Analysis Of Near-surface Ozone Formation Factors In Hangzhou Bay Area

As one of the key areas of China's economic development,the Yangtze River Delta region possess one quarter of China's economic and industrial value,which is an important engine for China's economic development.Hangzhou Bay area locat at the center of the Yangtze River Delta,whose particulate matter pollution and ozone pollution are becoming more and more serious as the economy developing.The particulate matter pollution has declined due to the national policies implementation,but the ozone problem has gradually increased.The relationship between O₃concentration and NO₂,CO and particulate matter concentration was discussed and the variation characteristics and laws of O₃ concentration in Hangzhou Bay area in northern Zhejiang?including Hangzhou,Huzhou,Jiaxing and Shaoxing?were analyzed in this paper.The causes of typical O₃ pollution processes in Hangzhou and Huzhou were analysed from the perspectives of meteorological factors and regional transmission.The results are diescribed as following.In 2017,the concentration of O₃ in Zhejiang Province showed the spatial distribution characteristics of“North High and South Low”.O₃ concentration is relative high in spring and summer,and is relative low in autumn and winter.And the Hangzhou Bay urban group in Zhejiang Province showed the most serious O₃pollution in Zhejiang Province.In 2017,the daily variation of O₃ concentration in Hangzhou Bay urban agglomeration showed a unimodal distribution.The peak concentration showed from 14:00 to 16:00.The peak of O₃ concentration appeared in May and July,and the concentration of O₃ in May was higher than that in July.The concentration of O₃ may be related to NO₂ concentration,temperature and relative humidity.In April and May,the O₃ concentration in the weekend was significantly higher than the O₃ concentration on the working day.In June and July,the O₃concentration in the weekend was lower than that in the working day.In August and September,the O₃ concentration in the weekend was slightly higher than that in the working day.The over-standard rate of ozone on the weekend was higher than that on the working day,which indicated that O₃ pollution was more likely to occur on weekends.The monthly average concentration of NO₂ is relative hihger in winter and spring and relative lower in summer and autumn,and showed an inverse phase relationship with O₃ concentration.The daily variation curve of NO₂ showed a bimodal distribution,indicating that the motor vehicle travel had a great impact on NO₂concentration changes in the morning and evening.The daily variation trend of CO and NO₂ are similar,indicating that the sources of CO and NO₂ are same and mainly derived from local emissions.However,CO is not involved into O₃ generation directly.The comprehensive analysis shows that the correlation between the concentration of CO and O₃ is not significant.The monthly mean concentration of particulate matter shows an inverse phase relationship with the monthly average concentration of O₃.But the daily average concentration of particulate matter is positively correlated with the daily average concentration of O₃ in summer,and negatively correlated in winter,indicating that O₃ and particulate matter combined atmosphere pollution are tend to occur in summer.There was a positive correlation between temperature and O₃ concentration in Hangzhou(correlation coefficient was 0.582^**,“^**”means double-sided 0.01 level significance test).The correlation between O₃ concentration and relative humidity was negative(correlation coefficient-0.481^**).The results indicated that the effect of temperature on the change in O₃ concentration is greater than that of the relative humidity.In the spring and summer,the concentration of O₃ in May and July exceed the standard seriously,and RH is lower than 70%for this period,indicating that the environment is prone to ozone pollution.There are two reasons for O₃ pollution analyzed fromthe O₃ pollution process in Hangzhou and Huzhou.The first reason is the Local photochemical reaction.The second reason is the regional transmission of pollutants.During the pollution period from May 25 to June 4,the pollutant air mass transmission in the east of Hangzhou led a great impact on the formation of the second pollution period?PE2?in Hangzhou and Huzhou.The external pollution source in Huzhou mainly comes from the northerly direction and the eastward direction.The contribution of pollution sources in the north is more obvious than that in eastward directioin.The results indicated that ozone pollution control not only needs to reduce local pollutant emissions but also need to strengthen regional joint defense alliance control.