Vertical and horizontal distribution of magnetic susceptibility and metal contents in an industrial district of central Iran Salman Naimi, Shamsollah Ayoubi ⁎ Department of Soil Science, College of Agriculture, Isfahan University of Technology,, Isfahan 84156–8311, Iran abstract article info Article history: Received 28 November 2012 Accepted 24 June 2013 Available online 3 July 2013 Keywords: Metals Magnetic properties Contamination factors Distribution of metals Industrial activities Vertical and horizontal distribution This study was conducted to determine the vertical and horizontal distribution of selected metals and magnetic susceptibility (χlf) in an industrial site located in Isfahan province, central Iran. For this purpose, we used a grid sampling methodology and excavated 202 profiles. Soil samples were then collected from 0–30, 60–90, and 120–150 cm depths. The mass magnetic susceptibility (χ) of the soil samples was measured at both low and high frequencies (χlf and χhf) using the Bartington MS2 dual frequency sensor; and χfd was also calculated. Soil samples were also analyzed for iron (Fe), manganese (Mn), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), chro- mium (Cr) and cobalt (Co) concentrations. The results showed that there were positive significant correlations among selected metals including Zn, Pb, Fe and Mn, which were mainly added through coal fly ash from an iron smelting factory at the studied site, while the concentration of Ni, Cr and Co was mainly controlled by the par- ent material of the soils. The trends in results at the site of study were similar in vertical and horizontal distribution for the industrial originated metals as judged by pollution load index (PLI) using χlf. The results of SEM/EDX also confirmed the presence of spheroid of magnetic particles in the surface soil samples taken in close proximity of the factory. Based on the results using the contamination factors (CF) determined for selected metals, the following order was observed: Pb N Zn N Mn N Fe N Cu N Ni ≥ Co N Cr. The results also suggested that magnetic methods could be used to estimate the metal contamination from anthropogenic sources in industrial soils. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Soil pollution is a serious environmental issue throughout the world (Gallego et al., 2002; Mico et al., 2006). Among the soil pollutants, heavy metals are especially hazardous due to their toxicological importance in ecosystems and human health (Facchinelli et al., 2001; Mico et al., 2006). It is generally considered that heavy metals accumulated in soils come from two primary sources natural (e.g. parent material weathering) (Nanos and Rodríguez Martín, 2012), and anthropogenic (e.g. metalliferous industries and mining, vehicle exhaust, agronomic practices, etc.) (Zhang, 2006). Various sources have been reported in lit- erature that are involved in the enrichment of metals in soils including vehicle exhaust, metal ore processing and smelting, mining, milling op- erations (Davies, 1997), as well as the agricultural production practices such as organic and mineral fertilization, the application of pesticides and irrigation water (Romic and Romic, 2003). Due to increased industrialization, the problem of environmental pollution has been increasing for the past several decades (Karimi et al., 2011). These problems are caused by the disposal of industrial wastes whether solids, liquids or gases, which have the potential to pollute the soil. Several studies have shown that the area in close proximity of the industrial activity leads to the contamination of soil, water and crops (Miro et al., 2004). Magnetic properties of soils reflect the effects of soil mineral compo- sition, especially the quantity of ferrimagnetic minerals. Magnetic sus- ceptibility measurements can serve a variety of applications including the changes in soil forming processes and ecological services (Singer et al., 1996), study of parent material and lithological effects (e.g., Lu, 2000), understanding sedimentation processes (Caitcheon, 1993), soil drainage (Mathe and Leveque, 2003), and soil redistribution (Ayoubi et al., 2012; Mokhtari Karchegani et al., 2011; Rahimi et al., 2013). The magnetic measurement is increasingly used as a tool for the de- tection of heavy metal contamination in soils and sediments caused by industrial emissions (Dankoub et al., 2012; Karimi et al., 2011). Magnet- ic measurements have been shown to be an effective proxy for investi- gating pollution by industrial and exhaust emissions, and other atmospheric pollutants (Lu et al., 2007). This method is based on the fact that industrial activities such as the combustion of fossil fuel that produce fly ash contain a significant fraction of magnetic minerals (Flanders, 1994). Thompson and Oldfield (1986) reported that soils near urban and industrial zones have increased χlf, which is attributed to the deposition of magnetic particles such as dust from metallurgical industry and fly ash produced by the combustion of coal. Using geochemical analysis, additional data can be obtained; and in combination with magnetic data, polluted areas can be characterized to determine the relative contribution by geologic and anthropogenic Journal of Applied Geophysics 96 (2013) 55–66 ⁎ Corresponding author at: College of Agriculture, Isfahan University of Technology, Isfahan, Iran. Tel.: +98 311 3913475; fax: +98 311 3913471. E-mail address: ayoubi@cc.iut.ac.ir (S. Ayoubi). 0926-9851/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jappgeo.2013.06.012 Contents lists available at ScienceDirect Journal of Applied Geophysics journal homepage: www.elsevier.com/locate/jappgeo