Relationships between magnetic susceptibility and heavy metals in urban topsoils in the arid region of Isfahan, central Iran Rezvan Karimi, Shamsollah Ayoubi ⁎, Ahmad Jalalian, Ahmad Reza Sheikh-Hosseini, Majid Afyuni Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan, 84156–83111, Iran abstract article info Article history: Received 4 September 2010 Accepted 15 February 2011 Available online 23 February 2011 Keywords: Heavy metals pollution Isfahan Magnetic susceptibility Urban soils Recently methods dealing with magnetometry have been proposed as a proper proxy for assessing the heavy metal pollution of soils. A total of 113 topsoil samples were collected from public parks and green strips along the rim of roads with high-density traffic within the city of Isfahan, central Iran. The magnetic susceptibility (χ) of the collected soil samples was measured at both low and high frequency (χlf and χhf) using the Bartington MS2 dual frequency sensor. As, Cd, Cr, Ba, Cu, Mn, Pb, Zn, Sr and V concentrations were measured in the all collected soil samples. Significant correlations were found between Zn and Cu (0.85) and between Zn and Pb (0.84). The χfd value of urban topsoil varied from 0.45% to 7.7%. Low mean value of χfd indicated that the magnetic properties of the samples are predominately contributed by multi-domain grains, rather than by super-paramagnetic particles. Lead, Cu, Zn, and Ba showed positive significant correlations with magnetic susceptibility, but As, Sr, Cd, Mn, Cr and V, had no significant correlation with the magnetic susceptibility. There was a significant correlation between pollution load index (PLI) and χlf. PLI was computed to evaluate the soil environmental quality of selected heavy metals. Moreover, the results of multiple regression analysis between χlf and heavy metal concentrations indicated the LnPb, V and LnCu could explain approximately 54% of the total variability of χlf in the study area. These results indicate the potential of the magnetometric methods to evaluate the heavy metal pollution of soils. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Dust that accumulates on soils and roadsides in the urban and industrial areas is indicator of heavy metal contamination from atmospheric deposition (Culbard et al., 1988). Method based on the Magnetometric properties of soils are increasingly applied as proxy methods for evaluating the heavy metal pollution of soils, sediments and dusts, because such methods are rapid, inexpensive and non- destructive and can be used for mapping of the contaminated soils (e.g., Wang and Qin, 2005). In addition, the interest in the use of magnetometric methods is increasing because of their rapidity as a single measurement of soil samples makes it possible to establish dense grids of sampling sites (Hanesch and Scholger, 2002). There have been numerous studies linking the magnetic properties of soils to the urban contamination in a variety of environments. For example, Lu and Bai (2006) reported that soils near urban and industrial areas had an increased magnetic susceptibility, which they attributed to the deposition of magnetic particles such as dust from the metallurgical industry and fly ash from coal combustion. Strzyszcz and Magiera (1998) reported relatively high correlation coefficients between concentrations of Zn, Pb, and Cd in forest soils of the Upper Silesian industrial regions (Southern Poland) and magnetic suscep- tibility. Magnetic properties and heavy metal concentration (Cu, Cr, Pb, Ni, and Zn), which were measured on vibracore samples, were found to be potential indicators of the contamination of seabed sediments due to the shipping activities in the Hong Kong Harbor (Chan et al., 2001). The whole-core magnetic susceptibility measure- ments showed a higher concentration of magnetic particles in the surface layer of the sediment cores, and significant correlations were observed between the magnetic susceptibility and concentrations of Pb, Zn and Cu, as well as the Tomlinson pollution load index (PLI). Lecoanet et al. (2003) assessed the potential of the magnetic techniques to determine the contaminating emission sources and its effects on the contamination of surface and bottom soil samples. The results showed that the contents of magnetic minerals with higher magnetic coercivity increased with depth from surface to the bottom in the soil profiles. The scanning electron microscopy (SEM) analysis was used to study the surface soil samples collected from Xuzhou, a large industrial city in China that is a center for mining and heavy industries Journal of Applied Geophysics 74 (2011) 1–7 Abbreviations: χlf, Low frequency magnetic susceptibility; χhf, High frequency magnetic susceptibility; χfd, Frequency-dependent susceptibility; As, Arsenic; Cd, Cadmium; CU, Copper; Ba, Barium; Sr, Strontium; Cr, Chromium; V, Vanadium; Mn, Manganese; Zn, Zinc; Pb, Lead; MS, Magnetic susceptibility; PLI, Pollution load index; K–S, Kolmogorov–Smirnov; Fe, Iron; EC, Electrical conductivity; pH, Soil acidity; SOM, Soil organic carbon; CCE, Calcium carbonate equivalent; CEC, Cation exchangeable capacity. ⁎ Corresponding author. Tel.: + 98 3113913470; fax: + 98 3113913471. E-mail address: ayoubi@cc.iut.ac.ir (S. Ayoubi). 0926-9851/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jappgeo.2011.02.009 Contents lists available at ScienceDirect Journal of Applied Geophysics journal homepage: www.elsevier.com/locate/jappgeo