝑶𝑫 𝒎𝒐𝒅𝒆𝒍𝒆𝒅
𝑷𝑴 𝟐.𝟓_𝒔𝒂𝒕𝒆𝒍𝒍𝒊𝒕𝒆
𝑪𝒐𝒎𝒑𝒐𝒏𝒆𝒕 𝒔𝒂𝒕𝒆𝒍𝒍𝒊𝒕𝒆
(Geng et al., RSE, 2015)
(Philip et al., ES&T, 2014)

4. Evaluation
(Geng et al., ACPD, 2017)

5. Spatial distribution of PM2.5 composition

6. PM2.5 speciation for 20 major cities across China

7. Temporal variations in PM2.5
National population-weighted mean PM2.5 concentration increased from 2005 to 2007 and subsequently decreased from 2007 to 2012

8. Temporal variations in PM2.5 composition
Sulfate
Nitrate
Ammonium OM BC
Dust
Sea salt
-2.36%/yr
+3.39%/yr

9. Temporal variations in SNA
Sulfate concentration increased by 10.7% from 2005–2006 and then decreased by 4.3% per year from 2006–2012.
The decrease of sulfate concentration is partly offset by the increase of nitrate concentration: population-weighted mean nitrate concentration increased by 3.4% per year during 2005–2012.

10. Relationship between PM2.5 composition and precursor emissions
The changes in sulfate and nitrate concentrations were in line with the changes in SO2 and NOx emissions during the same period.

11. Emission driving forces
12th Five Year Plan:
Reduce SO2 by 8%
Reduce NOx by 10%
11th Five Year Plan:
Reduce SO2 by 10%
2006
2011

12. Region-specific emission change rates

13. Summary
Variations in PM2.5 concentrations are mainly driven by the changes in sulfate and nitrate concentrations.
The decrease of sulfate concentration is partly offset by the increase of nitrate concentration.
Synchronized abatement of emissions for multi-pollutants are necessary for reducing ambient PM2.5 concentrations over China

14. Model Evaluation