Application of Soil Magnetic Susceptibility for Monitoring Bioavailable Metals Pollution

A novel method of monitoring soil pollution by heavy metals is using magnetometry as a cost-effective, simple, efficient, and fast method. In the present study, the potential of the magnetometric method to monitor the plant nutrient elements such as iron, manganese, zinc, and copper in the bioavailable fraction was evaluated. Also, their relationship with the greenhouse soil physicochemical characteristics of two towns of Isfahan Province (Dehaqan and Shahreza) were investigated. A total of 40 topsoil samples were collected (0-20 cm depth) from the study area in summer 2014 and the magnetic susceptibility (χ) of the collected samples was measured at both low and high frequencies (χlf and χhf) using the Bartington MS2 dual frequency sensor. The results indicated that there were no significant correlations between the soil magnetic susceptibility and the bioavailable forms of Cu, Zn, and Mn in the whole of the study area. This could be probably due to lack of penetration of these elements into the lattice structure of the ferromagnetic materials. The negative correlations between magnetic susceptibility and Fe showed that the increase of the bioavailable concentration of Fe is not necessity related to its high contents in the soil magnetic structure, so, it would not affect magnetic susceptibility positively. In addition, there was positive significant correlation between the magnetic susceptibility and clay and silt content as well as a negative significant correlation with sand content. Also, the low values of soil magnetic susceptibility in the bioavailable fraction (30.30 15±"> 7.89 15×"> 10-8 m3 kg-1) reflects the dominant effect of the bedrock and the inherent characteristics of soil on metals concentrations in the region. Based on this study, it can be concluded that in order to monitor the heavy metals in the bioavailable fraction of soils, and also in areas that are not affected by certain sources of pollution, monitoring techniques based on magnetic susceptibility do not have high efficiency.