Roadside Heavy Metals in Soil and Plants

Heavy metal concentration in roadside soil and plants are increasingly becoming of health concern.
Especially with the continue increase in anthropogenic activities such as industries and urbanization
which releases pollutants in to the environment without control and effects remedies. Heavy metal is
any metal that is toxic regardless of their density or atomic mass. Heavy metals occur naturally in the
soil environment from the pedogenetic processes of weathering of parent materials and from
anthropogenic sources such as traffic emission, industrial and energy production, waste disposal,
vehicle exhaust as well as coal and fuel combustion. Among the numerous environmental pollutants,
heavy metals plays an important role as its concentrations in air, soil and water are continuously
increasing due to anthropogenic activities. To determine heavy metals in roadside soil and plants,
Hong major road in Adamawa State, Nigeria was taken as a case study. The concentration of
selected heavy metals (Cd, Pb, Zn, Cr, Fe, Mg, Mn, Co, Ni and Cu) in roadside soils and plants
samples from selected sites (Plaifu, Shiwa, Fadama-rake and Damdrai) along major road in Hong
were determined. Soil samples were taken 10 m, 20 m and 30 m away from the edge of the road at
the depth of 0-10 cm, 10-20 cm and 20-30 cm. Plant samples were randomly collected within the
vicinity where the soil samples were taken and were analyzed using Atomic Absorption
Spectrophotometer. The result revealed the trend in soil heavy metal concentration was Fe > Mn >
Mg > Pb > Zn > Ni > Co > Cu > Cr > Cd and for plant the trend was Fe > Mn > Mg > Zn > Pb > Ni >
Cu > Cd > Co > Cr. The concentrations decreased with increasing distance away from the edge of the
road as well as with depth at which the soil sample were taken. The transfer factor showed that the
concentration of Zn, Mn, Cu and Mg were greater than 1, which shows that plant were enriched by Zn,
Mn, Cu and Mg from the soil. Mg and Cd equal to 1 at Plaifu and Damdrai. Most of the values of TF at
the study area super pass 0.5, which implies that generally, the ability of bioaccumulation of these
heavy metals in examined plants were relatively high.