Comparison And Analysis Of Ozone And Its Precursors In Urban And Rural Sites In Nanjing

Atmospheric environment has attracted much attention, it’s not only related to our health, but also a threat to the natural environment for human survival. Based on Nanjing ground observations, ozone and its precursors in Nanjing are discussed. Combined with the climatic factors, the difference of ozone concentration in each season is also analysised. The difference between Nanjing suburb and rural pollutants is discussed based on the EMS system and the DO AS AQM. Using the OZIPR mode to analysis the case in May162011, the results show that:1. Ozone concentration in Nanjing has obvious seasonal variation, the highest value of35.5ppbv appears in summer, and the minimum of21.6ppbv appears in winter. The daily maximum ozone concentration appears about15:00, the maximum in spring and the minimum in winter. The Weekend effect in Nanjing is not obvious as other cities, the ozone concentration is almost the same in weekend and weekday, but the ozone concentration has single peak during a day. The maximum appears about15:00, the maximum appears in spring and the minimum appears in winter, the negative correlation between ozone and its precursors:NOx、NO2、NO、 CO, is very well, the correlation coefficient R2is0.8、0.6、0.7、0.7. The ozone concentration is related to the trace gases and affected by meteorological factors。Temperature、sunshine hours and precipitation are the main factor which affect the near-ground ozone concentration in Nanjing. With the influence of long hour’s sunshine and low precipitation in May, the ozone concentration has its peak. The main source of pollution leading the increase of ozone is mainly from the south, the regional transmission also plays significant roles affecting the ozone concentration.2. The result of comparison between city and suburb shows that:the O3concentration is maximum and changes more frequently in sunny days, but relatively low in cloudy and precipitation days. The peak is47.6%and58.1%lower compared with sunny days. The ozone concentration in suburb during cloudy and precipitation days is relatively35.2%and36.0%lower, O3concentration is higher in precipitation days than cloudy days. Hour value of O3concentration is higher in the city, the time when lowest value appears in suburb is in advance, mainly because the petrochemical companies in Nanjing suburbs and atmospheric oxidation and O3concentration is affected by reverse photochemical reactions at night. The amplitude of Ox (NO2+O3)’x concentration diurnal variation is maximum in the summer of the city, and minimum in the suburb in the spring. Ox is mainly affected by the concentration diurnal variation of O3. High concentration of Ox and low concentration of NOx appears during the day in the spring, long-distance transmission is the main source of Ox concentration, high concentrations of Ox happens at night when the NOx concentration is also higher, indicating that Ox is affected by local pollution emissions, summer and spring have the similar characteristics. 3. The ozone concentration is not well related to the VOCs concentration, the ozone concentration begins to rise after6:00while the VOCS concentration is reducing. After8:00the photochemical reactions strength, the ozone concentration rises quickly while the VOCS concentration stays almost unchanged. Based on OZIPR MODE the EKMA curve shows that the ozone pollution in Nanjing is in the NOx-sensitive areas and affected little by the VOCs concentration, which verifies the previous observations.