Abstract
Ozone (O3) pollution has become one of the most challenging problems in China, and high O3 concentrations have been a major air quality issue in Changchun. Based on continuous observation data of surface ozone concentrations from ten automatic air monitoring stations and meteorological data from the meteorological bureau in Changchun, the temporal and spatial variations of the O3 concentration and its relationships with meteorological factors were analyzed by correlation analysis during the period of 2013–2017. The results showed the following: A single apex model of the annual mean O3 concentrations of the daily maximum 8 h average (MDA8) was found from the data for 2013 to 2017 in Changchun, with the highest MDA8 O3 concentrations in 2015 and a slight decline from then until 2017. The O3 concentrations in the suburban areas and the south of Changchun were higher than those downtown and north of the city. The seasonal variation of O3 concentrations was obvious, following the order summer > spring > autumn > winter, which was similar to the results of neighboring cities and provinces in Changchun. The days on which O3 concentrations exceeded the standard were concentrated in summer and spring, and the total number of ozone excess days was 91 days; the maximum number of ozone excess days was in 2015. The O3 concentration exceeded the standard in Changchun mainly in March–August, and its monthly mean value curve showed a bimodal type in which the highest values appeared in May and July, while the lowest values appeared in December. The diurnal pattern of ozone showed a single peak mode, and the peak value usually appeared at 14:00–16:00 while the minimum value appeared at 07:00–08:00. O3 concentrations in Changchun and the six selected pollutants CO, NO, NO2, NOx, PM10, and PM2.5 were negatively correlated. Higher temperature is a necessary synoptic condition for ozone pollution in Changchun: when the temperature rose, O3 concentrations increased significantly; further, O3 concentrations were negatively correlated with relative humidity and atmospheric pressure and were positively correlated with temperature and solar radiation. The O3 concentrations were highest when the wind scale approached 14~20 km/h and the wind direction was S. Combined with the research results in the surrounding areas of Changchun, it is indicated that there may be an ozone contribution from south of Changchun through long-range pollution transport and tropospheric subsidence.
Highlights
Ozone and fine particulate matter, as secondary pollutants, are considered to be two main atmospheric contaminants that dramatically affect the current environmental quality [1]
Research over the Eastern Mediterranean indicated that the main origin of these high background ozone levels is tropospheric ozone subsidence, which seems to be strongly related with specific synoptic meteorological conditions [19]
It is shown that the ozone concentration in the periphery of Changchun is higher than that in the center of the city, and the ozone concentration in the south of the city is higher than that in the north of the city
Summary
Ozone and fine particulate matter, as secondary pollutants, are considered to be two main atmospheric contaminants that dramatically affect the current environmental quality [1]. The formation of ozone is mainly controlled by precursor emissions and photochemical processes, but tropospheric ozone entrainment influences the surface ozone, resulting in enhancement of its concentration [9]. It has been shown that the regional background ozone levels in the free troposphere and the boundary layer during summer contribute on average to the most part of the surface ozone levels measured in large urban areas like Athens [12]. Meteorological changes can affect recent and future trends in ozone and its precursors [15], and ozone pollution events are often caused by high-intensity emissions and adverse meteorological conditions [16]. Research over the Eastern Mediterranean indicated that the main origin of these high background ozone levels is tropospheric ozone subsidence, which seems to be strongly related with specific synoptic meteorological conditions [19]. Ozone monitoring data from Changchun, the capital of Jilin province, from 2013 to 2017 were used to analyze the variation characteristics and main causes of the ozone concentration in Changchun in combination with the relationship between various pollutants and meteorological factors
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