宝鸡市街尘、土壤及渭河沉积物重金属污染研究

【作者】 王利军；

【导师】 卢新卫；

【作者基本信息】 陕西师范大学 ， 环境科学， 2008， 硕士

【摘要】 城市灰尘、城市土壤以及河流沉积物是城市生态环境系统的重要组成部分。研究资料表明,城市化迅速发展的过程中,受城市工业、交通、商业和建筑业等的影响,城市灰尘、城市土壤、城市水体以及河流沉积物重金属污染严重。而宝鸡有关这方面的研究鲜见报道。为了弄清楚宝鸡地区的环境现状,本文以宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物为研究对象,首次对宝鸡市街尘、土壤以及渭河沉积物三种环境介质的理化性质,重金属元素的含量、分布、来源、存在形态以及迁移转化等环境地球化学问题进行了较为系统的研究,取得了以下结论与认识:1.利用pH计、马弗炉、磁化率仪、激光粒度仪和X-Ray荧光光谱仪（XRF）研究了宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物的pH值、烧失量（LOI）、低频磁化率（LF）、高频磁化率（HF）、频率磁化率（FD）、机械组成以及常量组分等理化性质。分析结果显示,宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物的pH值分别是8.983,8.482,8.639,均呈碱性:烧失量（LOI）分别是8.77%,5.20%,2.47%,城市街尘可能受到了一定的有机污染;低频磁化率（LF）和高频磁化率（HF）在城市街尘中的水平明显高于城市土壤和河流沉积物,在城市土壤和河流沉积物中基本一致,而频率磁化率（FD）在城市土壤当中明显高于城市街尘和河流沉积物,在城市街尘和河流沉积物中基本一致;城市街尘和城市土壤的机械组成主要是粉粒（街尘:71.300%;土壤:59.066%）,河流沉积物的机械组成主要是粉粒和沙砾（粉粒:45.610%;沙砾:41.467%）;常量组分在三种环境介质当中差异不十分明显,含量水平基本一致。2.利用XRF、电感耦合等离子体质谱仪（ICP-MS）和原子荧光分光光度计（AFS）分析了宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物中重金属元素（Cu、Pb、Zn、Mn、Fe、Co、Ni、Cr、Cd、As和Hg）的含量水平。分析结果表明,城市街尘中Cu,Pb,Zn,Mn,Fe（以Fe₂O₃的百分含量表示）,Co,Ni,Cr,Cd,As和Hg的平均含量分别是123.2μg/g,408.4μg/g,715.1μg/g,804.2μg/g,7.22%,15.9μg/g,48.8μg/g,126.7μg/g,6.60μg/g,28.3μg/g和1.112μg/g;城市土壤中的平均含量分别是35.4μg/g,36.7μg/g,102.4μg/g,708.6μg/g,4.90%,19.0μg/g,32.7μg/g,89.3μg/g,0.50μg/g,13.4μg/g和0.282μg/g;河流沉积物中的平均含量分别是24.2μg/g,22.7μg/g,68.3μg/g,534.8μg/g,3.85%,15.1μg/g,25.6μg/g,90.9μg/g,0.41μg/g,9.7μg/g和0.470μg/g。同中国土壤元素背景值比较显示,城市街尘中重金属的污染比较严重,尤其是Cd、Hg、Pb、Zn和Cu,其分别是中国土壤元素背景值的68.0,17.1.15.7,9.6和5.4倍;而城市土壤和河流沉积物中重金属元素的含量水平与中国土壤元素背景值基本一致,除了Cd和Hg。同国内外其它城市（街尘和土壤）和其它河流（沉积物）比较显示,宝鸡城市街尘中重金属元索的含量高于国内外大多数城市;而城市土壤和河流沉积物则处于中等水平。相关分析和聚类分析显示,宝鸡城市街尘中Pb、Zn和Mn主要来源于现代城市的工业、商业和交通运输等人为活动:Cd、Hg、Fe、Co、Ni、As、Cu和Cr主要是自然来源。3.利用相关分析研究了宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物中重金属元素同理化指标之间的关系。分析结果表明,在宝鸡城市街尘中,低频磁化率、高频磁化率和频率磁化率同大多数重金属元素之间显著相关,但黏粒、粉粒和沙砾同重金属元素之间不存在相关关系;而在宝鸡城市土壤和渭河宝鸡段河流沉积物中恰恰相反,且常量组分在宝鸡城市土壤和渭河宝鸡段河流沉积物中同大多数重金属元素之间也显著相关。利用物理筛分的方法,结合XRF分析主要研究了宝鸡城市土壤和渭河宝鸡段河流沉积物中重金属元素（Cu、Pb、Zn、Mn、Fe、Co、Ni、Cr和As）在不同粒径范围的分布情况。结果表明,在宝鸡城市土壤和渭河宝鸡段河流沉积物中,重金属元素在不同粒径范围的分布差异不十分明显。4.采用修正的欧共体BCR四步连续提取技术,利用ICP-MS和电感耦合等离子体光谱仪（ICP-AES）研究了宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物中重金属元素（Cu、Pb、Zn、Mn、Fe、Co、Ni、Cr和Cd）的存在形式和迁移转化特征。结果表明,在宝鸡城市街尘中,重金属元素随环境条件发生迁移转化的顺序是:Cd（90.11%）＞Pb（82.33%）＞Zn（79.32%）＞Cu（62.35%）＞Mn（51.48%）＞Co（29.02%）＞Ni（23.62%）＞Cr（18.68%）＞Fe（10.21%）;在宝鸡城市土壤中,重金属元素发生迁移转化的顺序是:Pb（68.75%）＞Cd（63.93%）＞Co（59.25%）＞Mn（57.32%）＞Zn（29.01%）＞Cu（25.94%）＞Ni（20.70%）＞Cr（15.36%）＞Fe（7.30%）;在渭河宝鸡段河流沉积物,重金属元素发生迁移转化的顺序是:Mn（56.70%）≈Pb（56.65%）＞Cd（53.66%）＞Co（48.82%）＞Cu（43.99%）＞Zn（21.93%）＞Ni（15.49%）＞Cr（11.43%）＞Fe（9.62%）。相比较而言。城市街尘具有更大的潜在危害。5.采用M（u|¨）ller地累积污染指数和Lars Hakanson潜在生态风险指数评价了宝鸡城市街尘、城市土壤以及渭河宝鸡段河流沉积物中重金属的污染现状。结果表明,宝鸡城市街尘主要受Cd、Hg、Pb、Zn等重金属污染;宝鸡城市土壤和渭河宝鸡段河流沉积物主要受Hg和Cd污染;相比较而言,城市街尘重金属污染比较严重。更多还原

【Abstract】 Urban dusts, urban soils, and river sediments are important parts of ecologically environmental system of city. Researches show that the heavy metal pollution of urban dusts, urban soils, urban water, and river sediments affected by industry, traffic, commerce, and construction of city is very heavy during the fast development of urbanization. However, the few researches related to Baiji in this field are reported.In order to clarify the environmental status of Baoji City, the paper chooses urban street dust and urban soil of Baoji City and river sediment of Baoji section in Weihe River as object researched, firstly researches the physical and chemical property and the content, distribution, origin, speciation, and mobility of heavy metal elements systematically, and attains the following results and cognitions:1. The physical-chemical property, including pH, Loss on Ignition （LOI）, low frequency susceptibility （LF）, high frequency susceptibility （HF）, frequency-depended susceptibility （FD）, physical formation, and the contents of constant elements, of urban street dust and urban soil of Baoji and river sediment of Baoji section in Weihe River is researched by means of pH-meter, Muffle, Susceptibility-meter, Laser Size Meter, and X-Ray Fluorescence Spectrometer （XRF）. The analytical results show that the pH values of urban street dust, urban soil, and river sediment are respectively 8.983, 8.482, and 8.639 and are all alkaline; that the LOI are respectively 8.77%, 5.20%, and 2.47% and urban street dust has probably some organic pollution; that LF and HF in urban street dust are higher than urban soil and river sediment and the two later are basically same, while FD in urban soil is higher than urban street dust and river sediment and the two later are basically same; that urban street dust and urban soil of Baoji is dominated by silt （street dust: 71.300%, soil: 59.066%） and river sediment of Baoji section in Weihe River is dominated by silt and sand （silt: 45.610%, sand: 41.467%）; that the diferences of constant elements in three environmental factors are not quite clear and their contents are basically same.2. The concentrations of heavy metal elements （Cu, Pb, Zn, Mn, Fe, Co, Ni, Cr, Cd, As, and Hg） of urban street dust and urban soil of Baoji and river sediment of Baoji section in Weihe River, are analyzed through XRF, Inductively Coupled Plasma Mass Spectrometer （ICP-MS）, and Atomic Fluorescence Spectrometer （AFS）. The analytical results show that in urban street dust, the mean contents of heavy metal elements （Cu, Pb, Zn, Mn, Fe-Fe₂O₃%, Co, Ni, Cr, Cd, As, and Hg） are respectively 123.2μg/g, 408.4μg/g, 715.1μg/g, 804.2μg/g, 7.22%, 15.9μg/g, 48.8μg/g, 126.7μg/g, 6.60μg/g, 28.3μg/g and 1.112μg/g; that in urban soil. the mean contents are respectively 35.4μg/g, 36.7μg/g, 102.4μg/g, 708.6μg/g, 4.90%, 19.0μg/g, 32.7μg/g, 89.3μg/g, 0.50μg/g, 13.4μg/g and 0.282μg/g; that in river sediment, the mean contents are respectively 24.2μg/g, 22.7μg/g, 68.3μg/g, 534.8μg/g, 3.85%, 15.1μg/g. 25.6μg/g, 90.9ng/g, 0.4μg/g, 9.7μg/g and 0.470μg/g. Compared with Chinese Soil Element Background Value （CSEBV）, the pollution of heavy metal of urban street dust is very heavy, especially for Cd, Hg, Pb, Zn, and Cu, which are respectively 68.0, 17.1, 15.1, and 5.4 times than CSEBV, while the contents of urban soil and river sediment are basically same with CSEBV, except for Hg and Cd. Compared with other cities （street dust） and rivers （sediment）, the contents of heavy metal elements of urban street dust are higher than other cities’, and the contents in urban soil and river sediment are moderate. The analyses of Correlation and Cluster show that in urban street dust of Baoji, the heavy metal elements （Pb, Zn, and Mn） mainly originate from anthropogenic activities （modern industry, commerce, and traffic）, and that the heavy metal elements （Cd, Hg, Fe, Co, Ni, As, Cu, and Cr） mainly come from natural sources.3. The relationships between heavy metal elements and physical-chemical items in urban street dust and urban soil of Baoji and river sediment of Baoji section in Weihe River are studied by means of Correlation Analysis. The analytical results show that in urban street dust of Baoji, there are significant correlation between LF, HF, FD and many heavy metal elements, but there is no correlation between clay, silt, sand and heavy metal elements, while in urban soil of Baoji and river sediment of Baoji section in Weihe River, the relationships are just adverse, and that there are significant correlation between constant elements and many heavy metal elements in urban soil and river sediment. The distribution of heavy metal elements in different grain size is researched using physical filtration, plus XRF. The results show that in urban soil of Baoji and river sediment of Baoji section in Weihe River, the difference of distribution of heavy metal elements in different grain size is not quite clear.4. The speciations of heavy metal elements （Cu、Pb、Zn、Mn、Fe、Co、Ni、Cr, and Cd） in urban street dust and urban soil of Baoji and river sediment of Baoji section in Weihe River are researched utilizing modified-BCR sequential extraction procedure, plus ICP-MS and Inductively Coupled Plasma Atomic Emission Spectrometer （ICP-AES）. The results show that in urban street dust of Baoji, the order of mobility of heavy metal elements with environmental conditions is Cd （90.11%） > Pb （82.33%） > Zn （79.32%） > Cu （62.35%） > Mn （51.48%） > Co （29.02%） > Ni （23.62%） > Cr （18.68%） > Fe （10.21%）; that in urban soil of Baoji, the order is Pb （68.75%） > Cd （63.93%） > Co （59.25%） > Mn （57.32%） > Zn （29.01%） > Cu （25.94%） > Ni （20.70%） > Cr （15.36%） > Fe （7.30%）; that in river sediment of Baoji section in Weihe River, the order is Mn （56.70%）≈Pb （56.65%） > Cd （53.66%） > Co （48.82%） > Cu （43.99%） > Zn （21.93%） > Ni （15.49%） > Cr （11.43%） > Fe （9.62%）; and that urban street dust has bigger potential risk than urban soil and river sediment.5. The level of heavy metal pollution in urban street dust and urban soil of Baoji and river sediment of Baoji section in Weihe River at present is assessed by means of Müller’s Geo-accumulation Pollution Index and Lars Hakanson’s Potencially Ecological Risk Index. The results show that urban street dust of Baoji is mainly polluted by the heavy metal elements of Cd, Hg, Pb, and Zn et al; that urban soil of Baoji and river sediment of Baoji section in Weihe River are contaminated by Hg and Cd; that the heavy metal pollution of urban street dust is heavier than urban soil and river sediment.更多还原