Study On The Mechanism Of SO₂/NO₂-O₃-VOC Synergistic Mineral Particles To Form Aerosols

Mineral particles are an important part of atmospheric particles.They can interact with inorganic-organic gases in the atmospheric environment and evolve mineral phases to affect the composition of atmospheric aerosols.Most of the previous studies on the formation mechanism of atmospheric aerosols focused on the formation of secondary pollutants such as sulfate,nitrate,and secondary organic aerosols in aerosols.Few studies have analyzed the relationship between the evolution of atmospheric mineral particles and the formation of atmospheric aerosols from the perspective of the evolution of atmospheric mineral particles.Therefore,based on the mineral particles,gaseous pollutants and meteorological conditions in the atmospheric environment of the Sichuan Basin（SCB）and the northern line of China,this study analyzed the source,mineral phase composition,migration path and evolution mechanism of mineral particles in the actual atmospheric environment.The heterogeneous mineral evolution experiments of atmospheric SO₂/NO₂-O₃-VOC（benzene,toluene,m-xylene,p-xylene）and atmospheric actual mineral phases（dolomite,calcite,mixed calcite-clinochlore）were carried out under different humidity and temperature conditions.The adsorption and electron transfer modes between SO₂/NO₂-O₃-VOC and dolomite（104）,calcite（104）,defective calcite（104）and Mg-doped calcite（104）were simulated.The mechanism of secondary aerosol formation and mineral phase evolution of atmospheric mineral particles was revealed.The main conclusions are as follows:（1）Quartz,gypsum,calcite,dolomite,albite,muscovite,kaolin,clinochlore,cordierite and other mineral phases exist in the urban atmosphere of the SCB and the northern region.Atmospheric mineral particles in the SCB mainly migrate from the north and northeast of the basin to the west and south of the basin.The northern region is affected by the northwest air mass in China,and the mineral particles mainly migrate from the northwest region to the east with the air mass.（2）The evolution of calcite and dolomite to gypsum occurs during the migration of atmospheric mineral particles in the cities of the SCB,and is affected by different sources of regional particles.In the southern part of the SCB,which is mainly affected by mineral dust,coal combustion and industrial sources,the process of synergizing calcite and inorganic gases to produce gypsum is the main process of aerosol formation in the region leading to air pollution.In the western part of the SCB,which is mainly affected by combustion sources,the synergistic effect of dolomite,inorganic gases and VOCs is the main process of aerosol formation in the region.There was a significant correlation between dolomite and m/p-xylene（R²=0.991,p<0.01）.In the migration process of atmospheric mineral particles in the northern line area,it was also found that the obvious transformation of carbonate mineral calcite to gypsum was mainly affected by the combustion source,and the carbonate mineral dolomite had significant correlation with benzene（R²=0.899,p<0.01）and toluene（R²=0.828,p<0.05）.（3）In the heterogeneous mineral evolution experiment of mineral particles and SO₂,it was found that SO₂ and dolomite formed rod-like gypsum in a watery environment and precipitated on the surface of dolomite.Calcite reacts with SO₂ to form columnar gypsum in a watery environment.In the reaction system of mixed calcite-clinochlore,columnar gypsum and rod-like S-containing minerals are formed,and minerals with similar morphology to dolomite on the surface of calcite appear.The simulation found that the O atom in SO₂ is easy to chemically adsorb the Ca atom on the dolomite（104）surface.It’s a hybrid of the 2p orbital of the O atom and the 3d orbital of the Ca atom to form a strong Ca-O bond.When SO₂interacts with calcite（104）,the interaction between O atoms in SO₂ and Ca atoms on calcite（104）surface is weaker than that on dolomite（104）,but there is a hybridization between the 2p orbital of O and the 3d orbital of Ca near the Fermi surface.