The Characteristics Of Air Pollutant Emission From Catering Source And Its Influence On Atmospheric Environment In Lanzhou City

Accurately grasping and evaluating the emission characteristics,the spatial and temporal distribution of various pollution sources and their impact on the environment are of great significance for precise pollution control and fine management.In recent years,air pollutants emitted by catering sources have become one of the important factors affecting the environmental air quality of many cities.With the number of catering enterprises increasing year by year in Lanzhou City,more and more air pollutants are emitted from catering sources.Establishing the high-resolution catering source emission inventory in Lanzhou City and assessing its impact on ambient air quality can provide a scientific information for decision-makers to formulate control measures for catering sources,which will be conducive to continuously improve ambient air quality in Lanzhou City.Based on the survey results of catering industry,this study established the air pollution emission inventory of catering sources in Lanzhou City by using emission factor method and the material balance method.The number of restaurant enterprises in Lanzhou City is so large that it is difficult to spatially locate every restaurant enterprise.In order to solve this problem,coordinate correction method was used to locate large and medium restaurant enterprises and road location method was used to locate small restaurant enterprises.Based on this,the higher resolution emission inventory of catering sources in Lanzhou City with grids had been developed in this study.To identified the key compositions and species of VOCs in catering sources,maximum incremental reactivity?MIR?method and formation of aerosol coefficients?FAC?were used to estimate the potential formation of O₃?OFP?and the secondary organic aerosol formation potential?SOAFP?.In order to quantify the impacts of catering emission sources on the ambient air pollution in Lanzhou City,the WRF-Chem model was used to simulate the particulate mater?PM?contribution of catering sources emission to PM concentration in Lanzhou City in winter.The high-resolution emission inventory used in WRF-Chem for simulation was established by our research group.The main conclusions are as follows:1.In 2016,the total emissions of PM₁₀,PM_2.5,VOCs,OC,BC,CO,NO_x and SO₂ were calculated as 783.40 t,626.72 t,753.06 t,441.70 t,12.45 t,10590.28 t,281.55 t and 1443.37 t,respectively.From the spatial distribution of air pollutants emitted by catering emission sources,the emission amounts of PM₁₀,PM_2.5,VOCs,OC and BC were higher in Chengguan District,Qilihe District and Anning District.The emission amounts of CO and SO₂ were higher in Chengguan District,Yuzhong County,Yongdeng County.The emission amount of NO_x was higher in Chengguan District,Qilihe District and Yuzhong County.In terms of the emission sources of different catering scales,the small enterprises have the largest emission amounts of PM₁₀,PM_2.5,OC,BC,CO,NO_x,SO₂.The medium enterprises have the largest emission amounts of VOCs.2.From the components of VOCs,O-VOC has the largest proportion to the OFP,and aromatic hydrocarbons has the largest proportion to the SOAFP.The top 5species contributing to the OFP are ethylene,1-hexene,hexanal,acetaldehyde,acrolein.The top 5 contributing species to the SOAFP are 2,2,4-trimethylpentane,toluene,ethylbenzene,m/p-xylene and o-xylene.3.Simulation results showed that the PM concentration contributed by catering emissions was of the bimodal distribution.The two peak periods were located at11-14 hours and 18-21 hours,respectively.Moreover,the contribution of catering emissions to PM in the evening peak was higher than that at noon peak.At noon peak,the PM₁₀ and PM_2.5 concentrations were increased by catering emission sources with8.23?g/m³ and 5.93?g/m³ at the Lanyuan Hotel station,17.78?g/m³ and 12.80?g/m³ at the station of Railway Design Institute station increased,and 1.03?g/m³ and0.75?g/m³ at the station of Yuzhong Campus station.In the evening peak,the PM₁₀and PM_2.5 concentrations were increased with 16.14?g/m³ and 11.58?g/m³ at the Lanyuan Hotel station,34.02?g/m³ and 24.42?g/m³ at the Railway Design Institute station,and 2.10?g/m³ and 1.54?g/m³at the Yuzhong Campus station.In other periods,the contribution of catering emission sources on PM concentration at the three stations was little.The two valleys appeared at 10 hours and 17 hours,respectively.4.In winter,the prevailing wind direction in the urban area in Lanzhou City is north-northeast wind.The areas with high concentrations of PM₁₀ and PM_2.5contributed by catering emission sources are mainly located in Chengguan District and Qilihe District wehere is in the downwind direction.