Assessment of heavy metal pollution in soil and their implications within and around mechanic villages

Analysis of nine composite soil samples, each made of three replicate core samples and their respective background samples collected from Okigwe, Nekede and Orji automobile mechanic villages were conducted. Metal concentrations (mg/kg) above the background levels in the top 100 cm soil profile ranges as follows: 748-70,606 (+/- 10114.3) for iron; 99-1090 perpendicular to 251.3 for lead; 186-600 perpendicular to 180 for manganese; 102-1001 perpendicular to 201.9 for copper; 8-23 perpendicular to 12.9 for cadmium; 4-27 +/- 6.0 for chromium; and 3-10 +/- 2.2 for nickel. The order of abundance is: iron > lead > manganese > copper > cadmium > chromium > nickel, with Okigwe > Nekede > Orji. Pollution indexes show that the metals have similar pollution trends in the three layers (L-1-L-3), with L-1 (0-10 cm) > L-2 (10-20 cm) > L-3 (90-100 cm) in Okigwe, L-3 >L-1>L-2 in Nekede, and L-3 >L-2 >L-1 in Orji. In effect, the shaly Okigwe soil is more polluted in the top layer while the sandy Nekede and Orji are more polluted in the lower layers. Despite this order, metal bioavailability may be less in the Okigwe soil due to its high clay-silt content (47 %-64 %). Pollution factor for Okigwe is 0.8, Nekede is 0.7 and Orji is 0.5. Nekede is under severe to excessive pollution while Orji and Okigwe are under moderate to excessive pollution, with weathered depths 7.4m at Orji and Nekede and 4m at Okigwe as most implicated in the pollution process. Above provides the bases for introducing the innovative concepts of environmentally friendly mechanic village.