| dc.description |
Air pollution data, air quality index (AQI) data and L band sounding data of Wuhan City from January 1 to February
28, 2015, were used in this study. Since air quality is mainly
determined by the condition of the atmospheric boundary layer
structure (ABLS), a detailed analysis was carried out in order to
determine the evolution of this layer and its relationship with air
quality. During the investigation period, the highest value of AQI
was 307 on January 26 and the lowest was 33 on February 28
indicating ‘severe pollution’ and ‘excellent’ air quality, respec tively. The concentrations of PM2.5 during the days with the
highest and lowest AQI were 142.61 and 9.78 μg/m3
, respec tively. The percentage of days in which the ratio of PM2.5 in
PM10 was more than half was 83.05% which means that the
greater portion of pollutants were composed of smaller particles.
Moreover, four PM2.5 episodes (three or more consecutive days
of PM2.5 ≥ 75 μg/m3
) were identified and the average percentage
of elementary carbon (EC) in PM2.5 during episode 1 (prior to
the episode) was 6.274% (6.276%), episode 2 was 5.634%
(7.174%), and episode 4 was 4.067% (7.785%). Higher concen trations of EC prior to episodes suggest biomass burning to be
one of the reasons for episodes occurrence. Analysis of the
ABLS during polluted days show that the boundary layer was
dry and warm and had weak low-level wind and dominance of northerly winds. A different scenario is seen on clean days as the
boundary layer is observed to be wet and cool, and there is
dominance of strong winds. Back trajectory analysis results
show that polluted days were dominated by air mass from north
China while on clean days, the dominant air masses were from
East China Sea, Mongolia, and west China. |
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