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Atmosphere 2018, 9(9), 359;

Characteristics of Atmospheric Boundary Layer Structure during PM2.5 and Ozone Pollution Events in Wuhan, China

Institute of Atmospheric Physics and Atmospheric Environment, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
Solomon Mahlangu College of Science and Education, Department of Geography and Environmental Studies, Sokoine University of Agriculture, Morogoro P.O. Box 3038, Tanzania
Author to whom correspondence should be addressed.
Received: 17 July 2018 / Revised: 30 August 2018 / Accepted: 7 September 2018 / Published: 18 September 2018
(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)
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In this study, we investigated six air pollutants from 21 monitoring stations scattered throughout Wuhan city by analyzing meteorological variables in the atmospheric boundary layer (ABL) and air mass backward trajectories from HYSPLIT during the pollution events. Together with this, ground meteorological variables were also used throughout the investigation period: 1 December 2015 to 30 November 2016. Analysis results during this period show that the city was polluted in winter by PM2.5 (particulate matter with aerodynamics of less than 2.5 microns) and in summer by ozone (O3). The most polluted day during the investigation period was 25 December 2015 with an air quality index (AQI) of 330 which indicates ‘severe pollution’, while the cleanest day was 26 August 2016 with an AQI of 27 indicating ‘excellent’ air quality. The average concentration of PM2.5 (O3) on the most polluted day was 265.04 (135.82) µg/m3 and 9.10 (86.40) µg/m3 on the cleanest day. Moreover, the percentage of days which exceeded the daily average limit of NO2, PM10, PM2.5, and O3 for the whole year was 2.46%, 14.48%, 23.50%, and 39.07%, respectively, while SO2 and CO were found to be below the set daily limit. The analysis of ABL during PM2.5 pollution events showed the existence of a strong inversion layer, low relative humidity, and calm wind. These observed conditions are not favorable for horizontal and vertical dispersion of air pollutants and therefore result in pollutant accumulation. Likewise, ozone pollution events were accompanied by extended sunshine hours, high temperature, a calm wind, a strongly suspended inversion layer, and zero recorded rainfall. These general characteristics are favorable for photochemical production of ozone and accumulation of pollutants. Apart from the conditions of ABL, the results from backward trajectories suggest trans-boundary movement of air masses to be one of the important factors which determines the air quality of Wuhan. View Full-Text
Keywords: atmospheric boundary layer; air quality index; PM2.5 pollution; ozone pollution; trans-boundary movement atmospheric boundary layer; air quality index; PM2.5 pollution; ozone pollution; trans-boundary movement

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Mbululo, Y.; Qin, J.; Hong, J.; Yuan, Z. Characteristics of Atmospheric Boundary Layer Structure during PM2.5 and Ozone Pollution Events in Wuhan, China. Atmosphere 2018, 9, 359.

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