Chemical Characterization,Size Distribution,and Source Apportionment Of Ambient Particulate Matter In Tianjin,China

The ambient particulate matter(PM)pollution is very important due to its greater adverse impacts on the human health and natural environment.The chemical characterization,size distribution,and source apportionment of the ambient PM is important for determining the physiochemical properties and reflects the variability in local and regional PM emission sources and formation mechanisms.In this work,the daily PM1,PM2.5,and PM10 samples were collected during early summer 2018 at a sub-urban site in the urban-industrial port city of Tianjin,China.The collected PM1,PM2.5,and PM10 samples were analyzed for the carbonaceous,ionic,elemental,and specific sugar species.The size-wise PM's average mass concentrations were 32.4,53.3,and 102.6 ?g/m3 for the PM1,PM2.5,and PM10,respectively.The PM1 constituted 63%of the PM2.5 and 33%of the PM10,and the PM2.5 constituted 53%of the PM10,on average.The fraction-wise PM's average mass concentrations were 32.4,20.9,and 49.3 ?g/m3 for the PM1,PM1-2.5,and PM2.5-10,respectively.The coarser PM2.5-10 fraction constituted most of the PM10(47%),followed by the finer PM1 fraction(33%)and the intermodal PM1-2.5 fraction(20%).The OC,EC,NO3-,and SO42-were the dominant chemical species in all the PM sizes,while the NH4+was dominant in the PM1 and PM2.5 sizes and the Si was dominant in the PM10 size.The finer PM1's major chemical species were the OC,SO42-,NO3-,EC,NH4+,Ca2+,S,and Si,the intermodal PM1-2.5's major chemical species were the NO3-,SO42-,Si,NH4+,S,and OC,and the coarser PM2.5-10's major chemical species were the Si,NO3-,OC,Ca,Ca2+,Fe,Al,and SO42-.The higher OC and EC indicated the dominant combustion contributions,the higher NO3-,SO42-and NH4+ indicated the dominant secondary particles contributions,and the higher Si,Ca,Al,and Fe indicated the dominant mineral dust contributions.The chemical characterization of the ambient PM was based on the mass concentrations,chemical compositions,and important characteristic ratios for both the size-wise PM and the fraction-wise PM.The characteristic ratios of PM1/PM2.5,PM1/PM10,PM2.5/PM10,PM1/PM10,PM1-2.5/PM10,PM2.5-10/PM10,OC/EC,SOC/OC,OM/TCA,AE/CE,NO3-/SO42-,NH4+/SO42-,K+/EC,levoglucosan/K+,V/Cu,and V/Ni were employed to investigate the chemical characteristics of the ambient PM.In this work,the size distribution and characteristics of the carbonaceous,ionic,elemental,and specific sugar species were categorically investigated for the fraction-wise PM during 2018 early summer in Tianjin,China.The carbonaceous and ionic species exhibited the bimodal distribution and were distributed mostly to the finer fraction,whereas the elemental species exhibited the unimodal distribution and were distributed mostly to the coarser fraction.The specific sugar species indicated the significant contributions of the biomass burning and primary biogenic sources.The bimodal levoglucosan distribution indicated the significant biomass burning contributions to the finer and coarser fractions.The unimodal glucose,fructose,and arabitol distribution and the bimodal mannitol distribution indicated the dominant primary biogenic contributions to the coarser fraction.The anthropogenic sources(combustion processes,traffic emissions,secondary particles,etc)contributed mostly to the finer PM1 and intermodal PM1-2.5 fractions,whereas the natural sources(primary biogenic,marine salt,mineral dust,etc)contributed mostly to the coarser PM2.5-10 fractionIn present work,the Positive Matrix Factorization(PMF)model was employed for the PM1,PM2.5,and PM10 source apportionment.The PM1 and PM2.5 source apportionment by the PMF model indicated the main sources of secondary aerosols(25%and 34%),biomass burning(17%and 20%),traffic emission(20%and 14%),and coal combustion(17%and 14%).The PM10 source apportionment by the PMF model revealed the main sources of secondary aerosols(21%),biomass burning(18%),mineral dust(18%),and traffic emission(14%).The biomass burning factor involved the agricultural fertilization and waste incineration.The anthropogenic sources(secondary aerosols,combustion processes,traffic emission,etc)contributed more to the PM1 and PM2.5,while the natural sources(mineral dust,marine salt,primary biogenic,etc)contributed more to the PM10.The biomass burning sources contributed significantly to all the PM sizes,while the primary biogenic sources were more evident in the larger PM10 size.The biomass burning and primary biogenic contributions were ascertained by the specific sugar species.The 3-day biomass burning peak period and 2-day high,moderate,and low biomass burning periods were determined based on the levoglucosan concentrations,and were confirmed and supported by the NASA's fire spots maps,NOAA's HYSPLIT backward trajectories,and biomass burning factor's contributions.The 3-day primary biogenic,mineral dust,and shipping emissions peak periods were determined based on the primary biogenic indicators(glucose,fructose,arabitol,and mannitol),mineral dust indicators(Al,Fe,and Si),and shipping emissions indicators(V/Cu and V/Ni),and were confirmed and supported by the relevant factors' contributions and NOAA's HYSPLIT backward trajectories.This research work significantly contributes to the chemical characterization,size distribution,and source apportionment studies of the ambient PM in the near-port cities influenced by the diverse sources.The main anthropogenic sources of the secondary particles,combustion processes,and traffic emissions contributed more to the PM1 and PM2.5,while the main natural sources of the mineral dust,marine salt,and primary biogenic were more evident in the PM10.The anthropogenic sources(combustion processes,secondary particles,traffic emissions,and industrial activities)contributed mostly to the finer PM1 and intermodal PM1-2.5 fractions,whereas the natural sources(mineral dust,marine salt,primary biogenic,and mechanical processes)were more evident in the coarser PM2.5-10 fraction.The specific sugar species' inclusion is important in the ambient PM's chemical characterization,size distribution,and source apportionment studies to provide the valuable information regarding the biomass burning and primary biogenic contributions.The fine particles(particularly PM1)have a deeper reach and more toxic constituents,leading to more serious adverse impacts on the natural environment and human health.Therefore,the finer particles particularly the PM1 needs more focus in the future research studies and should be considered together with the PM2.5 and PM10 for the national standards and health guidelines.