Concentration of Heavy Metals in Soil and Plants Along Mubi-gombi, Roadside, Adamawa State, Nigeria

This study was aimed at determining the elemental concentrations of heavy metal pollutants that may be present in soil and plant samples along Mubi – Gombi roadside Adamawa state, Nigeria. The concentrations of selected heavy metals (Zn, Cr, Mn, Ni and Cu) along Mubi - Gombi roadside were analyzed. Samples of roadside surface soil and plant were collected from six towns; these include Mubi, Mararaba, Makera, Kala’a, Hong and Gombi. Samples of soil and plant were taken in each town at a distance of 5 m, 10 m and 15 m away from the edge of the road. The samples were digested using aqua regia digestion method. Subsequently, the concentration of these metals was analyzed using Atomic Absorption Spectrophotometer. The result revealed that Zn, Cr, Mn, Ni and Cu were present in the studied soil and plant samples. The mean concentrations ranged from Zn (9.19 ± 1.31 –13.40 ± 3.01 mg/kg) Cr (0.01 ± 0.00 – 0.03 ± 0.01 mg/kg), Mn (11.02 ± 2.51 –13.52 ± 3.32 mg/kg), Ni(0.04 ± 0.01- 0.12 ± 0.04 mg/kg), and Cu(0.07 ± 0.02 - 0.26 ± 0.08 mg/kg) in the soil samples, while the mean concentration in plant leave samples ranged from Zn (7.10 ± 1.21- 11.28 ± 2.81 mg/kg), Cr (0.01 ± 0.00 - 0.02 ± 0.00 mg/kg), Mn (9.43 ± 1.82 - 12.81 ± 2.53 mg/kg), Ni (0.01 ± 0.00 - 0.09 ± 0.02 mg/kg) and Cu (0.03 ± 0.01 - 0.19 ± 0.07 mg/kg). The concentration of Mn and Ni exceeded the permissible limit of WHO. While the concentration of Zn, Cr and Cu were found to be within WHO limit. The high levels of Mn and Ni indicate the potential health risk for human. The high level of these metals might be due to anthropogenic activities. However, the values of these heavy Metals decreased with increasing distance away from the edge of the road. The result of the transfer factor showed that only Mn at Mubi has the highest value of 1.07 which shows that plants were enriched by Mn from the soil, followed by Ni at Mubi and Cr at Gombi with the value of 1.00. While the values of Zn and Cu was below 1.00 at all the studied sites. There was strong positive correlation for all the metals studied which implies that plants absorb the metals from the soil through their root. It could also mean that roadside soil and plants contamination by metals originated from a common anthropogenic source; with probably automobiles as a major common source. Therefore economic plants should not be planted along the highway to avoid heavy metal contamination.