The continuous measurement of nitric oxide (NO), nitrogen dioxide (NO 2) , nitrogen oxides (NO x ) and ozone (O 3 ) was conducted in Tianjin from September 8 to October 15, 2006. The data were used to investigate the relationship between the O 3 distribution and its association with ambient concentrations of NO, NO 2 and NO x (NO and NO 2 ). The measured concentrations of the pollutants in the study area varied as a function of time, while peaks in NO, NO 2 and O 3 all occurred in succession in the daytime. The diurnal cycle of ground-level ozone concentration showed a mid-day peak and lower nighttime concentrations. Furthermore, an inverse relationship was found between O 3 NO, NO 2 and NO x . In addition, a linear relationship between NO 2 and NO x , as well as NO and NO x , and a polynomial relationship between O 3 and NO 2 /NO was found.The variation in the level of oxidant (O 3 and NO 2 ) with NO 2 was also obtained. It can be seen that OX concentration at a given location is made up of two parts: one independent and the other dependent on NO 2 concentration. The independent part can be considered as a regional contribution and is about 20 ppb in Tianjin.An obvious difference in NO, NO x and O 3 concentrations between weekdays and weekends was also found, but this difference did not appear in NO 2 .Lastly, the diurnal variation of O 3 concentration under different meteorological conditions was demonstrated and analyzed.
Meteorological and aerosol data were measured at the atmospheric boundary layer observation station in Tianjin, China, and were analyzed to study the effects of aerosol mass, composition, and size distributions on visibility and short-wave radiation flux. The results show that fine particles played important roles in controlling visibility in Tianjin. The major contributors to light extinction coefficients included sulfate (28.7%), particulate organic matter (27.6%), elemental carbon (19.2%), and nitrate (6.1%). In addition to the measurement of aerosol composition, the size distribution of aerosol number concentrations were also measured and classified between haze days and non-haze days during spring. The extinction characteristics of ambient aerosol in haze days and non-haze days were calculated using Mie theory model. The average extinction coefficient and scattering coefficient of atmospheric aerosols were 0.253 1/km and 0.213 1/km in non-haze days, while 0.767 1/km and 0.665 1/km in haze days. A radiation transmission model LOWTRAN7 is also applied in this study. The model calculated radiant flux densities in haze days and non-haze days, which showed a fairly agreement with the observation results, showing that the heavy aerosol loadings in Tianjin had significantly impact on atmospheric visibility and radiation fluxes.
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