西安市公园土壤的重金属含量水平及理化性质研究

【作者】 黄静；

【导师】 卢新卫；

【作者基本信息】 陕西师范大学 ， 环境科学， 2009， 硕士

【摘要】 随着城市化的发展,城市土壤环境质量状况日益受到关注。城市土壤作为城市生态系统的重要组成部分,是城市绿色植物的生长介质和养分的供应者。公园绿地系统是市民娱乐休闲和接触自然的主要场所,然而,公园绿地土壤正遭受城市活动和城市化过程带来的环境压力,造成土壤质量降低或破坏,致使其本身生产、生态功能发生转变或者彻底丧失。同时,重金属元素在土壤中的积累,会对人体健康产生不良影响,尤其是儿童。因此研究城市公园土壤的理化性质和重金属含量水平,对于讨论城市土壤质量和重金属的来源、评价土壤质量状况和污染现状具有重要的现实意义。本文选取西安市区19个典型公园土壤作为研究对象,经过野外调查采样和实验分析,系统研究了西安市城区内典型公园的理化特性,其中包括土壤质地、pH值、电导率、磁化率、烧失量、碳酸钙、有效磷、速效钾和常量组分。利用X-Ray荧光光谱仪分析了土壤中重金属元素As、Cu、Mn、Pb、Zn、Co、Ni、Cr和Fe的全量。采用修正的内梅罗法对土壤样品肥力进行综合评价。运用内梅罗综合污染指数法和综合潜在生态风险指数法对土壤样品的重金属污染状况及潜在风险进行了分析。通过相关分析讨论了重金属之间的关系以及土壤理化性质与重金属含量之间的关系,主要结论如下:(1)西安市公园土壤质地类型为粉砂质壤土,粒径平均组成是黏粒为22.99%,粉粒为74.15%,砂粒为2.82%;西安各公园烧失量差异较小,平均值为3.89%;土壤呈偏碱性,部分地区呈现强碱性;电导率(EC)值0-0.5 ms/cm,处于园林植物生长安全范围之内,没有出现盐渍化的问题;碳酸钙含量范围在27.78～126.19g/kg之间,平均值为95.96 g/kg;有效磷和速效钾含量在西安市公园表层土壤中富集。土壤综合肥力评价结果表明供试土壤整体的肥力状况处于中等水平(1.0≤P<1.5)。各公园内的综合肥力系数差异不大。(2)与陕西省土壤背景值相比,As、Cu、Mn、Pb、Zn、Co、Ni、Cr、Fe各元素在西安公园土壤中发生了明显的积累,依次为Pb>Cu>Co>Fe>Zn>Cr>Mn>Ni>As。Pb在革命公园、莲湖公园、环南公园、环城西苑达到较高污染水平;Zn在莲湖公园、环南公园污染程度较高;Cu在莲湖公园和劳动公园土壤高度污染。内梅罗综合污染指数法评价结果表明西安市公园土壤均受到不同程度的污染,其中有4个公园属于重度污染;9个公园属于中污染;其余6个公园为轻污染。重度污染的公园多数位于城墙以内;城墙与二环间的公园,多数属于中等污染。潜在生态指数法表明西安市各公园土壤重金属生态风险处于中等水平,各元素的潜在生态风险指数大小顺序为Pb=As>Cu>Cr>Mn>Zn。(3)对西安市公园不同深度土壤的研究表明,由于城市的建设,如建筑、修路等以及工业废弃物、生活垃圾、交通运输废气等的排放,城市土壤剖面常遭受严重改变,土壤中有许多不同来源物质的混入,最终导致自然土壤发生层被破坏,许多土壤剖面上下土层无发生学上的联系,重金属含量在剖面上的分布无规律。(4)土壤理化指标与重金属含量相关显示,pH、烧失量、低频磁化率、高频磁化率、频率磁化率、碳酸钙、黏粒、粉粒、砂粒与多数重金属含量的相关性较好,反映了上述理化指标是影响多数重金属富集的主要因素,说明城市公园表层土壤已受到人类活动的干扰。(5)Pb、Zn、Cu元素之间相关性显著,Cr与Ni、Co、Fe的三种元素相关性显著,表明Cu、Zn、Pb三种元素的来源有较大的相似性,Mn与As、Ni、Co、Fe相关性较显著;Cu与Cr、Mn、As、Ni、Co、Fe相关系数较小,表明具有相同源的可能性小,同时又说明城市公园土壤在接受外来污染时来源的复杂性。更多还原

【Abstract】 With rapid development of urbanization, Environmental quality of urban soils is becoming increasingly concerned. Urban soil that was regarded as the major factor of sustainable development of urban areas is the important part of ecosystem, site and nrtrition supplier for vegetation. The city park is the main places for the citizen to relax and to get in touch with the natural world, however, the city park soil is facing the environmental problems from urbanization process, such as quality of soils is becoming worse, its roles for production and ecology is changing or losing. At the same time, the accumulation of heavy metals in the soil will have a negative impact on human health, especially children. So the study of the physical -chemical property and heavy metal concentration levels in urban park soil, for discussion of urban soil quality and the sources of heavy metals, evaluation of soil quality and soil pollution have important practical significance.The study concentrated on 19 parks in Xi’an city. After field investigation and laboratory analysis of soil samples, systematically studied the physical-chemical property in Xi’an typical city park, such as particle size, pH, conductivity（EC）, loss on ignition, magnetic susceptibility, CaCO₃ contents, available P and available K contents and constant elements of soil. The concentration of As, Cu, Mn, Pb, Zn, Co, Ni, Cr and Fe in soil was analyzed by using X-Ray fluorescence spectrometry. The integrated fertility evaluation was assessed by using the modified synthetic pollution index method. The contamination level and ecological risk of heavy metals in soils were assessed by using the synthetic pollution index method and potential ecological risk index method. Using correlation analysis to discuss the relationship between heavy metals and the relationship between soil physical - chemical property and heavy metal contents. The main conclusions of this paper is as follows:（1） Xi’an Park soil texture type is silty loam, the average particle size is composed of 22.99% clay, 74.15% silt , 2.82% sand; the LOI in every park has smaller difference, average value is 3.89%; soil in most park was alkaline, in some areas showed strong alkaline; conductivity （EC） values from 0 to 0.5 ms / cm that within the scope of garden plant safe to grow , there was no problem of salinization; calcium content in the range of 27.78～126.19g/kg ,average value is 95.96 g / kg; available phosphorus and potassium contents are enrichment in surface soils of Xi’an Park. The results of comprehensive evaluation of soil fertility show that the overall fertility status of soil at the middle level （1.0≤P <1.5）. The discrepancy of fertility coefficient in different park is not evident.（2）Compared to Shaanxi Province background value of soil, As, Cu, Mn, Pb, Zn, Co, Ni, Cr, Fe elements in the soil in Xi’an park have been marked accumulation, followed by intensity of Pb> Cu> Co> Fe> Zn> Cr> Mn> Ni> As. Pb in the Revolutionary Park, Lianhu Park, Central South Park, Central west Park reach a higher level of pollution; Zn in Lianhu Park, Central South Park reach the higher the degree of pollution; Cu in Lianhu park and Laodong park highly contaminated in soil. The results of synthetic pollution index method show that all the Xi’an city park are subject to different levels of soil pollution, including four parks are heavily polluted; 9 parks are medium pollution; the rest of 6 parks are light pollution. Most of heavily polluted parks are located within the walls; parks between the walls and the second ring, which the majority belonged to the middle of pollution. Potential ecological index method shows that the parks in Xi’an ecological risk of heavy metals in soils at the middle level, the order of every elements potential ecological risk index is Pb = As> Cu> Cr> Mn> Zn.（3） The study of different depth of the soil in Xi’an city park have shown that, due to the construction of city, such as construction, road repair, etc., as well as industrial waste, solid waste, transportation and other air emissions, urban soil profile often suffer serious change, there are many different source material is mixed in soil, and ultimately lead to the natural soil was damaged, many soil profile upper and lower layers didn’t have genetic contact, the distribution of heavy metals content in the profile is irregular.（4） In soil physical-chemical indicators associated with the heavy metal contents analysis, the correlation among pH, loss on ignition, low-frequency magnetic susceptibility, high-frequency magnetic susceptibility, frequency dependent susceptibility, CaCO₃ contents, clay, silt, sand and heavy metal contents is better, reflecting the above-mentioned physical-chemical indicators are the major impact factors of most heavy metal enrichment. The surface of the soil in city park has been affected by human activities. （5） Pb, Zn, Cu three elements have more significant correlation, more significant relevance between Cr and Ni, Co, Fe three elements, indicating that the sources of Cu, Zn, Pb three elements have a greater similarity, Mn and As, Ni , Co, Fe have significant correlation; Cu and Cr, Mn, As, Ni, Co, Fe less correlation coefficient, indicating the possibility of with the same source is small. At the same time it show that external contaminate source of city park soil is complex.更多还原