Physicochemical Characteristic Of Fine Particulate Matter From Residential Coal Burning

Residential coal burning is one of the main sources of PM_2.5 pollutants in China.In order to obtain the emission characteristics of PM_2.5,this study selected 4 typical residential coals.And 102 samples were collected,84 samples were analyzed by a dilution sampling system.It provides the characteristics of pollutants discharged from residential coal burning and the chemical composition of fine atmospheric particles with the basic data.The contents of organic carbon?OC?and elemental carbon?EC?in the samples were measured by?TOR?,and the pollution characteristics of OC,EC were analyzed and discussed.The analysis process was carried out under the condition of pure He,and the filter membrane was heated for four times at the temperatures of 120??OC1?,250??OC2?,450??OC3?and 550??OC4?,respectively.After that,the temperature continued to rise from 550??EC1?,700??EC2?and 800??EC3?in three steps under the condition of containing 2%O₂.The results showed that bituminous coal emitted the highest proportion of total carbon in PM_2.5.And bituminous coal had a greater contribution to EC and OC in PM_2.5.The average value of 7 carbon components of each coal sample in the whole sample was calculated.Among the 7 carbon components,OC1accounted for the highest proportion of total carbon in bituminous coal.The result of OC2 showed:anthracite>briquette>bituminous coal.The result of OC3 showed:briquette>anthracite>bituminous coal;The result of OC4 showed:bituminous coal>briquette>anthracite;The result of OC4 showed:bituminous coal>anthracite;The EC2 in anthracite was greater than bituminous coal;EC3 was the highest in bituminous coal.The average values of TC/PM_2.5,OC/PM_2.5 and EC/PM_2.5 in bituminous coal combustion emissions of open fire were all higher than the average values of bituminous coal smoldering emissions.The average value of the mass fraction of 7carbon components in the open burning and smoldering stages of bituminous coal were analyzed,and the average percentage of the 7 carbon components in the total carbon in the open burning stage was EC1>OC3>OC4>OC2>EC3>EC2>OC1.The average percentage of the seven carbon components to the total carbon in the smoldering stage was EC1>OC3>OC2>OC4>EC2>EC3>OC1.The water-soluble inorganic ions were quantitatively analyzed by Dionex-600 type ion chromatograph,including SO₄^2-,NO₃^-,NH₄⁺,Cl^-,K⁺,Na⁺,Ca²⁺,F^-and Mg²⁺.The results showed that the percentage of water-soluble inorganic ions in PM_2.5 emitted by thecombustionofbituminouscoalshowed SO₄^2->Ca²⁺>Na⁺>Cl^->NO₃^->NH₄⁺>F^->K⁺>Mg²⁺;The percentage of water-soluble inorganic ions in PM_2.5 emitted by honeycomb coal combustion showed SO₄^2->Cl^->Na⁺>Ca²⁺>NH₄⁺>NO₃^->K⁺>F^->Mg²⁺;The percentage of water-soluble inorganic ions in PM_2.5 emitted by anthracite combustion showed SO₄^2->Cl^->NO₃^->Ca²⁺>Na⁺>NH₄⁺>F^->Mg²⁺>K⁺;The percentage of water-soluble inorganic ions inPM_2.5emittedbybriquettescombustionshowed SO₄^2->NO₃^->Cl^->Na⁺>Ca²⁺>F^->Mg²⁺>NH₄⁺>K⁺.In the stage of bituminous coal separation,except for the percentages of NO₃^-and SO₄^2-in the total water-soluble inorganic ions,the difference between smoldering and open-burning was large,and the percentages of other ions in the total water-soluble inorganic ions were not significantly different.In the stage of bituminous coal combustion,the percentages of NO₃^-and SO₄^2-in the total water-soluble inorganic ions were not significantly different from that of bright combustion,except that the percentages of NO₃^-and SO₄^2-in the total water-soluble inorganic ions were significantly different from that of bright combustion.In the bright burning stage,K⁺existed as chloride,NH₄⁺mainly existed as ammonium salt.In the smoldering stage,K⁺mainly existed as chloride and fluoride.The ratio of[NO₃^-]/[SO₄^2-]in PM_2.5 emissions from four different coal burning sources were all less than 1,and the relative levels of nitrogen oxides emitted by different coal-fired sources were:briquettes>Honeycomb coal>bituminous coal>anthracite.The relative contents of 19 inorganic elements in samples,Na,Mg,Al,K,Se,Sr,Cr,Mn,Fe,Co,Ni,Cu,Ga,As,Rb,Ag,Cs,Ba and Bi were tested by Inductively Coupled Plasma Mass Spectrometry?ICP-MS?.The results showed that during the whole sample collection process,the percentage of total inorganic elements in PM_2.5were briquettes>bituminous coal,briquettes>anthracite;in the stage of partial combustion,the percentage of total inorganic elements in PM_2.5 emitted by the open combustion of the six bituminous coal was greater than the percentage of inorganic elements in PM_2.5 emitted by the smoldering state.All samples were collected in the process,in terms of the percentage of 13 heavy metal elements such as Cr,Mn,Fe,Co,Ni,Cu,Ga,As,Cs,Rb,Ag,Ba and Bi in the total heavy metal emissions from residential coal combustion.The contents of Fe,As and Ba were higher in all the 11coal samples,while those of Ag,Cs,Bi and Co were lower,and the relative content of heavy metals was similar to that of bituminous coal.In terms of the percentage of Na,Mg,Al,K,Se and Sr in the total amount of other inorganic elements,the content of these six inorganic elements emitted by 11 kinds of residential coal combustion generally presented Na>Al>K>Mg>Se>Sr,and the relative content of other inorganic elements in the combustion stage of bituminous coal was similar.Among the characteristic ratios of some elements in PM_2.5 emission from residential coal burning,the range of ratios of Cu/Mn,Cu/Ni,Mg/K,Na/Al,Ga/Rb,Se/Sr and Ag/Cs were0.42-1.26,0.64-3.15,0.56-0.99,3.23-5.38,0.56-1.55,1.23-3.08 and 4.57-18.85,respectively.The ratio of Fe/As was between 1.34-2.74,except for the ratio of no.10coal which was 0.33.