Study On Emission Factors Of PM_2.5-bound PAHs,OPAHs And NPAHs Produced By Rural Stationary Source Combustion

Polycyclic aromatic hydrocarbons and their derivatives are carcinogenic,teratogenic and mutagenic.During rural heating and cooking period,the burning of biomass fuels and coal will generate large amounts of PAHs and their derivatives.In order to study the emission factors from the burning of solid fuels such as biomass and coal during cooking and heating activities in rural areas in China,we use a self-designed combustion sampling device to study four kinds of coal fuels(clean coal:Lan coal and honeycomb coal;ordinary coal:Bituminous coal and loose coal),3 biomass pellet fuels(rectangular corn stalk pellets,cylindrical corn stalk pellets and peanut shell pellets),and 3 fuelwood fuels(pine,white pine and alder)in traditional stoves and gasifier stoves.PM2.5 samples were collected from the flue gas produced by the combustion of solid fuel.GC-MS was used to analyze 17 PAHs,6 OPAHs and 9 NPAHs in PM2.5 samples;OC/EC analyzer was used to analyze the concentration of OC and EC in PM2.5 samples;CO/CO2 two-in-one detector was used to analyze the CO and CO2 concentrations in the flue gas online.The emission factors of CO,CO2,OC,EC,PAHs,OPAHs and NPAHs were measured in this study.Through experimental analysis,we obtained emission factors for the combustion of 4 coal fuels,3 biomass pellet fuels,and 3 fuelwood fuels in traditional stoves and gasifiers stove in this study.In the two stoves,the emission factors of OC,EC,PAHs,OPAHs and NPAHs produced by the combustion of loose coal and bituminous coal are higher than that of Lan charcoal and honeycomb coal.The emission factors of PAHs and OPAHs produced by the three biomass pellet fuels are less than 3 fuelwood fuel.Compared with firewood,biomass pellet fuel has little effect on reducing NPAHs emissions.What’s more,in addition to the emission factor of OC produced by oak wood(OT)combustion,other emission factors of fuelwood combustion are higher than 3 biomass pellet fuels in traditional stove.The emission factors of EC produced by the fuelwood fuel and biomass pellet fuels are similar.We also measured the emission factors of 9 NPAHs produced by the combustion of 4 coals and 6 biomass fuels,including some undetected NPAHs.The emission factor of EC produced by Lan coal in gasifier is similar to that of traditional stoves.The emission factors of the OC and EC produced by the combustion of other three kinds of coal and 6 kinds of biomass pellet fuels in traditional stoves are significantly higher than the emission factors of OC and EC produced by combustion in a gasifier.The emission factors of EF∑UPAHs produced by the combustion of three fuelwood fuels and three biomass pellet fuels in a clean gasifier are significantly lower than in traditional stoves.The EF∑6OPAHs produced by the burning of cylindrical corn pellet and peanut shell pellet in a clean gasifier stove are lower than traditional stoves,but the EF∑6OPAHs produced by the burning of rectangular corn pellet are similar to traditional stoves.The emission factors of EF∑17PAHs and EF∑6OPAHs produced by the combustion of bituminous coal,loose coal,and Lan coal in gasifiers are significantly lower than that of traditional stoves,but EF:C17PAHs and EF∑6OPAHs produced by the combustion of honeycomb coal in gasifiers are higher than that of traditional stoves,which may be due to the internal structure of the gasifier is not conducive to the stacking of honeycomb coal,and it is not conducive to give full play to the honeycomb coal pores and air.In this study,the emission factors of NPAHs in the two stoves were similar.We discussed the molecular composition of PAHs and OPAHs in this study.The mainly PAHs produced by biomass pellet fuel combustion are PYR,FLT and PHE;the PAHs produced by coal combustion are rich in PYR,BaA and BbF.The main types of OPAHs produced by biomass and coal fuels are 9-FO and ATQ,and 9-FO and ATQ account for more than 70%and 60%of the total OPAHs produced by the combustion of coal and biomass fuels.In this study,there was a significant positive correlation between OPAHs and PAHs(P<0.05).The ratio of 7,12-BaAQ/BaA is significantly lower than that of 9-FO/FLU and ATQ/ANT.During the combustion of coal and biomass,OPAHs mainly come from the oxidation of polycyclic aromatic hydrocarbons.In addition to emission factors and molecular composition,we also measured the isomer ratios of PAHs produced by the combustion of 10 fuels in this study.Among them,the ratio of ANT/(ANT+PHE)produced by the combustion of 10 fuels are all greater than 0.1;the ratio of FLT/(FLT+PYR)produced by the combustion of coal and biomass fuel is greater than 0.5;The ratios of Ba A/(BaA+CHY)varies between 0.34 and 0.59;the ratio of BaP/(BaP+BghiP)varies between 0.55 and 0.74.Compared with loose coal,under the conditions of generating the same heat,the use of Lan coal can not only reduce the emissions of OC,EC,polycyclic aromatic hydrocarbons and their derivatives,but also achieve the purpose of saving coal resources.Compared with the two types of coal,peanut shell pellets can reduce the emissions of polycyclic aromatic hydrocarbons and their derivatives,but the consumption of peanut shell pellets is significantly higher than that of the two types of coal.In this study,it can be seen that the vigorous promotion of "gasifier stove+honeycomb coal" and "gasifier stove+Lan coal" in rural areas can effectively reduce the emissions of PAHs,OPAHs and NPAHs.Compared with untreated biomass fuels,vigorously promoting biomass pellet fuel can also effectively reduce the emissions of PAHs,OPAHs and NPAHs.