| In recent years, with the development of industry and the rapidly increase in the number of cars, most areas arised a large scope haze weather in frequently, which brought serious impact on atmospheric quality, people’s health and traffic security. Chongqing, as one of the four municipalities directly governed under the Chinese Central Government, is an industry base in southwest China and locates in a special basin position. Those factors lead to poor dispersion of pollutants in the air. So, atmospheric pollution in Chongqing was serious in the past years. However, at present, there has seldom research reported about the characteristics and transformation of atmospheric pollutants in the urban area of Beibei district of Chongqing. Beibei, as a main district of Chongqing, locates in the north of Chongqing, often called the back garden, and it is also a national environmental protection model city and a more liveable city of Chongqing. So, the atmospheric quality directly affect the health and quality of life of local residents. In order to understand the regional atmospheric pollution condition, the concentrations of NOx, O3, SO2and PM2.5were measured by automatic on-line continuous monitoring equipments from Jan.2012to Feb.2013and air samples were collected to determine the composition of VOCs(Volatile Organic Compounds) in regularly. The daily and seasonal changes in the concentration of air pollution, the sources and the influencing factors such as meteorological elements were analyzed. It will provide a scientific basis for control and management atmospheric pollutants in the region. The main conclusions of this research are as follows:(1)The results showed that the concentration of the pollutants often exceeded the corresponding values of the new National Ambient Air Quality Standards (GB3095-2012) except SO2. Of these pollutants, PM2.5was the most serious one in this area. The concentrations of the atmospheric pollutants had significant seasonal variation. The concentrations of O3and Ox were both highest in summer and lowest in winter. The average concentrations of O3were (36.1±19.2),(48.8±32.6),(29.8±28.6) and (18.2±15.8) ug·m-3, and of Ox were (77.6±20.6),(91.3±37.6),(77.5±30.6) and (69.4±18.2) μg·m-3in spring, summer, autumn and winter in2012, respectively. The concentrations of NOx appeared higher in winter and lower in summer, the average concentrations of NO2and NOx are (11.8±9.4),(42.3±13.1) and (54.1±20.8) μg·m-3in spring,(8.2±4.9),(40.5±9.9) and (48.7±12.6) μg·m-3in summer,(20.7±17.1),(47.2±14.1) and (67.9±25.5) μg·m-3in autumn, and (30.4t±25.1),(51.2±15.9),(81.6±37.9) μg·m-3in winter. The concentrations of SO2appeared higher in spring and winter, lower in summer and autumn. The concentrations of SO2were (50.5±23.3),(26.3±16.7),(38.8±18.4) and (53.7±23.4) ug·m-3in spring, summer, autumn and winter, respectively. The concentrations of PM2.5appeared higher in winter and changed smoothly in other seasons, with the average concentration of (61.4±28.5),(68.1±32.5),(61.9±27.1) and (89.6±44.2)μg·m-3in spring, summer, autumn and winter, respectively.(2) The curves of diurnal variations of O3, Ox, NO, NOx and SO2all showed single peak. However, the time of the peak values varied for the different pollutants,16:00for O3and Ox,8:00-11:00for NO, NOx and SO2. The diurnal variations of NO2and PM2.5were similar with two peaks which appeared in the morning and at night, respectively. Moreover, the diurnal ranges of O3and Ox concentrations were much wider in summer, but which were in winter for NO, NO2, NOx, SO2and PM2.5. There was no difference in diurnal pattern of NO between weekends and weekdays, the concentrations of N2O in weekdays were much higher than in weekends, but with O3the opposite was the case. Correlation analysis indicated that O3concentration was positively correlated with temperature and wind speed, while inversely with relative humidity. However, NOx had the direct opposite of O3. PM2.5concentration was negatively correlated with temperature and wind speed, while positively with relative humidity. SO2concentration had different correlations with the meteorological parameters in the different seasons. In addition, wind direction was an important factor affecting the concentrations of the atmospheric pollutants.(3)78species of VOCs were detected in this study, of which including25species of alkanes,15species of olefins,28species of aromatic hydrocarbonms and10species of halogenated hydrocarbons. The results showed that the first highest seven species of VOCs according to the order of annual average concentration in the atmosphere of Beibei were: Dichloromethane(3.08×10-9),Benzene(2.09×10-9),Isopentane(1.85×10-9),Toluene(1.51×10-9), Propane(1.51×10-9), M/p-xylene (1.43×10-9) and Styrene (1.39×1O-9). The concentration of TVOCs(Total Volatile Organic Compounds) in the atmosphere of Beibei was33.89×10-9during the measuring period, and the seasonal variation was obviously with the order of spring (42.57×10-9)>autumn(33.89×10-9)>winter (31.91×10-9)>summer (27.04×10-9). In the composition of TVOCs, alkanes and aromatic hydrocarbons provided the largest contribution to TVOCs (31.5%and30.7%), followed by halogenated hydrocarbon, accounting for27.4%, and the last one was olefins, with only10.4%. By means of ozone formation potential, the analysis results showed that olefins and aromatic hydrocarbon compounds were the two important materials which made the biggest contribution to the formation of ozone in the atmosphere of Beibei. We further analyzed the sources of VOCs. |
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