Abstract
To comprehensively explore the transport of air pollutants, one-year continuous online observation of PM2.5 was conducted from 1 April 2015 to 31 March 2016 at Dianshan Lake, a suburban junction at the central of Yangtze River Delta. The chemical species of PM2.5 samples mainly focused on Organic carbon (OC), Elemental carbon (EC) and Water-Soluble Inorganic Ions (WSIIs). The annual average of PM2.5 concentration was 59.8 ± 31.7 µg·m−3, 1.7 times higher than the Chinese National Ambient Air Quality Standards (CNAAQS) (35 µg·m−3). SNA (SO42−, NO3− and NH4+) was the most dominated species of PM2.5 total WSIIs, accounting for 51% of PM2.5. PM2.5 and all of its chemical species shared the same seasonal variations with higher concentration in winter and spring, lower in autumn and summer. The higher NO3−/EC and NOR occurred in winter suggested that intensive secondary formation of nitrate contributed to the higher levels of PM2.5. Cluster analysis based on 72-h backward air trajectory showed that the air mass cluster from nearby inland cities, including Zhejiang, Anhui and Jiangxi Provinces contributed mostly to the total trajectories. Furtherly, potential source contribution function (PSCF) analysis revealed that local sources, namely the emissions in the Yangtze River, were the primary sources. During haze pollution, NO3− was the most important fraction of PM2.5 and the heterogeneous formation of nitrate became conspicuous. All the results suggested that the anthropogenic emissions (such as traffic exhaust) was responsible for the relatively high level of PM2.5 at this monitoring station.
Highlights
Due to the rapid industrialization and urbanization, China has suffered severe haze pollution during the past decades, which is characterized by extremely high levels of fine particulate matter (PM2.5 ) [1,2,3]
Potential source contribution function (PSCF) analysis revealed that local sources, namely the emissions in the Yangtze River, were the primary sources
All the results suggested that the anthropogenic emissions was responsible for the relatively high level of PM2.5 at this monitoring station
Summary
Due to the rapid industrialization and urbanization, China has suffered severe haze pollution during the past decades, which is characterized by extremely high levels of fine particulate matter (PM2.5 ) [1,2,3]. The chemical constitutes of PM2.5 are extremely complexed, including the main species of OC, EC and WSIIs such as sulfate (SO4 2− ), nitrate (NO3 − ) and ammonium (NH4 + ), namely SNA [7,8]. Except for primary emissions, chemical conversion of gaseous pollutants is another important sources. The formation mechanism of SNA depends on related precursor pollutants (SO2 , NO2 and NH3 ), oxidative state of atmosphere and the meteorological factors [8,9]. The main pathways for the formation of sulfate and nitrate was the gas- or liquid-phase reactions of SO2 and NO2. Homogeneous gas-phase reaction of SO2 with OH, H2 O2 or catalytic metals (such as Fe(III)
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