The reaction mechanism, measurement and simulation models of secondary particles in
atmospheric PM2.5: A review
SUN Yangyang1, CHEN Linghong1, ZHU Jie1, ZUO Lei1, JIAO Li2, GAO Xiang1, CEN Kefa1
1
2
State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
Hangzhou Environmental Monitoring Center, Hangzhou 310007, China
ABSTRACT
The toxicity and damage to environment of secondary particles in atmospheric PM2.5 has been the focus for the
public in China. Reaction mechanism of secondary PM2.5 was reviewed including atmospheric photochemical
reactions of secondary organic carbon (SOA) between VOCs and oxidants such as OH, NOx, O3, transformation
mechanism of benzene, phenol and diolefin, and heterogeneous reactions of SO2 and NOx on mineral dust in
urban areas. Three theoretical models were illustrated to determine the contribution of secondary particles from
different types of emission sources. Chemical Mass Balance model (CMB) as source apportionment receptor
models calculates the linear summation of each source concentration contribution to compute the secondary
particles concentration of the receptor. For uncertain sources, statistical methods are adopted which can give birth
to other receptors such as positive matrix factorization method (PMF). Organic tracer method is introduced in
receptor models to study secondary organic particulates. In Community Multi-scale Air Quality (CMAQ)
modeling system, photochemical reactions are coupled with meteorological data and gridded emission inventories.
The methods to measure miscellaneous secondary particles were also discussed. Inorganic compound such as
sulphate, nitrate and chloride are analysed after water extraction with ion chromatography. Carbonaceous
component is divided into organic carbon (OC) and elemental carbon (EC), the latter is considered inert and
invariable in atmosphere. Thermal-Optical method is adopted for the OC/EC analysis. Other prevalent instrument
such as GC/MS is also introduced to measure different SOA. In the end, control strategies of secondary PM2.5
were discussed.
KEYWORDS
Secondary PM2.5, VOCs, OC/EC, reaction mechanism, measurement method, control strategy
ACKNOWLEDGEMENT
This work is supported by the National Basic Research Program of China (grants 2009CB219802), the National
Science Foundation (51206144), the Natural Science Foundation of Zhejiang province (LY12E06003), and the
Program of Introducing Talents of Discipline to University (B08026).