Atmospheric Behavior Of Polycyclic Aromatic Hydrocarbons And Their Derivatives In The Urban Area Of Dalian

Polycyclic aromatic hydrocarbons（PAHs）are highly toxic organic pollutants,and short-term or long-term exposure to PAHs and their derivatives can bring adverse health effects to humans.In this paper,PAHs and their derivatives in PM₁₀ samples in different seasons and particulate matter classification samples in typical winter heating period in Dalian city were analyzed by using high-resolution gas chromatography-mass spectrometry.The pollution characteristics in the environment and distribution characteristics of which in different particle sizes of atmospheric particulate matter were studied,the main sources of PAHs were analyzed,and the health risks of respiratory exposure for the relevant pople were evaluated.The results of this study can provide basic data for environmental protection departments to formulate policies and regulations and air pollution prevention and control.The main conclusions are as follows:（1）The database（Datebase）of PAHs and their derivatives was established.Datebase mainly contains compound names,qualitative ion,quantitative ion and relative retention times,which can be used for qualitative and quantitative analysis of major PAHs and their derivatives in atmospheric particulate samples.（2）The concentrations of PAHs and their derivatives in PM₁₀ all had obvious seasonal changes,with the total concentration showing winter>autumn>spring>summer;The seasonal distribution characteristics of different categories of PAHs were consistent with that of the total concentration.Among them,the composition distribution of parent PAHs was high molecular weight PAHs>medium molecular weight PAHs>low molecular weight PAHs.（3）The concentrations of both PAHs and their derivatives in PM₁₀ showed negative correlations with ambient temperature.PM₁₀ and PM_2.5 were significantly negative correlation with atmospheric boundary layer height.The concentrations of PAHs and their derivatives in PM₁₀ were positively correlated with that of atmospheric SO₂ and NO₂ and negatively correlated with O₃ concentration.（4）The particle size distribution of atmospheric particulate matter concentration,and the total concentration of PAHs and their derivatives in the urban air of Dalian in winter showed a bimodal distribution,with two peaks located at 0.49～0.95μm and 7.2～10μm,respectively.（5）The main sources of PAHs and their derivatives in Dalian urban air were analyzed based on characteristic ratio method and principal component analysis.The main sources were the release from traffic roads and petroleum volatilization in spring and summer,and were from petroleum volatilization,coal or biomass combustion in autumn and winter.（6）The lifetime carcinogenic risk（ILCR）for adults was 1.28×10^-8 and for children was1.15×10^-8 during four seasons of the year.During winter heating period,7.2～10μm particulate matter entering the head airway mainly with a deposition efficiency of 0.87;3～7.2μm particulate matter entering the bronchial region mainly with a deposition efficiency of51.58;1.5～3μm,0.95～1.5μm,0.49～0.95μm and 0～0.49μm particulate matter mainly entered the alveolar region,with deposition efficiencies of 12.30,7.30,2.40 and 0.17,respectively,and the ILCR of adults was 8.81×10^-8 and the children was 6.46×10^-8.It can be seen that the ILCR values of residents in Dalian during all seasons and heating periods were lower than the safe and acceptable range of 1×10^-6 prescribed by the U.S.Environmental Protection Agency,indicating that there was no risk of cancer from PAHs for local residents breathing outdoor air.