Chemical Characteristics, Component Spectrum And Secondary Generation Of Typical Indoor Emission PM_2.5

At present,PM_2.5 pollution has become one of the primary air pollutants in China.In modern society,people spend more than 80%of their time indoors.Indoor typical source emissions have caused widespread concern at home and abroad for indoor environmental pollution.In order to study the chemical characteristics of PM_2.5emitted by typical indoor sources?like Printing and burning of cigarettes?and contribute to indoor PM_2.5,we have used MinVol low-flow atmospheric particle sampler to collect PM_2.5 in outdoor?Environmental roof?,indoor?Graduate dormitory,print shop?and clean closed box with printing process and cigarette burning process,detecting the carbonaceous components and water-soluble inorganic ions in PM_2.5,analyzing the indoor and outdoor PM_2.5 pollution characteristics,source analysis and preliminary judgment of the impact of typical source emissions on indoor PM_2.5,and discharge PM_2.5 through typical emission sources in clean tanks.Through the study of the chemical characteristics of PM_2.5 emitted from the typical emission source in the clean box,to obtain the chemical composition spectrum and secondary generation of printing and cigarette burning.The main conclusions are reflected in the following three aspects:?1?Indoor and outdoor PM_2.5 mass concentration levels and chemical composition distribution characteristicsThe PM_2.5 pollution in outdoor environment is serious.The daily average value of outdoor PM_2.5 mass concentration exceeds the secondary standard of PM_2.5 daily average in the Ambient Air Quality Standard?GB3095-2012?.PM_2.5 pollution at the medium and high pollution level.The PM_2.5 pollution of indoor is also very serious.The PM_2.5 mass concentration in the daytime is higher than that in the nighttime.It is related to the smoking in the dormitory and the printing work pollution.The PM_2.5mass concentration at night outdooor is higher than that in the daytime,which is related to the large amount of particulate matter discharged during winter and the meteorological conditions are not conducive to the spread of pollutants;Carbonaceous components and water-soluble inorganic ions are the main components of indoor and outdoor PM_2.5;indoor typical source emissions contribute greatly to the carbon component of indoor PM_2.5;Indoor water-soluble inorganic ions mainly come from outdoor infiltration,and indoor pollution sources contribute less;The concentration of OC and EC in the night of the outdoor is higher than that in the daytime,which is related to the large amount of particulate matter discharged during winter and the unfavorable diffusion of meteorological conditions.?2?Source analysis of indoor and outdoor PM_2.5 and distribution characteristics of secondary componentsPM_2.5 in both indoor and outdoor,on daytime and nighttime has secondary organic carbon generation.The OC/EC value and WSOC/OC value in the print shop are higher than the outdoor,indicating the typical indoor emission source contributes to the secondary pollution in the room;the OC/EC value in the dormitory is much higher than the outdoor,but the WSOC/OC value is slightly higher than the outdoor,indicating that smoking is mainly a pollution to the indoors,and secondary pollution is not strong.The outdoor OC/EC value and WSOC/OC value are slightly higher than the nighttime,which is related to the high temperature between the daytime and the light radiation intensity is favorable for the photochemical reaction;the indoor OC/EC and WSOC/OC values are higher than the nighttime,indicating Printing and smoking sources contribute to secondary pollution in the room.The anion in the indoor and outdoor PM_2.5.5 is depleted.The PM_2.5 in the study area is alkaline;on the all the sampling points,the[NH₄⁺]/[SO₄^2-]values are bigger than 2,indicates that the sampling area is an ammonia-rich region.In the air,the secondary ion binding modes at daytime and nighttime are mainly?NH₄?₂SO₄,NH₄NO₃ and NH₄Cl,in the print shop nighttime secondary ion binding mode are?NH₄?₂SO₄ and NH₄NO₃.Judging from the carbon content distribution characteristics,the pollution sources of the outdoor are mainly coal and motor vehicle exhaust emissions,for the concentrations of OC₂,OC₃,OC₄ and EC₁ in the carbonaceous components are the highest,the pollution sources of the dormitory and printing shop is mainly biomass burning,and the concentration of OC₁ and OPC in the carbonaceous components are higher than those in the outdoor,which corresponds to the smoking activity in the dormitory and the print shop.?3?Analysis of typical indoor emission source printing and cigarette combustion emission characteristicsThe contribution of printing and cigarette burning process to indoor PM_2.5 is relatively high,which can explain the reason why the concentration of PM_2.5 in dormitory and printing shop is higher than that in outdoor;the contribution of cigarette burning to indoor source is larger than that of printing.The characteristic carbon component of the printing source is OC₁?OC₂?OC₃?EC₂ and the characteristic water-soluble inorganic ions are Cl^-?NO₃^-?Na⁺?NH₄⁺;the OC/EC characteristic values of different printers differ greatly,which may be different from the toner.Relevant,but the printing process of different models of printers is not polluted once,and the intensity of the secondary reaction after printing is relatively high,which is consistent with the conclusion of the actual printing shop;NH₄⁺,NO₃^-have two in the second stage?10-20h?after printing Secondary generation,may be the second stage?10-20h?after the end is nighttime,the temperature is lower,which is conducive to the formation of NO₃^-and NH₄⁺;SO₄^2-is mainly secondary generation,there is no SO₄^2-in the printing process,the first?0-9h?after printing and the second stage?10-20h?appeared and the proportion increased.The characteristic carbon component of the cigarette combustion source is OC₁,OC₃,and the characteristic water-soluble inorganic ions are NH₄⁺,Cl^-,NO₃^-,SO₄^2-,K⁺;Cigarette burning emits a high proportion of carbonaceous components in PM_2.5,which explains why the proportion of carbonaceous components in the quarters with smoking sources is significantly higher than that in the outdoor;The secondary formation of the carbon component after burning cigarettes is not obvious,but the OC/EC value is very high,indicating that the OC/EC characteristic value of the cigarette combustion source is high;NH₄⁺,NO₃^-have secondary generation in the second stage?10-20h?after Cigarette burning,which may be the second stage is nighttime,the temperature is lower,which is conducive to the formation of NO₃^-and NH₄⁺;During the analysis of the composition of the carbon component of PM_2.5secondary component,it was found that the carbonaceous component of WSOC in PM_2.5,whether indoors or outdoors,at night,or in a single typical source,is only OC₃.