Magnetic susceptibility measurement and heavy metal pollution at an automobile station in Ilorin, North-Central Nigeria

Magnetic susceptibility measurement was carried out on 26 top-soil samples randomly collected from the study area and 5 selected top-soil samples outside the station, using the Bartington MS meter linked to a computer operated using Multisus2 software. The Measurements was done at both low (0.47 kHz) and high (4.7 kHz) frequency susceptibilities which was further used to calculate the frequency dependent susceptibility (X-FD). The values for low frequency mass magnetic susceptibility ranges between 96.6 x 10(-5) m(3) kg(-1) and 146 x 10(-5) m(3) kg(-1) with an average value of 117.35 x 10(-5) m(3) kg(-1) and standard deviation of 12.22 x 10(-5) m(3) kg(-1). The result reveal high magnetic susceptibility values at the station compared with the values observed outside the station which ranges between 53.0 x 10(-5) m(3) kg(-1) and 72.3 x 10(-5) m(3) kg(-1) with an average value of 63.2 x 10-5 m(3) kg(-1) and standard deviation of 7.01 x 10(-5) m(3) kg(-1). This significant magnetic enhancement indicates high concentration of ferrimagnetic minerals in the soil and thus evidence of pollution due to the activities at the station which implies that the magnetic enhancement is of anthropogenic source than pedogenic and lithogenic. Analysis of the heavy metals also reveals higher values at the station. The correlation analysis between the mass specific magnetic susceptibility and the heavy metals concentrations (i.e. Cu (R = 0.92), Fe (R = 0.88), Cr (R = 0.85), Zn (R = 0.83), Cd (R = 0.79), Mg (R = 0.72), Mn (R = 0.60), Pb (R = 0.67)) which was conducted to further investigate the relationship between the soil magnetic susceptibility values and elemental variations, demonstrated magnetic susceptibility can be used as a proxy method for assessing the pollution of these heavy metals.