Abstract
Aim: This paper deals with the estimation of pollution indices of metals in the soils of Abuja metropolis and the soils were taken from residential, industrial, motor parks, near mechanic and urban forest areas within the metropolis.
Methods: Sequential extraction technique using Flame atomic absorption spectrometer was used to generate data which was used eventually to estimate mobility and contamination factors and also pollution load index of metals under study..
Results: Findings revealed metals above limits and therefore hazardous to humans and environment in the mobility factors and were found to be: Pb(33-99), Fe(47-54), Ni(64), Zn(67-93), Al(51-66), Mn(49-81), Cr(77-95) and As(53-65) for urban soils. Metals with high mobility factor in sub-urban soils were found to be: Pb(33-99), Fe(47-54), Ni(64), Zn(67-93), Al(51-66), Mn(49-81), Cr(77-95) and As(53). Metals with contamination factors above limits for urban soils include: Ni(17), Al(2.94) and Cr(36.70) . Metals in sub-urban soils with high contamination factor were: Al(3.94) and Cr(6.70). Metals with pollution load indices above limits were found to be: Pb(2.56), Cd(6.55), Fe(7.60), Ni(25.32), Zn(2.15), Al(7.96), Mn(2.85), Cu(4.58), Cr(39.81) and As(8.41). Metals with high pollution load indices in sub-urban soils were: Pb(1.33), Cd(4.04), Fe(4.33), Ni(14(52), Zn(2.53), Al(7.13), Mn(4.77), Cu(3.53), Cr(15.60) and As(7.61) respectively.
Conclusion: The results showed that some metals in Abuja soils had high pollution indices which made them contaminants in the environment. Excess Fe, Zn, Mn can cause phytotoxicity in plants which hinders photosynthesis and can increase the level of CO2 in the atmosphere thereby causing global warming in Abuja metropolis. Excess Cu can cause retardation of decomposition of organic matter in soils by microbes, which affects nitrogen and carbon cycles in the environment thereby affecting soil balance. Relevant authorities should carry out periodic environmental risk assessments on Abuja soils towards curbing excess Fe, Zn, Mn, Cu and other metals under study in Abuja metropolis for a sustainable environment

Key words: Abuja metropolis, Pollution indices, Phytotoxicity, Urban soils, Sub-urban soils and Global warming