ABSTRACT
Based on the pollutant data provided by the environmental monitoring stations and the routine observation data of 11 national meteorological stations in Jiangxi Province from 2016 to 2019, the characteristics of ozone pollution and the relationships with meteorological factors were investigated in this study. The results showed that ozone pollution has become increasingly severe in Jiangxi Province in recent years. The annual mean concentration of ozone in Jiangxi Province (the maximum daily 8 h average) was 80.1 µg·m-3 in 2016 and reached up to 98.2 µg·m-3 in 2019, with an average annual growth rate of 6 µg·m-3. The number of over-standard days of ozone was 475 d, accounting for 72.6% of 2019 in Jiangxi Province. The average concentrations observed in summer were higher than those observed in the other seasons during 2016 to 2018, but in 2019, higher ozone concentrations were observed in autumn owing to the lower precipitation, more sufficient sunshine, and the resulting higher air temperature. Overall, the ozone concentrations were found to be positively correlated with air temperature and sunshine but negatively correlated with relative humidity in Jiangxi Province. A high ozone concentration usually appeared with an air temperature higher than 30â, relative humidity of 20%-40%, and wind speed of 2-3 m·s-1. The spatial distribution of the ozone concentrations exhibited distinct characteristics with higher values observed in southern Jiangxi relative to those in the northern areas and lower values in northeastern Jiangxi compared with those in other regions. More serious ozone pollution was found in Ganzhou among the 11 cities in Jiangxi Province, with the highest annual concentration of 104.2 µg·m-3 observed in 2019. The results of the model analyses, including the HYSPLIT backward trajectory model and potential source contribution function model, indicated that there was a significant difference in the potential source contribution of ozone pollution in Ganzhou on seasonal scales, specifically in central Guangdong and the northwest of Jiangxi Province in spring, the northwest parts of Jiangxi Province in summer, and the north of Guangdong and central Anhui Province in autumn.
ABSTRACT
Direct observation of urban atmospheric CO2 concentration is vital for the research in the contribution of anthropogenic activity to the atmospheric abundance since cities are important CO2 sources. The observations of the atmospheric CO2 concentration at multiple sites/heights can help us learn more about the temporal and spatial patterns and influencing mechanisms. In this study, the CO2 concentration was observed at 5 sites (east, west, south, north and middle) in the main city area of Nanjing from July 18 to 25, 2014, and the vertical profile of atmospheric CO2 concentration was measured in the middle site at 3 heights (30 m, 65 m and 110 m). The results indicated that: (1) An obvious vertical CO2 gradient was found, with higher CO2 concentration [molar fraction of 427. 3 x 10(-6) (±18. 2 x 10(-6))] in the lower layer due to the strong influences of anthropogenic emissions, and lower CO2 concentration in the upper layers [411. 8 x 10(-6) (±15. 0 x 10(-6)) and 410. 9 x 10(-6) (±14. 6 x 10(-6)) at 65 and 110 m respectively] for the well-mixed condition. The CO2 concentration was higher and the vertical gradient was larger when the atmosphere was stable. (2) The spatial distribution pattern of CO2 concentration was dominated by wind and atmospheric stability. During the observation, the CO2 concentration in the southwest was higher than that in the northeast region with the CO2 concentration difference of 7. 8 x 10(-6), because the northwest wind was prevalent. And the CO2 concentration difference reduced with increasing wind speed since stronger wind diluted CO2 more efficiently. The more stable the atmosphere was, the higher the CO2 concentration was. (3) An obvious diurnal variation of CO2 concentration was shown in the 5 sites. A peak value occurred during the morning rush hours, the valley value occurred around 17:00 (Local time) and another high value occurred around 19:00 because of evening rush hour sometimes.
