Study On The On-road Emission Characteristics Of Regulated Gases And VOCs From Typical Vehicles In Zhengzhou

Recently,with the social and economic development,car ownership of China has continued to grow at a high speed.While cars bring convenience to people’s lives,they also put great pressure on the atmospheric environment.In this study,the portable on-board measurement system(PEMS)was used to test the on-road emissions from four categories of vehicles in Zhengzhou.CO,HC and NOx were monitor in real time;the volatile organic compounds(VOCs)were sampled by Suma canisters and analyzed by gas chromatograph-mass spectroscopy(GC-MS)detector.Based on the results,firstly,the impacts of road conditions and emission standards on emission factors of regulated pollutants were analyzed,and the relationship between pollutant emission rate and vehicle specific power(VSP)was explored.Then the influence of road conditions and emission standards on VOCs emissions was explored and further their ozone formation potential(OFP)were evaluated with maximum incremental reactivity(MIR)method.Finally,based on the on-board test results,the amounts of pollutant emitted by light vehicles in Zhengzhou in 2017 were estimated.The conclusions are as follows:(1)Improving road conditions and tightening emission standards can effectively reduce the emission of regulated pollutants.When the vehicle is driving on urban roads,due to the low speed,frequent acceleration and deceleration,and frequent start and stop,resulting in insufficient fuel combustion,the emission factors of CO,HC and NOx are higher than the suburban roads and highway roads;the improvement of emission standards can effectively improve vehicle emissions.Compared with China III vehicles,the emission factors of various pollutants of China V vehicles have been reduced by 50.4-82.1%.(2)When VSP <0,the pollutant emission is low,and VSP has little effect on the pollutant emission;the vehicle is at idle or stable during Bin 0(-1 k W/t <VSP≤1 k W/t),so the pollutant emission rate is the lowest;aggressive driving conditions or high VSP under heavy load will cause high emissions of motor vehicles.(3)Exhaust VOCs are mainly aromatics and alkanes,which together account for 68.1-98.0% of the total VOCs emissions;long-chain alkanes(such as dodecane,n-undecane,n-decane)and aromatic hydrocarbons(such as naphthalene)are the main components of VOCs emitted by diesel vehicle;and the content of short-chain hydrocarbons(such as isopentane,acetone and propane)in LDGV and LPGB exhaust is higher.(4)Road conditions have significant impacts on the emission factors of VOCs,but not on VOCs composition.Tightening the emission standards can effectively reduce the emissions of VOCs from diesel vehicles.Although the composions of the VOCs form different standards are different,in general,the compositions of VOCs followed the sequence of alkanes > aromatic > alkens > carbonyls > halohydrocarbon > other compounds.(5)The OFP of heavy-duty diesel vehicles is much higher than that of other vehicles,and the reducation of diesel vehicle VOCs is of great significance to the control of ozone generated by vehicles;aromatic hydrocarbons are the main contributors of exhaust OFP,accounting for 49.6-93.4% of the total OFP.(6)In 2017,the emissions of CO,HC,NOx and VOCs of light vehicles in Zhengzhou were 22862.4 t、2452.4 t、4067.0 t and1143.5 t,respectively.Gasoline vehicles are the main contributors to CO,HC and VOCs of light-duty vehicles,and account for 93.8%,89.3% and 90.7% of the total emissions,respectively;NOx is mainly emitted by diesel vehicles,accounting for 74.3% of the total emissions.