【作者】 王冠；

【导师】 陈发虎； 夏敦胜；

【作者基本信息】 兰州大学 ， 环境科学， 2008， 博士

【摘要】 城市街道尘埃是污染物质在城市环境中传播的重要介质,是室内灰尘污染物和城市大气颗粒物的主要来源,对城市土壤、水环境等生态系统和人体健康造成各种潜在的、直接的危害,是城市环境污染研究中的重要对象。兰州市是我国建国后首批重点建设的工业城市之一,工业污染源、生活污染源排放量大,加上特殊地理位置、地形条件和气象条件及不尽合理的工业布局、城市化、交通等多元化人类活动的综合影响,使兰州市大气污染问题尤为严重,成为国内外空气污染最严重的城市之一。本文选择兰州市城区为研究靶区,以街道尘埃作为研究载体,开展了大范围野外调查,采集了不同季节、不同功能区域内的178个街道尘埃样品,进行高分辨率的磁学、地球化学研究;对上述样品进行磁学、粒度、元素含量、有机质含量等一系列实验分析,利用地学统计软件（ArcGIS）对兰州市地区街道尘埃颗粒物的磁学特征、地球化学元素特征、粒度及有机质含量的时空分布特征进行了探讨,分析了城市街道尘埃的污染来源、主要污染物、污染特征等,同时结合数学统计软件（SPSS）分析了有机质含量及重金属污染的磁学响应特点,认识了解环境磁学参数与有机质含量、重金属含量之间的内在联系。主要获得如下认识:对研究区街道尘埃的粒度分析揭示了粒度的基本特征,发现兰州城市街道尘埃主要为粉砂和粉砂级以下（＜63μm）的颗粒,粒径分布主要表现为双峰和多峰非正态分布。风动力较大的区域平均粒径较粗,分选性较差;反之,在风动能小的区域,则主要以细颗粒物为主。空间分布特征表现为,东西部地区街道尘埃样品粒径较粗,中间地段相对较细。元素含量分析结果表明兰州市街道尘埃中主要含有Si、Al、Ca、Fe、Na、Mg、K、S、Ti、Cl、P、Mn和Ba等元素,前七种元素的平均含量占总含量的79.22%;其余元素含量相对较低。元素含量季节差异显著;冬季采暖期间燃煤量增加、兰州市特殊的地理特征以及冬季强逆温现象是造成污染元素含量升高的主要原因。街道尘埃中土壤来源的元素含量增加与春季的大风及沙尘暴天气有着密不可分的关系。空间分析结果表明,市区街道尘埃元素含量的空间分布差异较大,局部污染严重:城关区和西固区为燃煤污染严重区域,安宁区内污染相对较轻;在人口密集,车流量较大的城关区内交通污染相对严重;大型货运车辆造成的汽车尾气污染更为严重。西固区为未知来源元素Bi和Cs的高值区,初步推断它们主要来自工业污染。通过对研究区街道尘埃的有机质含量分析,揭示出兰州市街道尘埃有机质平均含量较高,季节和空间分布差异较大,冬季最高,春季次之,秋季最低;城关区、西固区、七里河区及安宁区内街道尘埃中有机质含量由高到低。上述结果表明,兰州市街道尘埃中的有机质组分除来自于土壤颗粒的贡献外,可能还来源于工业污染,汽车尾气以及人类日常生活所排放的各种污染物的贡献。环境磁学分析表明兰州市区内街道尘埃磁性矿物含量总体较高,主要磁性矿物是磁铁矿,并伴有少量的赤铁矿和顺磁性矿物;样品磁学性质主要受到亚铁磁性矿物和少量不完全反铁磁性矿物的控制;亚铁磁性矿物多为准单畴颗粒和多畴颗粒。与磁性矿物含量有关的磁参数(X_1f、SIRM、X_ARM、HIRM,SOFT及SOFT%)变化趋势相同,同时存在较大的季节差异,表现为冬春季磁性矿物含量明显高于秋季:而X_fd%、S-ratio、X_ARM/SIRM、SIRM/X_1f及X_ARM/X_1f等反映磁性矿物晶粒特征和类型的参数变化较小。空间分布上,工业区、密集街区以及交通要道等受到人为因素影响的区域,磁性矿物含量较高。一方面是由于兰州市特殊的地理位置、地形条件、气象条件使其区域内不同季节、不同样点街道尘埃中磁性矿物含量和粒度不同;另一方面,不尽合理的工业布局,人类活动对城市环境产生不同的影响,导致街道尘埃中的磁性矿物发生不同形式的迁移、转化、溶解,从而也影响了其磁性特征的变化。对磁参数的单元素方差（ANOVA）分析显示:众多磁学参数中,x_1f和SOFT%能够更有效的指示尘埃污染物磁性矿物含量的季节差异。通过磁参数与有机质含量的相关分析表明,六个主要反映磁性矿物浓度的磁性参数X_1f、SIRM、HIRM、SOFT、XARM和S_-20与有机质含量之间存在十分显著的正相关关系;而与其他磁性参数之间并不具有相关关系。与XARM的正相关性指示了单畴磁性颗粒对有机物质的贡献;同时与SIRM,HIRM及SOFT的显著相关表明了亚铁磁性颗粒物对街道尘埃中有机质的贡献。说明磁性参数可用作街道尘埃中有机质含量的代用指标。街道尘埃中砷（As）、铋（Bi）、铬（Cr）、铜（Cu）、锰（Mn）、镍（Ni）、铅（Pb）、钛（Ti）,锌（Zn）,铁（Fe）等10种重金属元素含量的分析结果显示,Bi和Cr两种重金属含量变化趋势相对一致,西部地区总体含量较高,东部地区逐渐降低,进一步证实其与工业活动关系密切;As、Cu、Pb及Zn四种重金属元素也表现出相同的变化趋势且变化波动较大,推断主要由道路交通环境的变化所引起;其余重金属元素（Mn、Ni、Ti、Fe）分别表现出不同的变化趋势。兰州市街道尘埃磁参数和重金属元素的相关分析结果显示,重金属元素（As、Cu、Mn、Ni、Pb、Zn、Fe）含量与反映磁性颗粒含量的磁性参数(X_1f)、SIRM、HIRM、SOFT、X_ARM)之间存在显著的正相关关系;比值参数（XARM/X1f,XARM/SIRM）与重金属含量之间的负相关关系反映了沉积物粒度组成对重金属含量的影响。Xfd%与Cu、Ni、Zn及Pb元素之间呈负相关关系,与其余重金属之间的相关关系不明显。S-ratio与Cu、Pb、Zn和Fe四种重金属元素呈正相关关系,但与其他重金属元素之间的相关关系不明显。表明街道尘埃中磁性组分与一些重金属元素相互依存,磁学参数可作为这些重金属分布变化的代用指标进行污染调查,用来指示工业生产导致的环境污染和监测道路交通的污染状况,追踪重金属污染变化趋势及其污染分布状况。研究表明,在获得大量实验数据的基础上,借助多元统计方法、地统计学技术与适量的地球化学分析,磁学参数的综合分析应用能够揭示街道尘埃污染分布状况,判别其污染来源,分析不同人类活动对环境的响应程度,有效地提取污染信息。此外,街道尘埃与其它载体相比,所记录的环境信息具有空间尺度较大,时间尺度相对较小的特点。因此,周期性地采集分析街道尘埃的环境磁学信息,能够灵敏地反映城市环境污染的变化特征。总之,该项研究显示,对街道尘埃进行系统的磁学、地球化学等研究,是在城市环境下开展大规模、高分辨率的、以磁学为主污染研究的一种经济、快速、有效的新方法,可以快速便捷经济地提供污染分布信息。更多还原

【Abstract】 Street dust,as an important medium of pollutants in the urban area,is an important source of house dust and urban atmospheric particulate matter.Street dust has received much attention due to its potential and direct risks to the ecosystem,such as soil and water system,and human health.Lanzhou is one of the key industrial cities after the founding of the nation.The severe air pollution problems of Lanzhou are not only caused by the large emission from industrial and domestic pollution sources,the special geographical position, topographical condition and meteorological condition,unreasonable industrial layout,and also affected by industry,agriculture,traffic and other multiplex human activities. Lanzhou has become one of the most seriously polluted cities in the world.Selecting street dust in Lanzhou as the research object,a total of 178 dust samples were collected in different functions regions of Lanzhou in different seasons by a large-scale field survey.The high-resolution magnetic and geochemical research were carried out,including magnetic measurements,grain size,element contents,organic matter content etc.,basing on the geosciences statistical software.（ArcGIS）,the temporal and spatial distributions of magnetic properties,geochemical elements（heavy metals）, grain size and organic matter content were discussed;the pollution sources,main pollutants and polluted characteristics of the urban street dust were analyzed as well.In addition,understand the relationship between the magnetic parameters and the organic matter content,heavy metals content were understood by the Mathematics and Statistics Software（SPSS）.The main conclusions are as follows:Through the research of the dust particle size analysis,basic characteristics of the particle size were revealed,we found that the main dust of Lanzhou city streets is sand or below silt sand level（＜63μm） of the particles,the size distribution was mainly double-peak and multi-peak normal distribution.With greater wind power,regional average size was coarser,and the sorting feature was poor;On the other hand,in the region with small wind energy,mainly fine particulate matter.The spatial distribution was characterized as below,dust samples with coarse particle size in the east and west streets, finer particle size in the middle streets.The results of element content analysis showed that street dust of Lanzhou City mainly contained Si,Al,Ca,Fe,Na,Mg,K,S,Ti,Cl,P,Mn and Ba etc.,the average content of the former seven elements accounted for 79.22%of total content,rest of the elements with relatively small percentage.The elements content had a significant difference in the season;the winter heating period with increased coal-fired,the special geographical features of Lanzhou City,as well as strong winter temperature inversion phenomenon were the two main factors which caused seasonal differences characteristics of.In the spring,the element content increment of the soil in the street dust has a close relationship,with the wind and dust storms.The spatial analysis results showed that the spatial distribution difference of the urban street dust elements was significant: Chengguan district and the Xigu district’s pollution are serious while Anning district is better.Xigu District is a high-value area of unknown-source elements,such as Bi and Cs, which were initially inferred from industrial pollution.Through analyzing the organic matter content of the street dust in the study area,it is revealed that Lanzhou street dust contained higher average levels of organic matter,with the distinct seasonal-spatial distribution difference,the highest value in winter and higher in spring,the lowest in autumn;the organic matter content was from high to low in Chengguan,Xigu,Qilihe and Anning district.The results showed that the organic matter of Lanzhou street dust may also come from industrial pollution,automobile exhaust emissions and a variety of pollutants from the daily life of human beings besides coming from soil particles.Magnetic measurements indicate a high concentration of magnetic minerals in Lanzhou street dust,the mainly magnetic minerals are magnetite with a small amount of hematite and magnetic minerals.The magnetic properties of samples were mainly controlled by the ferrimagnetic minerals and a small amount of incomplete antiferromagnetic minerals,ferrimagnetic minerals dominated by pseudo-single domain （PSD） magnetite and multi-domain particles（MD）.Magnetic parameters（Xlf,SIRM,XARM, HIRM,SOFT and SOFT%）,which were related to the concentration of magnetic materials is distinctly high in winter and spring,low in autumn.Similarly,higher concentrations associated with heavy industry,concentrated residential development,and vehicular traffic suggest mixed contributions of magnetic material from both anthropogenic and natural sources.However,the parameters which reflected the characteristics and types of the magnetic mineral grain,such as Xfd%,S-ratio,XARM/SIRM、SIRM/Xlf and XARM/Xlf.,got a small change.On the one hand,due to the special geographical location of Lanzhou,terrain,weather conditions,the content and particle size of the magnetic minerals were different in different season and sampling points;On the other hand,because of unreasonable industrial layout,the various impact of human activity on the urban environment,which led to different forms of migration, transformation,dissolution of magnetic minerals of the street dust,and the magnetic characteristics was also affected.The analysis of a single-element of variance（ANOVA） of magnetic parameters showed that:many magnetic parameters,X_lf and SOFT%are effective magnetic parameters that denote seasonal differences among magnetic properties in street dust,convenient and economical methods for monitoring street dust pollution.Through analyzing the correlationship of the magnetic parameters and the organic matter content,it is showed that six main magnetic parameters which reflected the magnetic mineral concentration,such as Xlf,SIRM,HIRM,SOFT,XARM and S_-20,had a very significant positive correlation with the content of organic matter,but no relation with other magnetic parameters.The positive correlation between XARM and oganic matter content indicated the contribution of single domain magnetic particles to organic matter; at the same time,the significant correlation with the SIRM,HIRM and SOFT has shown the contribution of ferimagnetic particles to the organic matters of street dust.Therefore, magnetic parameters can be used as substitutive indexes of organic matter content in street dust.The results of the heavy metal elements analysis,such as arsenic（As）,bismuth（Bi）, chromium（Cr）,copper（Cu）,manganese（Mn）,nickel（Ni）,Lead（Pb）,titanium（Ti）,zinc （Zn）,iron（Fe）,showed that Bi and Cr had a consistent change trend,the overall content level of the western region is relatively higher than the east,which is the further evidence of its relation with industrial activities;As,Cu,Pb Zn also showed the same trends and changed in a larger range,it is inferred that the change of the road communication condition induced this phenomenon,other heavy metal elements（Mn,Ni,Ti,Fe） had shown different trends separately.The correlation analysis of magnetic parameters and heavy metals of street dust showed that heavy metal elements（As,Cu,Mn,Ni,Pb,Zn,Fe） content had a significant positive correlation with the magnetic parameters（Xlf,SIRM,HIRM,SOFT,XARM）which reflected the magnetic particles content,The negative correlation between ratio parameters （XARM/Xlf,XARM/SIRM） and heavy metals content reflected the influence of the size composition of sediment on the heavy metal content.Xfd%had a negative correlation with Cu,Ni,Zn and Pb,but unconspicuous correlation with other heavy metals.S-ratio had a positive correlation with Cu,Pb,Zn and Fe,but inconspicuous correlation with other heavy metals.It indicates that the magnetic components of street dust are interdependent with some heavy metal elements,so magnetic parameters can be used as an index of these heavy metals to survey the pollution status,and monitor the industrial and traffic pollution. And it could be used to track the variation of the heavy metal and the distribution of pollutants.The research showed that the comprehensive analysis of the magnetic parameters can be used to reveal the distribution situation of the street dust pollution,determine the source of pollution,analyze the response extent of human activities and extract pollution information effectively basing on acquiring a large number of experimental and using multi-element statistical methods,geographical statistical techniques with the appropriate geochemical analysis.In addition,comparing with other study objects,street dust has the features of the large spatial scale and the smaller time scale in the environmental record. As a result,collecting and analyzing the environmental magnetic information of the street dust periodically can reflect sensitively changes features of the urban environment pollution.In short,the study showed that magnetic and geochemical analysis of the street dust, is a new,economic,rapid and effective method of carrying out large-scale,high-resolution and magnetic research under the urban environments,this new method can quickly,easily and economically provide the pollution information.更多还原