兰州市大气降尘中的多环芳烃特征及其与地形和气候因素之间的关系

Characters of PAHs in Dust Deposition and Their Relationships to the Topography and Climatic Factors in Lanzhou

兰州的石油化工产业以及燃煤排放的污染物中含有较多的多环芳烃 ,而兰州市特殊的狭长河谷盆地地理环境 ,污染物很难通过自然扩散消除 ,尤其是冬季的污染更加严重。本文通过对兰州市大气降尘在地表沉积样品的分析 ,了解兰州市多环芳烃的主要成分 ,以及与地理特征和气候因素之间的关系。在兰州市区及郊区共采七个地表土样 ,用气相色谱法分析测定土样中的多环芳烃 ,其中乙基芘在兰州市广泛分布 ,而在西固石油化工炼制区和阿干镇煤矿区有较多的甲基硫芴、甲基苯并硫芴 ;在城关区东岗镇、兴隆山旅游区的PAHs化合物则表现出明显的差异性 ,氧芴、萘、萤蒽等系列化合物占主要。由于在城关区和七里河区之间的兴隆山、白塔山形成一狭口地形 ,西风或西北风使西固石油化工炼制区产生的污染物从兴隆山后山的阿干镇山谷带走 ,从而减少了对城关区的污染。

Contaminants discharged by petrochemicals industry and coal-burning in Lanzhou contain much Polycyclic Aromatic Hydrocarbons (PAHs), but they are hardly eliminated by natural diffuse process because of special geographic environment of a narrow and long river valley basin which makes the pollution more serious especially in winter. In this paper, it is understood the relationships among main components of PAHs, geographic distributing character and likely meteorologic influencing factors by analyzing samples of the earth's surface sediment of dust deposition in Lanzhou. Seven soil samples were sampled from different locations in Lanzhou and its suburb. Gas chromatography was used to detect PAHs in these samples. Ethyl perylene distribution is abroad in Lanzhou. There were more methyl dobenzothiophene and methyl benzodobenzothiophene in Xigu petrochemical-refine district and Agan town's colliery district, but there were distinct differences in Chengguan District Donggang town and Xinglong Hill's tourism district, in which dibenzofuran, naphthalene and flouranthene were more dominant. The Xinglong Hill and Baita Hill between Chengguan District and Qilihe District form a narrow-opened landform, west wind or northwest wind bringed contaminations discharged by Xigu petrochemical-refine district away through Agan District valley behind Xinglong Hill which else alleviated Chengguan District's pollution.