枣庄市城乡接合部农田表土环境的磁学特征

Magnetic Characteristics of the Farmland Topsoil in Rural-Urban Fringe Zone of the Zaozhuang City

为验证运用环境磁学方法监测城乡接合部农田土壤污染情况的可行性,利用磁测并结合扫描电镜、能谱分析法对枣庄市市中区城乡接合部的农田表土开展了自然土壤的磁学性质及成因对比分析。结果表明,研究区自然土壤、远离和近道路农田区的表土样品均以亚铁磁性磁铁矿为主,分别具有单畴、假单畴和多畴颗粒特征,农田表土与自然土壤相比其磁性整体显著增强;自然土壤磁性提取物粒径普遍小于1μm,而农田表土磁性物质呈大颗粒不规则状,主要分布在数微米至80μm之间;近道路农田区表土中粗颗粒磁性物质及其携带的重金属元素含量均高于远离道路农田区。研究表明,人类活动产生的强磁性颗粒外源输入是农田表土磁性增强的主要原因,表征磁性矿物含量的磁学参数是监测城乡接合部地区农田土壤环境和快速判断污染物来源的有效方法。

In order to verify the feasibility of monitoring farmland soil pollution in the rural-urban fringe zone(RUFZ)by the method of environmental magnetism,the magnetic measurement,scanning electron microscopy and energy dispersive spectrometer are applied to investigate the magnetic features and genesis of the farmland and natural soils in the RUFZ of the Zaozhuang City.The results show that the magnetic minerals in natural soil,topsoil samples from farmlands that close to and far from the roads are all dominated by the ferromagnetic magnetites,displaying the single domain,pseudo-single domain and multi-domain characters respectively;meanwhile,the farmland topsoil samples show enhanced magnetism comparing with that of the natural soil.The physical size of magnetic extract of the natural soil is generally less than 1μm,while the magnetic materials in the farmland topsoils are relatively large particles and irregular in shape,ranging mainly from several micrometers to about 80μm.And the roadside farmland topsoil samples have a higher content of coarse-grained magnetic particles and heavy metal elements than those of the samples from the farmlands far from the roads.It is revealed that the magnetic enhancement of the farmland topsoil samples is principally attributed to the input of materials with strong magnetism generated by the human activities.The magnetic parameters indicating the content of ferromagnetic mineral are proved to be an effective way of tracking the farmland soil environment and efficiently recognizing the pollutant sources in the rural-urban fringe zones.