Methodological Improvement On Speciated Volatile Organic Compunds(VOCs)Emission Inventory And Reactivity Assessment

Haze and photochemical smog pollution are important environmental problems faced by many areas in the world.As the key precursor of ozone and secondary organic aerosols,the emission reduction of volatile organic compounds?VOCs?has become a research hotspot and focus.Speiated VOC reactivity-based control strateges are more effective than the total VOCs emission-based policies.However,the uncertainty of species-based VOCs emissions remains high.Therefore,this study aims at improving the quantitative method of species-based emissions.The high uncertainty may come three reasons,namely,the total VOCs emissions,the VOCs source profiles and the discripency of species in source profiles and total VOCs.Existing researches mainly aimed at reducing the uncertainty of total VOCs emissions.The influence of the last two resons remains unknow.In this study,taking on-road mobile source,one of the most contributed VOCs emission sources in China,as an example,we carried out a series of methodoligcal improvements to reduce the uncertainty of specieated VOCs emissions.We propose that the quantitative methods of regulatory pollutants should be applied to the quantification of speciated VOCs emissions.Since these methods have been used to quantify regulatory pollutants for a long time,their accuracy has been confirmed.However,considering the lackness of speciatd VOCs emission factors in the near future,we then made three improvements to the existing quantitative method of speciated VOCs emissions.First,motor vehicle emission standard-based VOCs source profiles were established to match the source classification of emission inventories.Then,species based-FID response coefficients?FRC?were introduced to unify the definition of VOCs in source profiles and total emissions.After that,unknow VOCs,defined as the difference between NMHC and the sum of spiceated VOCs corrected by the FID response coefficients.To assess these improvements,multi-instrument synchronous measurement was carried out,including LP-LIF for OH reaction rate mesurment,a series of on-line and off-line instruments for VOCs meurement and some on-line instruments for the measurement of exhaust flow,temperature,humidity,etc.The main conclusions are as follows:In 2015,exhaust emission of VOCs for on-road mobile source in China were 1.59 million tons and the ozone formation potentials?OFPs?were 6.56 million tons of O₃.Among them,formaldehyde was the most contributed VOCs specie,accounted for 17.18%and 37.37%of the total emissions and total OFPs,respectively.Light-duty gasoline passengers,motorcycles,light-duty diesel trucks and heavy-duty diesel trucks was the main contributor to VOCs emission and OFPs.The provinces with large quantity of light-duty vehicles,such as Guangdong Province and Shandong Province,are the areas with the highest contribution to the total VOCs emissions and OFPs.Compared with our improved speciated emission inventories?EIs?based on emission standard-based source profiles,OVOCs emissions were overestimates by the existing method based-EIs.When comparing with the EIs based on the source profiles with unknow species inserted and corrected by FRC,the existing method seriously underestimated the VOCs emissions of light-duty gasoline passenger cars of the IV and V national emission standard.Compared with the speiated VOCs in this study,the unknow species accounted 26.76%of diesel vehicle VOCs source profiles,17.16%for gasoline vehicles VOCs source profiles.Besides,we found that IVOCs and OVOCs are important components of VOCs emissions from on-road mobile sources in China,especially for diesel trucks,which account for 40%-90%.With the upgrading of emission standards,there are significant differences in the source profiles and emission factors of different types of vehicles.Last but not the least,by measuring the total OH reaction rate and calculating the OH reaction rate of the speciated VOCs and inorganic compounds,it is found that there are large reactivity missing of diesel truck emissions.For the V national emission standard heavy-duty truck,without considering the reactivity of NO,the missing reactivity accounted more than 60%of the total OH reactivity,indicate the OFP method based on the speciated VOCs reactivity probably misleading to the wrong control strateges.