Chemical characteristics of PM2:5 during a typical haze episode in Guangzhou
TAN Jihua , DUAN Jingchun , HE Kebin , MA Yongliang , DUAN Fengkui , CHEN Yuan , FU Jiamo
DOI:
Received May 28, 2008,Revised March 03, 2009, Accepted , Available online
Volume 21,2009,Pages 774-781
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The chemical characteristics (water-soluble ions and carbonaceous species) of PM2:5 in Guangzhou were measured during a typical
haze episode. Most of the chemical species in PM2:5 showed significant di erence between normal and haze days. The highest
contributors to PM2:5 were organic carbon (OC), nitrate, and sulfate in haze days and were OC, sulfate, and elemental carbon (EC)
in normal days. The concentrations of secondary species such as, NO3??, SO4
2??, and NH4
+ in haze days were 6.5, 3.9, and 5.3 times
higher than those in normal days, respectively, while primary species (EC, Ca2+, K+) show similar increase from normal to haze days by
a factor about 2.2–2.4. OC/EC ratio ranged from 2.8 to 6.2 with an average of 4.7 and the estimation on a minimum OC/EC ratio showed
that SOC (secondary organic carbon) accounted more than 36.6% for the total organic carbon in haze days. The significantly increase in
the secondary species (SOC, NO3??, SO4
2??, and NH4
+), especially in NO3??, caused the worst air quality in this region. Simultaneously,
the result illustrated that the serious air pollution in haze episodes was strongly correlated with the meteorological conditions. During
the sampling periods, air pollution and visibility had a good relationship with the air mass transport distance; the shorter air masses
transport distance, the worse air quality and visibility in Guangzhou, indicating the strong domination of local sources contributing to
haze formation. High concentration of the secondary aerosol in haze episodes was likely due to the higher oxidation rates of sulfur and
nitrogen species.
