Spatial Pattern of Heavy Metal Accumulation under Different Urban Transportation Facilities in Lagos Metropolis

Abstract

The study examined the spatial pattern of heavy metal accumulation under different urban transportation facilities (roadside, railway, canal, airport, warehouse and bus stop) in Lagos Metropolis, Nigeria. Data were obtained by collecting thirty surface soil samples (0 – 15cm) from six transportation facilities in the Lagos metropolis. Soil samples were taken to the laboratory for analysis of heavy metals such as Cd, Cr, Cu, Fe, Ni, Pb and Zn using Atomic Absorption Spectrophotometer (AAS) technique. Results obtained showed the spatial variation of heavy metal to be in the order of Fe>Zn>Cu>Ni>Cr>Pb>Co>Cd. The order of transportation facilities was canal>airport>roadside>railway>warehouse>bus stop implying that canal, airport and roadside generated high quantities of metals. Pearson’s correlation showed positive and significant associations between Co and Cd (r = 0.587, p<0.05), Ni and Cr (r = 0.490, p<0.05), Ni and Co (r = 0.416, p<0.05), Zn and Cr (r = 0.539, p<0.05) and between Zn and Co (r = 0.838, p<0.05), while negative and significant association existed between Cr and Cd (r = -0.441, p<0.05).  The contamination factor showed low to very high contamination. The degree of contamination showed low to moderate degree of metal contamination across the different transportation facilities, while the pollution load index revealed the absence of metal pollution.