Levels of trace metals in soil and vegetation along major and minor roads in metropolitan city of Kaduna, Nigeria

Abstract

Sample of soil and plant (Sida acuta burm F.) were collected from 30 sites of 24 roads. The samples were analyzed for Pb, Cd, Zn, Cu and Mn using flame atomic absorption spectrophotometry. The soil physico-chemical parameter, pH and particle size distribution was also determined. Levels of Pb, Cd,Zn, Cu and Mn in soil were 15.28 – 76.92, 1.96 – 9.80, 41.66 – 237.96, 1.60 – 4.88 and 76.00 – 132.00 mg/kg dry weight, respectively. Results of concentrations in plants ranged were from trace – 32.37, 4.88 – 14.93, 27.78 – 185.19, 1.67 – 3.89 and 20.00 – 110.00 mg/kg dry weight for Pb, Cd, Zn, Cu and Mn, respectively. The soil pH was from 6.22 – 8.44 while sand and loamy sandy textural classes constitute the soil samples. For both experimental soil and plant samples, the mean concentrations were found to follow the decreasing orders; Zn > Mn > Pb > Cu > Cd and Zn > Mn > Pb > Cd > Cu, respectively. Mild correlation between traffic density and metals in samples with the exception of plant Pb content, suggest that automobile emission couple with waste dispose along the roads remain a threat. The findings in general indicate the levels of metals in soil and plant samples were within the EU limits with the exception of Cd. In addition, the high level of Cd appears to reach pollution levels and metal dynamics up the food chain is highly possible.