| Studies have shown that mobile sources are an important source of air pollution in urban areas of China.Mobile sources are mainly divided into on-road mobile sources and non-road mobile sources,which have large amounts of volatile organic compounds?VOCs?emissions and complex components.VOCs is important precursors for the formation of ozone and fine particulate matter(PM2.5)pollution.It is urgent to conduct in-depth research on its VOCs emission characteristics and influencing factors to provide scientific support for the development of scientific and effective ozone and PM2.5 pollution prevention and control strategies.Studies on VOCs from light gasoline vehicle mostly focus on bench tests that use different test conditions to simulate actual vehicle emissions,but the real-time emission trend research of the local vehicle VOC under different conditions in the Pearl River Delta is lacking.Compared with motor vehicles,the study of VOC emission characteristics of non-road mobile sources is still in its infancy.Existing emission factor and source profile not only lack localized data,but also lack the measurement of oxygenated volatile organic compounds?OVOC?,which casued that the overall emission level of non-road source VOCs is seriously underestimated.To this end,this paper conducted an online bench test of 19 light gasoline vehicles,identified the real-time emission trends and characteristics of THC emissions from simulated urban areas under different conditions of light gasoline vehicles.This will provide a scientific basis for formulating refined control strategies for VOCs emissions from motor vehicles.The off-line sampling and analysis of the VOC profile of the typical construction machinery and inland ships in the Pearl River Delta region can fully describe the characteristics of VOC emissions from non-road mobile sources and estimate the emissions of non-road mobile sources more accurately.The conclusion of this study is as follows:Under the cold start conditions of light vehicles,the emission factors of Stage I to Stage?are 523.83,420.72,402.61,150.33,10.4,30.18±9.36 mg/km,and the emission factors of Stage I to Stage?under hot start conditions are 176.72 182.63,109.15,24.68,4.64,5.72±5.00 mg/km,the THC emissions of light-duty gasoline vehicles mainly occur in the first speed cycle,and the cold start emissions are significantly higher than the hot start.In the third speed cycle test,the cold and hot start The change trend of THC concentration with test speed is similar.Under simple transient conditions,the emission factors of vehicles from Stage?to Stage?are731.90±157.24,194.80±115.15,138.14±52.36 mg/km.OVOCs of Construction machinery and inland ships account for the main part of VOC emissions,for 46.9-76.5%.The emission proportion of each component of the three construction machinery is generally alkane?aromatic hydrocarbon??27?alkyne?27?alkene?27?OVOCs,and formaldehyde and acetaldehyde are the most OVOC species,which reflects the importance of including OVOC in the source profile measurement.The fuel-based emission factors for road rollers,graders and pile drivers are 3.12,3.12and 7.36 g/kg,and the emission factors for cargo ships and speedboats are 1.46±0.62and 0.44 g/kg.The source composition spectrum of inland ships is similar to that of construction machinery,which shows that the non-road mobile sources have similar VOCs composition characteristics due to the same fuel type and combustion method.Based on the emission factors obtained by the parametric bootstrap simulation method,the estimated VOCs emitted by construction machinery in Guangdong Province in 2017 were about 8851.0 tons,and the VOCs emitted by inland ships were about 4361.0 tons,equivalent to 47.8%and 23.6%of non-road mobile sources in 2012,which indicates that construction machinery and inland ships are the main sources of VOC emissions from non-road mobile sources. |
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