Emission Of Volatile Organic Compounds (VOCs) From Light-duty Vehicles In The Pearl River Delta Region

In the Pearl River delta region,the average annual concentrations of SO₂,NO₂ and PM₁₀had continued to decline over the past decade,while the levels of VOCs and O₃ in the region had been rising and fluctuating.Whatever primary and secondary pollution prevention and control,O₃ and its key precursor VOCs need to be paid enough attention.Road mobile source is the biggest contributor to VOCs emission in cities of the Pearl River delta region.In addition,with the continuous and steady increase of vehicle ownership in this region,the influence of VOCs on vehicle emissions becomes more important.According to the sensitivity analysis,on-road vehicle is the primary source of uncertainty.However,the existing emission factor and source profiles are not only lack of localized data,but also lack of OVOCs component data,which may lead to a serious underestimate of OVOCs.In addition,in the study of dynamic inventory,dynamic activity data of motor vehicles is relatively easy to obtain,but source profiles and source emission factor are in great demand.By means of more precise and localized VOCs testing of emission sources,the influence brought by differences in vehicle driving conditions and their own attributes can be identified,which will provide a scientific basis for formulating refined control strategies for vehicle VOCs emission.In this paper,the existing vehicles in the Pearl River delta region are selected as the main China III to state VI vehicles.We set the VOCs test system,obtained the exhaust flow rate and concentration of VOCs emissions data,from the gasoline and diesel in the bench and real driving emission.Then these data is calculated and analysed for the VOCs emission factor and component spectrum which is influenced by different areas,vehicles,working condition.After obtaining the refined VOCs source source profiles of motor vehicles,the reactivity of source spectrum was calculated and the potential of ozone generation?OFP?of motor vehicles under different working conditions was evaluated.Then,the on-line mass spectrometer was used to test the high-resolution source profiles based on velocity,and the real-time emission of each component was analyzed.Finally,the cold-and hot-start in the bench test were executed.The real-time TOG emissions were analyzed and the TOG total amount was corrected.Finally,the carbon closure equation was constructed to calculate the missing amountLight gasoline vehicles emit more C₅^C₇ alkanes and OVOCs but less alkenes when driving at a uniform speed of 25 km·h^-1,and the alkanes in exhaust gas source profiles are the highest,followed by aromatic hydrocarbons and OVOCs,alkynes and halogenated hydrocarbons were least.The main components of VOCs in exhaust gas are C₅^C₇ alkanes,benzenes,aldehydes and ketones,etc.The exhaust VOCs emission factors of light-duty gasoline China III,IV and V vehicles are 50.12±46.83,40.86±31.15 and 3.25±0.65 mg/km,respectively.The light diesel vehicle was tested on the real road in the city.The emission of diesel vehicles in the four speed conditions is mainly OVOCs,followed by aromatic hydrocarbon.As the speed increases,the number of all VOCs groups decrease.As for OVOCs,formaldehyde and acetaldehyde emissions were higher,but higher formic acid was detected in driving.The cold-/hot-start+ECE×3 test was carried for light-duty gasoline,diesel and oil electricity-blended vehicle.First,real-time THC emission after cold-or hot-start was analyzed by FID,and then NMOG was calculated based on mileage and fuel consumption,emissions factors of total VOCs at cold-,hot-start+ECE×3 were 88.35±67.58 and 75.94±99.38 mg/km,0.68±0.46 and 0.71±0.85 mg/g fuel.Finally,the carbon closed equation was constructed with the corrected NMOG,and it was found that the proportion of carbon loss would increase with the increase of total NMOG emissions.