Laboratory Study On Emission Characteristics Of PM_2.5 From Crop Residue Burning And Residential Coal Combustion In China

PM_2.5 is now very important atmospheric pollutant of concern,an it has significant effects on the environment,climate and human health.Crop residue burning and residential coal combustion are two of the major sources of PM_2.5 pollutant in China.This study selected three representative crop residues（wheat,corn and rice）and eight kinds of typical residential coals（bituminous coal/anthracite coal,chunk/briquette）in China.Laboratory measuremnts were conducted to get the characteristics of PM_2.5 from crop residue burning and residential coal combustion,including emission factors of OC,EC,water-soluble inorganic ions,element composition,PM_2.5-bound PAHs and source profiles of PM_2.5 and PAHs.Combined with the activity level data,this study set up the emission inventory of PM_2.5,and its harmful components from crop residue burning and residential coal combustion at the provincial level in China in 2012.There were no significant differences on PM_2.5 and total PAHs emissions from three typical crop residues burning.Measured emission factors of PM_2.5,OC and EC were 8.76±3.47g/kg,3.49±1.64g/kg and 0.31±0.12 g/kg.Emission factor of total PM_2.5-bound PAHs was 1.9±1.1 mg/kg.OC and EC are the most important part of PM_2.5,with the percentage content range of 36%⁴4% and 3%⁴%,respectively.Cl-and K+ are the most abundant content of water soluble inorganic ions,accounting for 5%⁸%,1%⁶% of PM_2.5,respectively.The composition profiles of PM_2.5-bound PAHs were dominated by PLT,PYR,BaA,CRH and BaP,mainly 4-6 ring,with the percentage of 11.9±3.5%,13.6±3.7%,15.4±2.5%,14.5±3.0% and 11.1±2.8% of total PM_2.5-bound PAHs,respectively.The OC/EC ratio was 10.91±3.06,and the K+/OC and K+/EC ratios were the range of 0.05⁰.18 and 0.71².29,respectively,which could used to identify sources of particles.There were significant differences on PM_2.5 and total PAHs emissions between residential bituminous coal and anthracite coal combustion.Measured emission factors of PM_2.5,OC and EC were 8.49±7.13g/kg,2.71±2.35g/kg and 3.78±4.00g/kg from bituminous coal（chunk）combustion,0.34±0.07g/kg,0.09±0.01g/kg and 0.01±0.00g/kg from anthracite coal（chunk）combustion,and 0.76±0.26g/kg,0.10±0.03g/kg and 0.02±0.01g/kg from anthracite coal（briquette）combustion.Emission factors of total PM_2.5-bound PAHs were the range of 142mg/kg³033mg/kg,0.41mg/kg and 0.98mg/kg¹.98mg/kg,respectively.OC and EC are the most important part of PM_2.5,with the percentage content range of 14.9%³3.0% and 3.45%³5.4%,respectively.SO42-was the most abundant content of water soluble inorganic ions,accounting for 4.9%²9.7%.The composition profiles of PM_2.5-bound PAHs were dominated by BbF and BaP,with the percentage of 17.4±4.9% and 18.6±2.8% of total PM_2.5-bound PAHs from bituminous coal（chunk）combustion,by PHE and ANT,with the percentage of 31.7±7.0% and 33.4±1.1% of total PM_2.5-bound PAHs from anthracite coal（chunk）combustion,and by CHR,with the percentage of 20.7±3.7% of total PM_2.5-bound PAHs from anthracite coal（briquette）combustion.Measured OC/EC ratios have a large variation,the values of bituminous coal（1.43±1.30）was significantly lower than that of anthracite coal（4.40⁶.63）,which should be pay more attention when using the ratio to do atmospheric particulate matter sources analysis.Based the self-measured EFs and activity level,we developed the emission inventory of PM_2.5,and its harmful components from crop residue burning and residential coal combustion at the provincial level in China in 2012.From our estimation,PM_2.5,OC,EC,HAPs,PAHs and BaPE were 886 kt,365kt,30 kt,513t,190 t and 26 t from crop residue open burning,1040 kt,428kt,36 kt,595t,224 t and 31 t from crop residue residential burning,588 kt,187kt,260 kt,815t,94478 t and 24013 t from residential coal combustion.The uncertainties of all kinds of pollutants in our emission inventory werer below 220%.Emission factors of PM_2.5 and its typical harmful components were measured from semi-coke residential combustion,which were significantly lower than the raw materials.Compared with the traditional clean coal anthracite coal（briquette）,dry semi-coke has better reduction effect.It could found obvious reductions in the total emissions of PM_2.5,and its typical harmful components by replacing the residential coals with semi-coke.