Abstract
As the new core region of the haze pollution, the terrain effect of sub-basin and water networks over the Twin-Hu Basin (THB) in the Yangtze River Middle-Reach (YRMR) had great impacts on the variations and distributions of air pollutants. In this study, trace gases (NH3, HNO3, and HCl), water-soluble ions (WSIs), organic carbon (OC), and elemental carbon (EC) were measured in PM2.5 from 9 January to 27 January 2018, in Wuhan using monitoring for aerosols and gases (MARGA) and a semi-continuous OC/EC analyzer (Model RT-4). The characteristics of air pollutants during a haze episode were discussed, and the PM2.5 sources were quantitatively analyzed on haze and non-haze days using the principal component analysis/absolute principal component scores (PCA/APCS) model. The average PM2.5 concentration was 122.61 μg·m−3 on haze days, which was 2.20 times greater than it was on non-haze days. The concentrations of secondary water soluble ions (WSIs) including NO3−, SO42−, and NH4+ increased sharply on haze days, which accounted for 91.61% of the total WSIs and were 2.43 times larger than the values on non-haze days. The heterogeneous oxidation reactions of NO2 and SO2 during haze episodes were proven to be the major sources of sulfate and nitrate in PM2.5. On haze days, the concentrations of EC, primary organic carbon (POC), and secondary organic carbon (SOC) were 1.68, 1.69, and 1.34 times larger than those on non-haze days, the CO, HNO3, and NH3 concentrations enhanced and relatively low SO2, O3, and HNO2 levels were observed on haze days. The diurnal variations of different pollutants distinctly varied on haze days. The PM2.5 in Wuhan primarily originated from the secondary formation, combustion, dust, industry, and vehicle exhaust sources. The source contributions of the secondary formation + combustion sources to PM2.5 on haze days were 2.79 times larger than the level on non-haze days. The contribution of the vehicle exhaust + combustion source on haze days were 0.59 times the value on non-haze days. This description is supported by a summary of how pollutant concentrations and patterns vary in the THB compared to the variations in other pollution regions in China, which have been more completely described.
Highlights
Over the past several decades, rapid industrialization and urbanization, as well as a continuous increase of vehicle holdings, have caused unceasing deterioration of the air quality in China, which can reduce the visibility and impair human health, damaging the sustainable development of Atmosphere 2019, 10, 397; doi:10.3390/atmos10070397 www.mdpi.com/journal/atmosphereAtmosphere 2019, 10, 397 the economy and society [1,2,3,4,5]
The concentrations of elemental carbon (EC), primary organic carbon (POC), and secondary organic carbon (SOC) were 1.68, 1.69, and 1.34 times larger than those on non-haze days, the CO, HNO3, and NH3 concentrations enhanced and relatively low SO2, O3, and HNO2 levels were observed on haze days
It can be seen that the O3 concentration and visibility were both high during the daytime during the period of 9–14 January, and the high temperatures and low relative humidity (RH) levels were responsible for the daytime O3 formation
Summary
Over the past several decades, rapid industrialization and urbanization, as well as a continuous increase of vehicle holdings, have caused unceasing deterioration of the air quality in China, which can reduce the visibility and impair human health, damaging the sustainable development of Atmosphere 2019, 10, 397; doi:10.3390/atmos10070397 www.mdpi.com/journal/atmosphereAtmosphere 2019, 10, 397 the economy and society [1,2,3,4,5]. In China, heavy pollution events are traditionally centralized in four regions including the North China Plain (NCP), Yangtze River Delta (YRD), Pearl River Delta (PRD), and Sichuan Basin (SB) [6,7,8]. The spatiotemporal variations of air pollutants have changed in recent years. The PM2.5 concentration in the PRD has declined in recent years and was down to 32 μg·m−3 in 2016, meeting the Grade I National Ambient Air Quality Standard (
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