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

Abstract

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.

Chemical Composition and Deposition Fluxes of Water-Soluble Inorganic Ions on Dry and Wet Deposition Samples in Wuhan, China

“…These general characteristics during high (low) concentration of PM 2.5 are unfavourable (favourable) for dispersion and mixing of aerosols. Corroborated results to this have been reported in our previous works [21,26].…”

“…Wuhan, which is the capital city of Hubei Province (Longitude 113°41′~115°05′ E and Latitude 29°58′~31°22′ N) had a population of 10.91 million people in 2017. A number of studies [19,20,21,22,23,24,25,26] reported that this city experienced serious PM 2.5 pollution events in recent years. Nevertheless, little has been done to study WSII which are the main constituents of PM 2.5 .…”

Characteristics of Ozone Pollution, Regional Distribution and Causes during 2014–2018 in Shandong Province, East China

“…Studies in other regions have also confirmed the impact of monsoon on ozone concentrations. The ozone concentrations in Beijing, the YRD, and Wuhan are all unimodal [14,44,45]. Similar to the situation in Shandong province, the peak concentrations in Beijing and the YRD occurred prior to impacts of the monsoon, while the peak concentration in Wuhan occurred after the monsoon.…”

Daytime Evolution of Lower Atmospheric Boundary Layer Structure: Comparative Observations between a 307-m Meteorological Tower and a Rotary-Wing UAV

“…Vertical structure of the lower atmospheric boundary layer (ABL) plays a crucial role in determining the evolution of near-surface wind and thermal environments as well as local air quality. The surface layer of the ABL, defined as the lower 10% of the total ABL, exhibits large gradients of atmospheric momentum and heat [1][2][3][4][5]. Nocturnal low-level jet and temperature inversion are well-known examples of wind and thermal phenomena, respectively, which occur in the lower ABL [6,7].…”