Distribution Pattern of the Heavy Metals: Pb, Zn, Cd and Cu in Roadside Soils of Maiduguri Metropolis, Borno State Nigeria

In this research work the level of the metals: Pb, Cd, Zn, and Cu were determined in soil samples collected within Maiduguri Metropolis. Samples were collected from places of high anthropogenic activity such as automobile maintenance workshop (AMW), Car park or Bus stops (CP), and the highways (HW) to places of low activity the Residential areas (RA) at the depth of 5 to 15cm. To avoid washing away by rainfall, all collections were done during the dry season in the month of September/October 2012 to April/May of the following year 2013. These periods are period of incessant wind and sandstorm marked with low or no rainfall in this part of the country (far north-eastern part of Nigeria). Soil samples were analyzed using ICP-OES following digestion with aqua-regia and the results shows that; the AMW has the highest level of 180.96±3.84 µgg-1 for the metal Pb, whereas the levels, 200.15±10.81, 124.05±6.52, and 1.39±1.28 µgg-1 for the metals: Zn, Cu, and Cd respectively were observed in the samples from the Highways. Residential areas received the lowest values of 93.28±3.66, 26.76±3.43, and 0.40±0.54 µgg-1 for the metals; Cu, Pb and Cd respectively. The least value 113.82±16.02 µgg-1 for Zn was observed in the samples from the car parks or bus stops. The variation of the level of contamination by the metals: Pb, Cd, Cu and Zn with the high levels from places of high anthropogenic activity indicate the high level of contribution by vehicles. It also showed that the level of the metals observed in the samples from the residential areas may be attributed to atmospheric deposition of the metals carried from the highly anthropogenic places or from extraneous sources and not only a function of soil type.