The Evolution Characteristics Of Speciated VOCs Emissions In The Pearl River Delta And Its Impact On The Formation Potential Of Secondary Pollution

Haze and photochemical smog pollution are urgent atmospheric environmental problem in the Pearl River Delta(PRD)at this stage.Volatile organic compounds(VOCs),as important precursors of ozone and secondary organic aerosols,are the key to continuous improvement of air quality.Wide sources and complex species structures are the main characteristics of VOCs,and the reactivity of each species is significantly different,so speiated VOC reactivity-based control strateges are more effective.In recent years,the national and local governments have made great efforts to formulate a series of policies ranging from the total VOCs emission-based policies to the speiated VOC reactivity-based control.However,VOCs emissions in the PRD are still rising,indicating that there are still large uncertainties in the current speciated VOCs emission trend.For example,the emission factor and source profiles do not consider interannual changes,and OVOCs are seriously underestimated.Tends in the 2006-2017 speciated VOCs emission was quantified and analyzed in this study by constructing dynamic emission factors and source profiles methods.And by exploring the impact of species emission evolution on OFP and SOAP,the key species and their main drivers were identified.This study also provided important implications for reactivity-based control strategies.The results showed that during the period 2006-2017 in the PRD:(1)The VOCs emission factors of most vehicles and industries have been decreasing continuously under the control measures,and their source profiles had obvious evolution characteristics of a decrease in the proportion of aromatic hydrocarbons and an increase in OVOCs.(2)The VOCs emissions increased steadily during 2006–2014 and then decreased after2014.Alkanes(on-road mobile sources were the main contributor)and OVOCs(solvent use sources were the main contributor)emissions decreased by 11% and increased by 12%,respectively.(3)Exploring the impact of VOCs emissions on the formation potential of secondary pollution,we found that the trend of OFP and SOAP are more consistent with the changes in emissions.Decline in OFP and SOAP was mainly driven by aromatic hydrocarbons and alkanes contributed by on-road mobile sources after 2014.Toluene,m/p-xylene and formaldehyde were the key species identified in this study by combining emissions and reactivity.(4)The proportions of domestic and foreign controlled species in emissions,OFP and SOAP were compared,we found that the current VOCs emissions lack precise control,and the one-size-fits-all key control species are not suitable for all emission sources.Therefore,the key species of refined source classification need to be proposed.The annual dynamic VOCs emission factors and source profiles methods constructed in this study can improve the accuracy of the speciated VOCs emission,and provide scientific data support for studying the formation potential of secondary pollution and achieving longterm precision contorl.