| Volatile organic compounds(VOCs)including various alkanes,alkenes,aromatic hydrocarbons and their derivatives,etc.,exist in atmosphere ubiquitously in the form of steam at normal temperature.VOCs are generally emitted into the atmosphere by both natural(e.g.,emissions from trees)and anthropogenic sources(e.g.,vehicle exhaust,refineries,residential combustion,vehicular and industrial evaporation,and paints/solvent usage).Different kinds of VOCs will take secondary reaction during transportion in air after emission,and therefore,VOCs are important precursor to induce haze and photo-chemical smog.Accordingly it is of great significance to study the characteristics,chemical reactivity,sources and health risk assessment of VOCs.In summary,this study focused on the migration and transformation of VOCs in air of various types of cities in China.A series of 735 samples were sysmetically collected using an off-line sampling method(SUMMA canister)from 7 major cities in Anhui Province in southeastern China and determined by gas chromatography-mass spectrometer(GC-MS)to elucidate the seasonal variation and diurnal variation of VOCs,source apportionment and health risk assessment..The major findings of the present research work were as follows:(1)The concentration of volatile organic compounds(VOCs)such as alkanes,olefins,and aromatics in the atmosphere of Anhui Province were obtained.The annual concentration of VOCs in Anhui Province was 12.93 ppbv.It was found that the proportion of VOCs in the different cities was different:the concentration ratio of alkanes,aromatics and alkene was 52.4%,39.5%,and 8.1%respectively.(2)tThe spatial distribution variation of VOCs are revealed,following the order of Chuzhou>Hefei>Bengbu>Ma'anshan>Xuancheng>anqing>Bozhou.The concentration of VOCs is the highest in winter,the second in spring and autumn,and the lowest in summer.The diurnal variation is high in morning and evening,low in noon,which is basically consistent with the traffic flow in a whole day.(3)It was concluded that motor vehicle exhaust was the most important source in Bengbu,Maanshan and Xuancheng city,while industrial emissions was the most important source in Bozhou and Anqing,and solvent use was the most important source in Chuzhou and Hefei.In addition,plant sources were also found to be important sources of VOCs in Bozhou,Bengbu,Anqing and Chuzhou.(4)The chemical reactivity of VOCs from different cities in Anhui Province is clarified.The ozone generation potential(OFP)of atmospheric VOCs in Anhui Province ranged from 37.54 ppbv?58.49 ppbv in the atmosphere.It was found that aromatic hydrocarbons contributed the most to ozone formation(55%?64%),followed by alkanes(19%?29%),and alkenes(14%?19%).Isoprene and m/p-xylene were the two VOCs with the greatest potential contributing to ozone generation.(5)Effects of VOCs in the air of Anhui cities on human health are envaluated.The assessment found that for non-carcinogenic risks,the non-carcinogenic hazard quotient values of VOCs in the atmosphere of Anhui Province are within the safety value range recognized by the US EPA.For carcinogenic risks,benzene and other carcinogenic risk values exceed the limits given by the U.S.EPA,indicating that there would be a greater carcinogenic risk in the urban atmosphere of Anhui Province.It is s?ggested that relevant measures should be taken to reduce the impact of VOCs on residents' health and local eco-envionmental safety. |
PDF Full Text Request