蚌埠市城区土壤剖面磁学性质及其环境意义

Magnetic Property of Urban Soil Profile in Bengbu City and Its Environmental Significance

为了研究人类活动对城市土壤环境的影响,作者在蚌埠市锥子山脚下(117.46°E,32.91°N)挖了1条旱地土壤剖面,测量了土壤剖面中矿物成分含量、重金属元素(Zn、Pb、Cr、Ni、Cu)含量和磁学参数(低频体积磁化率(κ_(L))、高频体积磁化率(κ_(H))、非磁滞剩磁(ARM)、等温剩磁(IRM、SIRM)、热磁曲线(κ-T曲线))值,并对测量数据进行了计算和统计分析。结果表明,土壤剖面主要含有石英、钠长石、钾长石、伊利石和蒙脱石等矿物,由于受到城市人类活动的影响,表层土壤中Zn和Pb的含量明显升高。土壤中磁性矿物有磁铁矿、赤铁矿、针铁矿和纤铁矿等,但含量较低,土壤剖面的磁学性质主要由亚铁磁性矿物主导。根据磁学参数随深度的变化关系可将土壤剖面分成两层,0~20 cm为第一层,20~80 cm为第二层。第二层土壤的磁学性质主要由土壤母质决定,第一层土壤由于受到城市人类活动所产生的强磁性颗粒物的影响,其磁化率(χ)、饱和等温剩磁(SIRM)和非磁滞剩磁磁化率(χ_(ARM))平均值大幅高于第二层,频率磁化率(χ_(fd))和χ_(ARM)/SIRM平均值低于第二层,反映第一层土壤中磁性矿物含量增加、粒径变粗。土壤剖面0~20 cm土壤的磁学参数值随深度的变化关系反映了城市人类活动对旱地土壤剖面的影响过程和程度。

In order to study the impact of human activities on urban soil environment,the soil profile of a plot of dry-land dug at the foot of the Zhuizi Mountain(117.46°E,32.91°N)in Bengbu City was investigated to examine its property regarding the content of mineral components and heavy metal elements(Zn,Pb,Cr,Ni,Cu);additionally,its magnetic parameters were measured including low-frequency volume magnetic susceptibility(κL),high-frequency volume magnetic susceptibility(κH),anhysteretic remanent magnetization(ARM),isothermal remanent magnetization(IRM,SIRM),temperature-dependent mag⁃netic susceptibilities(κ-T curve),and the measured data were calculated and statistically analyzed.The findings of the study reveals that the soil profile mainly consists of minerals such as quartz,albite,potassium feldspar,illite and montmorillonite;owing to the influence of human activities in the City,the content of Zn and Pb in the top soil was significantly increased;magnetic minerals in the soil includes magnetite hematite,goethite and lepidocrocite,but was relatively low,the magnetic properties of the soil profile are mainly dominated by ferrimagnetic minerals.According to the variation of magnetic parame⁃ters related with depth of the soil profile,the soil profile can be divided into two layers:0~20 cm being the first layer,20~80 cm the second layer.The magnetic property of the second layer of soil is mainly determined by the soil parent material,on the other hand,the first layer of soil has been affected by strong magnetic particles brought about by urban human activi⁃ties,the average values ofχ,SIRM andχARM being remarkably higher than those of the second layer,whileχfd andχARM/SIRM average values lower than those of the second layer,reflecting an increase in the content of magnetic mineral and coarsening of particles in the first layer of soil.The facts of magnetic parameter values vary with depth of the soil profile within 0~20 cm reflected the process and degree of influence on the dry-land soil profile,exerted by urban human activities.