青藏高原背景站大气VOCs浓度变化特征及来源分析

采用大气预浓缩与气象色谱/质谱联用法,对2013-09-13到2013-10-14期间在国家大气背景站青海门源站所采集的大气样品进行分析.结果显示,本次研究共检测出38种挥发性有机物(VOCs),其中烷烃16种,烯烃11种,芳香烃9种,卤代烃2种.从组成成分来看,烷烃所占比例最大,达58.6%,烯烃和芳香烃分别占29%和10.5%,卤代烃所占比例最小,仅为1.7%.观测期间大多数VOCs物种呈现白天浓度低、夜晚浓度高的变化趋势,具有明显的高原站点特性,但异戊烷、异戊二烯、甲苯则呈现相反趋势.采用臭氧生成潜势(OFP)对VOCs各组分活性进行分析,各类VOCs中烯烃对OFP贡献最大.利用主成分分析VOCs物种,提取出4个因子,分别归类于燃烧源、天然气和液化石油气的泄露、工业源、生物源.结合HYSPLIT 4.0后向轨迹模型,进一步确定气团的来源与运输途径,发现来自南向的污染源贡献是门源地区VOCs物种浓度增加的主要原因.

Characteristics and sources analysis of atmospheric volatile organic compounds in the Tibetan Plateau

The concentrations of volatile organic compounds were monitored from 13^th September 2013 to 14^th October 2013 at Menyuan, a national background monitoring site in the Tibetan plateau. Total 38 VOC species were detected, with 16 alkanes, 11 olefins, 9 aromatics, and 2 halogenated hydrocarbons. Alkanes were the most abundant, followed by olefin, aromatics and halogenated hydrocarbons. They accounted for 58.6%, 29%, 10.5% and 1.7% of the total VOCs, respectively. Most VOCs exhibited diurnal variation of higher in nighttime and lower in daytime, with isoprene, i-pentane and toluene the only exceptions. By calculating ozone formation potential (OFP) of various VOCs, olefins made the biggest contribution. We further analysed the sources of VOCs by the method of Principal Component Analysis (PCA) and HYSPLIT 4.0 backward trajectory, and confirmed that the pollutants from south and southeast of Menyuan site have significant effects on the increase of VOCs concentration.