| Fine particulate matter(PM2.5)is the most polluting compound in the atmospheric aerosols that harms the environment and human health.Organic aerosols are an important part of atmospheric aerosols,including polycyclic aromatic hydrocarbons,polychlorinated biphenyls and other chlorine-containing organic compounds.Hachang city group,which locates in northeast China,is the country's largest food base and an important old industrial base.In this study,four sampling points representing different pollution conditions in the Hachang urban agglomeration were selected.Organic carbon,elemental carbon,and organic molecular markers in the collected PM2.5 filter samples were analyzed.The main conclusions obtained are:?1?Mean PM2.5 concentrations at the four stations of Heilongjiang Meteorological Station?Site 1?,Harbin Meteorological Bureau?Site 2?,Changchun Beihai Park?Site 3?and Yushu Meteorological Bureau?Site 4?were?104.6±59.5??g·m-3,?93.8±39.9??g·m-3,?70.6±29.1??g·m-3 and?104.2±50.5??g·m-3,respectively.Sites 1 and 4 were mainly light and severely polluted,with pollution days of 11 d.Site 2 had 10 days of pollution,and the exceeding the standard reached 66.7%.Site 3 was dominated by good and lightly polluted weather with 6days of pollution.The OC/EC ratio results confirmed that the study area was greatly affected by emissions from coal combustion,biomass burning,and vehicle exhaust.?2?The non-polar organic compounds quantitatively identified in the PM2.5 samples mainly included n-alkanes,polycyclic aromatic hydrocarbons?PAHs?and hopanes.The carbon number distribution of the n-alkanes ranged from C17 to C36.The average CPI reflected the common influence of anthropogenic and biological sources on the distribution of n-alkanes,while%Wax Cn indicated that the contribution rate of higher plants is relatively low.The diagnostic ratios of PAHs confirmed the influence of coal combustion,biomass burning and traffic emissions.The isomerization index and normalized ratio of hopanes indicated that they were mainly derived from vehicle exhaust emissions,and coal emissions to somen extent.?3?The polar organic compounds quantitatively identified in the PM2.5 samples mainly included fatty acids,fatty alcohols,biomass burning tracers,sugars/sugar alcohols,secondary oxidation products,and biogenic/anthropogenic SOA tracers.The C18:1 concentration at the four stations was significantly higher than C18:2,indicating that the fatty acids in the study area mainly came from traffic sources.The low CPI index values of fatty alcohols(C15?C26)indicated that they have little to do with higher plant waxes and were dominated by anthropogenic sources.Levoglucosan was the most abundant among all compounds measured in this study.The high L/M ratio and G/M ratio indicated that the biomass burning materials were mainly hardwood and agriculture garbage.The high level of 2-methylglyceric acid confirmed that human activities area caused high concentrations of NOx?cis-pinonic acid+pinic acid?/3-hydroxyglutaric acid ratios indicated that the?-pinene-SOA were relative fresh.There was no significant correlation between DHOPA and levoglucosan during the entire sampling period,indicating that biomass combustion did not contribute much to the formation of DHOPA at these four sites,and more likely came from vehicle exhaust and coal combustion in winter.?4?Based on the EC-tracer method,the primary and secondary sources of SOA derived from the four sites accounted for 18.5%,19.9%,8.9%and 12.1%of the total OM,among which biomass burning was the main contributor,followed by isoprene-SOA tracer.The PMF model showed that emissions from coal combustion and biomass burning were the most important,accounting for 34.9%and 17.1%,respectively,followed by SOA from toluene?10.2%?,fungal spore-derived sources?9.5%?,diesel vehicle emissions?6.2%?,gasoline vehicle emissions?5.7%?,SOA from isoprene?5.1%?,SOA from?-pinene?3.9%?,plastic burning?3.6%?,the contribution of dust source was the smallest,only accounting for 3.3%. |
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