| The exposure to fine particles(PM2.5)in urban areas is considered a quite complicated where variety of residential,commercial and industrial sources are contributing the total PM2.5 concentrations and its associated chemical constituents.The study of residential indoor-outdoor atmospheric aerosols' levels attracted the attention recently.The purpose of this study is to examine the characteristics of PM2.5 and PM10 in indoor and outdoor microenvironments in cold region of China where winter heating and biomass burning are taking place,appoint the sources of particles by multiple methods,and then assess the influence of indoor and outdoor particles on human health.Investigation of PM2.5 and PM10 in ambient environment indicated that,the average mass levels of PM2.5 and PM10 during the entire study period were reported to be 82.4 ?g/m3 and 120.1?g/m3?annual averages?,with relative humidity?RH?and wind being the main factors affecting patterns of PM2.5 and PM10 distributions.Meanwhile,sum of major ions(NO3-,SO42-and NH4+),along with organic carbon?OC?were suggested to be the greatest contributors to the particles' mass levels.The results of source apportionment with PMF and UNMIX modeling suggested that,the major sources of ambient PM2.5 in Harbin city are: traffic?31%?,biomass burning?28%?,coal combustion?16%?,followed by secondary aerosols?11?,industrial processes?9?,and Ca-enriched source?5?.The huge amounts of PM2.5 and PM10 emitted from open fire biomass burning mainly happened in fall and early winter.The steady and continuous contribution from coal combustion to the particles mass levels during all the sampling periods is explained by a fact that,coal as a major source of energy is widely used for winter heating,industrial boilers and coal-fired power plants.According to LDA,the distribution patterns of PM2.5 and PM10 in winter heating period were distinct but overlapped for early winter before heating,and summer,suggesting that,PM2.5 and PM10 originated from different emission sources in winter heating period but from common/similar sources during summer and early winter before heating.This finding was confirmed by PMF results.As part of LDA,canonical discriminant function coefficients suggest that,species such as EC,OC,NO3-,SO42-,Cl-,Ti,Ca2+,Sr,Ba and Ni,are good predictors responsible of the dissimilarities in the particles mass levels between the three assigned sampling periods.Distribution patterns,associations among the inorganic constituents of the of PM2.5 and PM2.5 total mass levels and the interaction between indoor and outdoor PM2.5,were done using non-metric multidimensional scaling?NMDS?,and partial least square?PLS?regression.The results of those two methods indicated that,markers of coal combustion of the outdoor measured samples were overlapped with those of indoor measured samples during winter,while split up into two sub clusters during summer implying that some tracers of coal combustion particularly,Cr,Co,and Ni are also simultaneously emitted from industrial activities.In summer,PM2.5 subjected to more secondary aerosol formation compared to winter that indicated by the locations of NO3-,and SO42-on the two dimensions of the NMDS and PLS plots.In addition,NMDS and PLS have suggested also that,most of the inorganic contents of PM2.5 have showed stronger association between the indoor and outdoor.Enrichment factor?EFs?estimations supported results of source apportionment particularly the unique distribution pattern of manganese?Mn?,a typical tracer of metallurgical processes and the extremely high enrichment of cadmium?Cd?and chloride?Cl-?.The total concentrations of ?16 PAHs that classified by U.S environmental protection agency as priority pollutants,were very high,during colder months with mean values of 102±75.8 ng/m3,and 377±228 ng/m3 for the indoors and outdoors,respectively.The mean outdoor concentration of ?16 PAHs during winter reported to be 19 times higher than that of warmer months?summer and spring?,while the mean indoor level in winter was around 9 times and 10 times higher than indoor level for summer?mean 11.73±4 ng m-3?and indoor spring?mean 9.5±3.3 ng m-3?.During nighttime,the outdoor levels of PAHs revealed wider range of values as relative to datytime that was most likely related to outdoor temperature which revealed strong negative influence on ?16PAHs as compared to the low influence of relative humidity.Infiltration of PM2.5 from outdoor to indoor environment was estimated by regression analysis,I/O ratios and using Retene,Chrysene and Benzo[ghi]perylene were used as reference compounds,where the former two compounds were found to be a good estimators for calcualting infiltration factors?IFs?.It is estimated that 37%,44% and 68% of indoor measured PAHs were infiltrated from outdoor in winter,summer and spring respectively.The priority polycyclic aromatic hydrocarbons?PAHs?of indoor and outdoor PM2.5 suggested that,the main sources were coal combustion,crop residues burning,traffic,and unburned petroleum.LDA analysis revealed that the largest seasonal variations of PM2.5-bound PAHs were related to the high molecular weight congeners?HMW PAHs?.Potential cancer risk due to PAH exposure was evaluated through relative potency factor method?RPF?.High risk of cancer due to PAHs exposure during winter is suggested,where most of the carcinogenic potency was related to DahA and BaP,and to a group of congeners?Bb F,BkF,InP,and BaA?of high molecular weights.Generally,the cancer risk due to PAH exposure was two order of magnitude higher outdoors than indoors. |
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