A Study Of The Effect Of The Deterioration Of Diesel Trucks On VOCs Emission And Ozone Formation Potentials

As the main mode of land transportation in China,diesel trucks transportation account for 76.9% of cargo transportation,which is an important source of air pollution.When VOCs are emited into the atmosphere,it will have a photochemical reaction to form ozone.Relevant researches show that vehicle VOCs emissions are related to factors such as vehicle weight,emission standards,and accumulated mileage.Among them,deterioration factor,the VOCs emission factors continue to increase as the vehicle’s accumulated mileage increases,significantly affects the VOCs emissions.Studies have also shown that different species of VOCs have different ozone formation potentials.For the establishment of control policies for diesel trucks VOCs emission and ozone pollution,it is necessary to study the effect of the deterioration of diesel trucks on different species of VOCs emission and ozone formation potentials.In this paper,the diesel trucks were divided into 18 types according to vehicle weight,emission standards and accumulated mileages.Based on the method of chassis dynamometer,single photon ionization time-of-flight mass spectrometry and conventional five-component real-time analyzer,the emission concentrations of 50 kinds of VOCs from different types diesel trucks were measured and converted into VOCs emission factors based on mileages.Based on the calculation results,firstly,this paper analyzed the effect of different factors on diesel truck VOCs emissions,and recognized the VOCs components that had higher emission contribution.Secondly,the maximum incremental reactivity method was used to estimate the ozone formation potentials of different VOCs components of different diesel trucks.Then,this research established deterioration models for the emission factors of total VOCs and typical high-contribution VOCs.Finally,based on deterioration models,this study estimated the VOCs emission inventory of diesel trucks of China in 2018.This study showed that vehicle weight,emission standards,accumulated mileages had greater impacts on VOCs emissions,and different species of VOCs emission factors from various types of diesel trucks had obvious differences.The average emission factors for light,medium and heavy diesel trucks were 32.87 mg/km,67.97 mg/km and 216.67 mg/km.The average emission factors for diesel trucks under National Ⅲ and National Ⅳ standards were 185.69 mg/km and 63.19 mg/km.The average emission factors for accumulated mileages that less than 80 K km,between 80 K km and 161 K km,more than 161 K km were respectively 39.09 mg/km,85.51 mg/km and 276.45 mg/km.The VOCs emission factors under accelerated conditions were greater than those under other conditions.With the increase of speed,VOCs emission factors tended to decrease.The average emission factors of alkanes,aromatic hydrocarbons,olefins accounted for 43.06%,24.73%,18.57% of the total VOCs.Among them,aromatic hydrocarbons and olefins had higher atmospheric reactivity,with average OFPs respectively accounted for 29.98%,46.08% of the total OFPs.Pentene,1,3-butadiene,butene,xylene,methylcyclopentane and toluene were the key active components of VOCs in diesel trucks emission.The emission factors of total VOCs and typical VOCs increased exponentially with the increase of accumulated mileages.Based on the deterioration models,it is estimated that VOCs emissions were 463,900 tons,and typical VOCs emissions accounted for 48.16% of the total VOCs in China in 2018.