Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal
Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal
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DOI：
10.1016/j.geoderma.2013.07.035
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发表时间：
2014-01-01
期刊：
影响因子：
6.1
通讯作者：
Gomes, C. R.
中科院分区：
文献类型：
--
作者：
Lourenco, A. M.;Sequeira, E.;Gomes, C. R.
本研究提出了一个应用环境磁学技术的表征附近的科英布拉（葡萄牙中部）的土壤。对在6个土壤剖面中采集的样品进行了磁性测量、扫描电子显微镜和地球化学研究，以找出可能的关系并解释环境影响。在100 mT和300 mT的背场下测量了磁化率、饱和等温剩磁和等温剩磁。还计算了硬度%、SIRM/chi和S比。污染土壤表现出较高的值磁参数在表层土壤层接近道路，植物和城市地区。最低值出现在土壤的深层和受人类活动干扰最少的地区。磁性结果还表明，这些土壤的磁信号主要是由亚铁磁性磁铁矿类矿物的影响，只有一个较小的贡献，从反铁磁性载体（如赤铁矿矿物）。在未受污染的土壤中，成岩作用的贡献反映在母岩材料附近磁化率的增强。表层土样品的扫描电子显微镜图像显示，存在典型的车辆废气和燃烧过程的磁性小球。这一证据表明，大气沉降的粉煤灰是在表土中的磁信号增强的主要原因。化学分析表明，各种重金属的浓度高于平均背景值的葡萄牙土壤，更高的表层土壤。重金属含量与磁性呈显著正相关。这些结论强调了环境磁学方法和技术在评价土壤演变和污染历史过程中的重要性。(C)2013爱思唯尔有限公司版权所有。
This study presents an application of environmental magnetism techniques for the characterisation of the soils near Coimbra (central Portugal). Magnetic measurements, scanning electron microscopy and geochemical studies were carried out on samples collected in 6 soil profiles in order to find possible relationships and to interpret environmental implications. Magnetic susceptibility, saturation isothermal remanent magnetisation and isothermal remanent magnetisation at the backfield of 100 mT and 300 mT were measured. HardIRM %, SIRM/chi and S-ratios were also calculated. Polluted soils showed higher values of magnetic parameters in the superficial soil horizons closer to the roads, plants and urban areas. The lowest values were observed in the deeper horizons of the soil and in the areas least disturbed by human activity. The magnetic results also suggested that the magnetic signal of these soils is mainly influenced by ferrimagnetic magnetite-like minerals and with only a minor contribution from antiferromagnetic carriers (such as hematite minerals). In unpolluted soils, lithogenic contribution is reflected by the enhancement of magnetic susceptibility near parental rock material. Scanning electron microscope images of the topsoil samples revealed the presence of magnetic spherules typical of vehicular exhaust and combustion processes. This evidence suggests that the atmospheric deposition of fly ash is the main reason for the enhancement of the magnetic signal in the topsoil. Chemical analyses showed that the concentration of various heavy metals was higher than the mean background values for Portuguese soils, and higher in superficial soils. Heavy metals showed significant positive correlation with magnetic properties. The conclusions highlight the importance of using environmental magnetism methods and techniques in the evaluation process of soil evolution and pollution history throughout time. (C) 2013 Elsevier B.V. All rights reserved.