Distribution Characteristics And Influencing Factors Of Near-surface Ozone Concentration In Hefei

Air pollution becomes an increasing concern in China recently due to its impact on human health and the economy.Most important characteristic of the air pollution in China is the complex polluted gases under high aerosol loadings.The dataset of the ozone concentration and aerosol optical properties as well as the ambient meteorological condition is combined used.The dataset acquired in Hefei city and Xingtai city in 2016 is be used to compare the location difference of the ozone pattern.The dataset acquired form 2003-2004 is analyzed to understand the historical change of the ozone concentration in Hefei city.Meanwhile,the simultaneous aerosol optical parameters and corresponding meteorological characteristics were also investigated to explain the patterns of the ozone distribution.The main new findings are as follows:1,Near-ground ozone concentration has strong seasonal variation in Hefei city.The highest ozone concentration is found in summer,followed by spring,and the lowest in winter.But the aerosol concentration is high in winter and spring.And at different sites,the composition of the ozone precursor is also different.For example,in the urban,it is mainly composed by automobile exhaust and industrial gases,while in vegetative covered area the ozone precursor mainly comprising of plant-derived organic matter.The peak concentration of ozone in the near-surface atmosphere in the city is found at 4:00,15:00,and 20:00 varying three peaks,bimodal,and single-peak pattern.Aerosol concentration in the daytime is characterized by lower in the morning higher in the evening.The concentration of nitrogen oxides is generally shows peaks in the morning and evening.2,low temperature,high relative humidity,low wind speed weather conditions are favorable to particulate matter formation.Observations have found that particulate matter formation may be promoted when the wind speed is greater than a certain threshold.There was a positive correlation between near-surface ozone concentration and solar radiation,temperature,and wind speed,the meteorological factors will dominant in different seasons.There was a high correlation between ozone concentration and temperature in summer,and wind speed in winter.When south or east wind is prevailed in the SKYNET Hefei super site,the high ozone concentration is easy to accumulate,while under the north wind,the ozone concentration is often lower.Local photochemistry in summer is the main way to generate ozone gas,according to conventional meteorological factors to predict the trend of ozone generation.3,During the Chinese Spring Festival the pollution of the fireworks and transportation are more serious,resulting in local emission is more significant and complex.The concentration of aerosols and ozone is higher,but the duration lasts a short time,during which the aerosol impact on the formation of ozone is not obvious.