| By the end of 2020 year,the total mileage of highway in China has reached519.81 thousand kilometers,and the maintenance mileage has reached 514.40 thousand kilometers.Asphalt pavement is the most widely used pavement in China,which is usually accompanied by the release of VOCs(volatile organic compounds).The volume and development prospect of highway construction indicates that the construction process of asphalt pavement is one of the important emission sources of VOCs.However,due to the lack of VOCs emission standards in the process of road construction and operation,the unified evaluation methods and technical difficulties make the related research progress of VOCs emission and environmental impact of asphalt road materials in pavement construction process slow.By comparing the results of laboratory testing and field sampling,this paper proposes to use gas sampling bag / gas chromatography-mass spectrometry as the means of asphalt VOCs sample collection and analysis,and calibrate the content and composition distribution of asphalt VOCs with 102 photochemical reaction standard organic gases.The VOCs emission behavior in the process of typical asphalt pavement construction is quantified,and the characteristic component spectrum of asphalt VOCs under simulated actual working conditions is constructed.On this basis,the VOCs emission factor model of asphalt pavement is established,and the VOCs emission in the construction process of asphalt pavement is estimated.The environmental impact assessment index of asphalt VOCs emission is proposed,and the prioritity-controlled pollutant screening method is established,which provides theoretical support for the subsequent evaluation of asphalt VOCs emission reduction effect.Firstly,a VOCs generator for asphalt and its mixture is built in the laboratory to further study the influence of heating temperature,holding time,asphalt type and grading structure on asphalt VOCs emission and composition distribution.The main component is aliphatic hydrocarbon.It is found that most of the species are trace substances,in which the highest concentration of 10 substances account for about50% of the total content.Then,through field investigation and data collection,the actual emission characteristics of VOCs of typical asphalt pavement construction process are clarified,and the correlation between relevant results and laboratory simulated working conditions is verified.It is proposed to investige the composition and overall change trend of VOCs in the process as mixing,transpotation and paving by laboratory generating device,so as to solve the problems of unorganized emission,difficult collection and vulnerable to external environmental factors of on-site asphalt VOCs.According to the results of laboratory simulation,the asphalt VOCs emission factors are obtained as 0.24 g/t,0.62 g/t and 0.14 g/t,corresponding to mixing,transpotation and paving stage.Combined with the actual construction case,the total VOCs emission per unit area of asphalt pavement surface construction is calculated to be 0.470 g.The annual emission of asphalt VOCs from highway construction in China is estimated,and the distribution in different regions is analyzed.The potential hazards of asphalt VOCs to air pollution and human health are discussed,and the environmental load evaluation system is constructed from three aspects as ozone generation potential,secondary aerosol generation potential and health risk assessment.The priority-controlled pollutants are selected by using the information entropy method to solve the problems of complex composition of asphalt VOCs and difficult detection,so as to realize the targeted control.Finally,the asphalt inhibitor is introduced into the asphalt to quantify the emission reduction effect.When the amount of asphalt inhibitor is 0.5 %,the VOCs emission reduction efficiency can reach 35.08 %.Most of the priority-controlled pollutants are reduced without significant effect on the chemical structure and rheological properties of asphalt.This paper makes up for the blank of VOCs emission behavior and environmental assessment of asphalt pavement construction site,focuses on the potential harm of components to the atmospheric environment and human health,establishes the quantitative model of environmental impact assessment,and puts forward the screening of priority-controlled pollutants.It provides a scientific basis for the development of VOCs control and emission reduction strategy in the field of road engineering. |
