Comparison of magnetic susceptibility probes relevantly used in soil contamination applications

Magnetic susceptibility (MS) technology can achieve the efficient rough measurement, mapping, and pollution assessment of soil heavy metal concentrations in topsoil due to atmospheric dust contamination. However, previous studies of commonly used MS field probes (MS2D, MS2F, and MS2K) have not dealt with the range of magnetic signal detection and the attenuation characteristics of the signal with respect to distance. In this study, the vertical and horizontal measurement ranges of the MS2D, MS2F, and MS2K probes were explored through laboratory and field experiments, and the intensity of their magnetic signals was further compared and analyzed in the field. The results showed that the magnetic signal intensity of the three probes decreased exponentially with distance. The penetration depths of the MS2D, MS2F, and MS2K probes were 8.5, 2.4, and 3.0 cm, respectively, and the horizontal detection boundary lengths of their magnetic signals were 32, 8, and 6.8 cm, respectively. In the field surface soil MS detection, the magnetic measurement signals of the MS2F and MS2K probes showed a weak linear correlation with the MS2D probe (R² of 0.43 and 0.50, respectively), while the MS2F and MS2K probes had a significantly better correlation (R² = 0.68) with each other. In general, the MS2D probe and MS2K probe correlation had a slope close to unity, meaning MS2K probes had good mutual substitution. Furthermore, results of this study improve the effectiveness of the MS evaluation of heavy metal pollution in urban topsoil.