Study On The Characteristics Of Tropospheric NO₂（Nitrogen Dioxide） Vertical Column Densities In Summer In Urumqi, Xinjiang, China

Nitrogen dioxide is a one of the main trace gases and plays an important role in the atmospheric chemistry. Its strong corrosive nature impact on human health if over inhalation. The densities of tropospheric NO2 has exceeded the grade nation discharge standard with the expansion of urban construction scale and increase in the number of motor vehicles. Ground-based measurements of the Multi Axis Differential Optical Absorption Spectroscopy(MAX-DOAS) have been carried out in Urumqi City since June 2013. In this study, we retrieved the tropospheric NO2 vertical column densities( VCD) over Urumqi from these MAX DOAS observations from June to August 2013. Main conclusions are as follows:(1)Over this period, the mean tropospheric NO2 VCD varied from 1.3 to11.5×1015molec·cm-2, with an average of 5.7×1015molec·cm-2, lower than the tropospheric NO2 VCD in summer of Beijing, Tianjin, Hebei, Chongqing and Guangzhou. There was a decreasing trend from north to south in tropospheric NO2 VCD at the time between 10 to 11 for farming area, industrial district and living area.(2)The tropospheric NO2 VCD has a space distribution in the five monitoring points and its order is Xinjiang University >San Daoba >Zhong Taihuaxue >Xinjiang Normal University >Wen Guang Campus. Over from the T-test Zhong Taihuaxue’s NO2 VCD has a insignificant differences with San Daoba and Xinjiang Normal University.Each monitoring points’ tropospheric NO2 VCD under different weather conditions shows that there has a insignificant difference at farming area,and has significant difference in other monitoring points. Tropospheric NO2 VCD’s order in different weather conditions is clear > cloudy > rainy. Under the same weather conditions tropospheric NO2 VCD’s difference shows that Zhong Taihuaxue’s NO2 VCD has a insignificant differences with San Daoba and Wen Guang Campus, and has a significant difference between other those monitoring points in clear day. And tropospheric NO2 VCD’s order is Xinjiang Normal University > Xinjiang University > San Daoba > Zhong Taihuaxue > Wen Guang Campus. There has a significant difference between other monitoring points except Zhong Taihuaxue and Wen Guang Campus has an insignificant difference,and tropospheric NO2 VCD’s order is San Daoba >Xinjiang Normal University >Zhong Taihuaxue > Wen Guang Campus in cloudy day. The tropospheric NO2 VCD of Zhong Taihuxue is higher than Xinjiang Normal University’s, and that there has a significant difference in rainy day.(3)The reasons of the differences in different functional areas and different weather conditions, the tropospheric NO2 VCD in summer in Urumqi caused by the Ribbon factors, terrain factors, the main pollutant factors and meteorological factors such as wind FET formation. Different functional areas of the source of tropospheric NO2 make different; Urumqi in the valleys, south than in the north, due to the thermal difference between the valley and its nearby air and cause daytime wind blowing from the valley slopes, forming a valley winds in the atmosphere troposphere to the south of the city NO2 accumulation, night wind blows from the hillside to form a mountain valley, tropospheric NO2 accumulation in northern urban areas; O3 concentrations increased in recent years, exacerbated by rising atmospheric concentrations of tropospheric NO2; summer, wind speed and sunshine duration are the main meteorological factors affecting tropospheric NO2 concentrations;divergent type summer urban wind farm is one of the reasons leading to higher concentrations of NO2 VCD in the north and south of downtown.