| With rapid economic and societal development,environmental problems are becoming increasingly severe,especially air pollution.Atmospheric particulates have attracted worldwide attention due to their significant impact on climate change,landscape visibility,and human health.Hefei,the provincial capital of Anhui,is a typical regional capital city,spanning an area of 11,445.1 km2 with a population of 7.965 million.This study on levels,chemical compositions,source identifications and pollution assessments of atmospheric particulate matter in Hefei City can be used as a reference by other cities.Based on the research literature and on-the-spot investigations,measurements of PM2.5,PM10,SO2,NO2,CO,O3 and AQI levels were collected from ten monitoring stations between December 2016 and December 2018,as well as 196 PM samples from four different sites between May 2014 and September 2018.XRF,XRD,IC,IRMS,SEM and TEM experiments were conducted.Furthermore,832 samples were collected for comparison between January 2014 and January 2016 in Tongling City.The research garnered the following results:(1)The average levels of PM10 and PM2.5 observed in Hefei exceeded both the WHO and national Chinese standards.PM2.5 and PM10 levels were lower in summer than in winter,and a bimodal distribution in diurnal variation was observed.Regarding spatial distribution,a decreasing trend was observed from north to south.PM2 5 and PM10 had strong correlation with NO2,CO and AQI.(2)The primary polluting element in Hefei was sulfur,and the observed concentrations of most elements were higher in winter than in summer.Elemental concentrations at the HF-A sampling site(which was more exposed to pollution generated by the road traaffic,construction,and industry)were more than double that of elemental concentrations observed at the HF-B sampling site.Furthermore,Hefei City had a lower proportion of pollutants and dual elements than that in Tongling City.(3)Regarding the compositions of atmospheric ions,the most ubiquitous water-soluble ions observed in Hefei were SO42-,NO3-and NH4+.The concentrations of Na+,Mg2+,Cl-,NO3-,SO42-and NH4+ were higher in winter than in summer.Concentrations of Ca2+and F-were close in winter and summer,and concentrations of K+was higher in summer than in winter.Sulfur and nitrogen oxidation rates were higher in winter than in summer.PM2.5 and PM10 had similar compositions and sources,although ions were more abundant in PM2.5.(4)The mineral compositions of atmospheric particles observed in Hefei City mainly comprised of quartz,plagioclase,calcite,pyrite,while the most common morphological structures were coal burning fly ash,soot,aggregate cement particles,mineral particles,flocculate-chain aggregate,etc.(5)Using the clustering analysis and principal component analysis,the primary sources of particulates were identified as marine salts,crustal components and anthropogenic sources.Regarding isotopic composition,the δ13C ratios of PM closely approximated to those of vehicle exhausts and coal burning emissions,while the δ34S ratios were close to those of coal,gasoline and diesel.(6)The enrichment factor method indicated that sulfur pollution in Hefei City was severe,with slight enrichment of elements such as zinc,nickel,copper and chromium.The potential ecological risk indexes of PM2.5 and PM10 in Hefei were high.Chromium in PM2.5 held a significant non-carcinogenic risk,while the carcinogenic risks of all the observed elements were slight. |
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