The Characteristics And Sources Of Ozone And VOCs Pollution In Shao Guan City During Summer And Autumn Typical Pollution Period

In the past two years,the overall air quality in Guangdong Province even all country has improved.However,ozone pollution is deteriorating.Shaoguan City,whose major air pollutant is ozone,ranks low in Guangdong Province in terms of air quality.As ozone pollution becomes more and more severe,it is extremely harmful to human health.Under this condition,it is significant to control ozone pollution.This paper analyzes the characteristics of ozone pollution in Shaoguan City from 2016 to 2018 and identifies the causes of ozone pollution.Online Preconcentration Gas Chromatography-Time of Flight Mass Spectrometer was used to continuously monitor VOCs from August 12 to September 18,2019,and analyzed the characteristics of VOCs pollution during ozone exceeding periods I and II（corresponding to before typhoon weather and before non-typhoon weather respectively）and non-ozone exceeding periods.Secondly,based on the positive definite matrix factor analysis model（PMF）,it is the first time to study the source of VOCs in Shaoguan City during the late summer and early autumn sub-ozone exceeding periods I and II and non-ozone exceeding periods.Finally,based on the Observational Base Model（OBM）,the reduction ratio of ozone precursors（VOCs and NO_x）corresponding to the ozone-generating precursors（VOCs and NO_x）before the typhoon and before non-typhoon weather in Shaoguan City is proposed,which could provide a reasonable and effective reference for reducing VOCs and ozone pollution control in Shaoguan City and other regions.The research results are listed as follows:First,by studying the influence of meteorology and precursors on ozone pollution,it was found that high temperature and moderately low relative humidity are conducive to ozone generation.The temperature is 33-39℃,especially when the temperature is 37-39℃,the ozone exceeds the standard severely,Whose exceeding rate is 5%.The relative humidity is35%-50%,especially when 40%-45%,the ozone exceeding the standard is the most serious,and the exceeding rate is 6%.Westerly winds dominate the distribution of high-concentration ozone,followed by northeasterly winds.Southerly winds dominate the distribution of high-concentration TVOC,followed by westerly winds.The south wind dominates the distribution of high-concentration NO₂.The ozone in the ozone exceeding period I,II are mainly controlled by VOCs,and their sensitivity to VOCs is weakened successively.Secondly,by analyzing the concentration,ozone generation potential（OFP）and relative incremental reaction activity（RIR）of each VOCs category and component during ozone exceeding periods I,II and non-ozone exceeding periods,the characteristics of photochemical pollution of VOCs in Shaoguan City are identified.The result shows that during ozone exceeding period I,Alkanes contribute the most to the concentration of VOCs,followed by Oxygenated Volatile Organic Compounds（OVOCs）,accounting for 40.9%and 30.0%,respectively..During ozone exceeding period II,OVOCs contributed the most to the concentration of VOCs,followed by alkanes,accounting for 38.4%and 36.8%respectively.The acetone concentration was the highest in the three periods,followed by propane.In the three periods,olefins were the key active component category of VOCs that contributed the most to OFP in Shaoguan City.The key VOCs components for ozone generation are propylene,isoprene,1-butene,acetone,toluene,isopentane,and isobutane.Ozone is most sensitive to changes in olefin concentration,The components sensitive to ozone in the three periods are isoprene,propylene,1-butene and acetone.Reducing these components is more effective in reducing ozone concentration.Finally,through the analysis of the sources of atmospheric VOCs and ozone control measures in Shaoguan City,it is found that the key pollution sources of VOCs and ozone in the ozone-excess period I are the use of liquefied petroleum gas（LPG）and the solvent usage source.The VOCs concentration accounted for 30.45%and 28.23%respectively.OFP accounted for 30.18%and 22.56%respectively.The key pollution sources of VOCs and ozone in the ozone-excess period I are the use of liquefied petroleum gas（LPG）and.the source of motor vehicle exhaust and oil and gas volatilization.The VOCs concentration accounted for 33.85%and 22.89%respectively.OFP accounted for 31.56%and 23.78%respectively.VOCs/NO_x shall be reduced at a ratio of 3:1 during ozone-excess period I,When is before typhoon weather;during the ozone-excess period II,When is before non-typhoon weather,VOCs/NO_x shall be reduced in accordance with 1:1-2:1 reduction;the 1:1 reduction of VOCs/NO_x during the non-ozone excess period shall be promoted.