Temperature Dependence Of Typical Escape VOCs Emission Characteristics And Its Impact On Ozone Pollution

In recent years,global climate change has become increasingly aggravated,with average annual temperature rising in most parts of China,frequent heat waves and frequent record highs of extreme temperatures.This will inevitably affect the emission characteristics of escaped Volatile anthropogenic Volatile Organic Compounds（VOCs）that are closely related to temperature and bring great challenges to ozone（O₃）control strategy.However,the impact of temperature on the emission characteristics of anthropogenic VOCs has not been considered in the existing emission inventories（EIs）,especially the anthropogenic escaped VOCs that are closely related to temperature.This will lead to the fact that the existing anthropogenic EI fail to accurately reflect the impact of temperature on the anthropogenic VOCs.Since regional high-resolution EI is the basis for the application of air quality models to simulate and predict the environmental behavior and pollution levels of pollutants,ignoring the impact of temperature on the characteristics of VOCs emissions will bring greater uncertainty to air quality simulations,particularly with O₃ simulation that closely related to meteorological conditions.Therefore,this paper combined many technical means of emission source monitoring,inventory establishment and model simulation.Two typical escaped volatile emission sources of vehicular evaporative emission and architectural paint VOCs emission were selected to carry out anthropogenic volatile emission experiments at different temperatures in this study.The impact of temperature on the emission characteristics of the two typical escaped VOCs was quantitatively identified,and the functional relationship between temperature and escaped VOCs emissions was established.Subsequently,the temperature was incorporated into the EIs system,and the dynamic temperature-driven EI（T-EI）was developed.Finally,a simulation study in the Pearl River Delta region（PRD）in September 2017 was carried out based on the WRF/SMOKE/CMAQ model system using this temperature-driven EI to identify the impact of the application of the T-EI on the O₃ concentration level and O₃ formation sensitivity in the PRD region.The main conclusions are as follows:（1）Temperature has significant influence on the emission characteristics of both vehicular evaporative emissions and architectural paint volatilizations.When the temperature was 313 K,the evaporative emissions of China V,China VI and E10 fuel was 25.7,12.3 and 26.7 times of that at 298 K.The volatilizations of water-based and solvent-based architectural paints was 6.5and 4.5 times that of 298 K.The emission of each VOCs category in typical escaped volatile source increased along with temperature,but with different degree.The weights of alkanes and alkenes increased with rising temperature,while the weights of aromatic hydrocarbons and oxygen-containing VOCs（OVOCs）decreased gradually.The weight of OVOCs volatile emissions in water-based coatings increased with rising temperature,while the weight of aromatic hydrocarbons decreased.In solvent-based coatings,the weight of alkenes and aromatics increased slowly with rising temperature.（2）According to the ideal gas law and the Clausius-Clapeyron equation,a thermodynamic model was constructed to describe the functional relationship between temperature and the emission of escaped VOCs.And then based on the measured data of temperature and evaporative emission of vehicular evaporative emissions and volatilizations of building paint.The functional relationship between temperature and emissions of the two typical escaped volatile sources VOCs was established.（3）Based on the emission source inventory of Guangdong Province in 2017,the temperature factor was incorporated into the EIs system to establish the temperature-driven VOCs dynamic emission source inventory.Under the condition of higher temperature,the escaped volatile source played a dominant role in the total anthropogenic VOCs EI,and had an obvious influence on the speciated VOCs.When the temperature increased from 298 K to 313K,the total emissions of these two typical escaped VOCs increased by about 7.4 times,and the proportion of anthropogenic VOCs increases from 19.3%to 66.7%,resulting in an increase of about 1.4 times of total VOCs emissions from anthropogenic sources.（4）The results of the O₃ simulation in September 2017 using the T-EI showed that the maximum O₃ concentration in the PRD region increased by 8.0μg/m³,while 12.0μg/m³ in Guangzhou,where VOCs control is relatively strong.Compared with the baseline inventory,the results of O₃ simulation using the T-EI were closer to the observation.The change in the O₃concentration level was more obvious in the VOCs-limited regions,especially at high temperature.The application of the T-EI would result in approximately 75.0%of the VOCs-limited areas in the PRD shifting to NO_x-limited,while 80.0%in Guangzhou.These findings highlight the importance of the development and application of the T-EI for O₃ control strategies on hot summer days,especially in the areas where O₃-precursor sensitivity dominated by VOC-limited.