Pollution Indices of Trace Metals in Urban Dumpsite Soils within Akwa Ibom State, Nigeria

Abstract

Surface soil samples were obtained from six (6) urban dumpsite soils namely: Uyo, Abak, Eket, Onna, Ikono and Ikot Ekpene within Akwa Ibom State, Nigeria. Control samples were also collected from a forest in Etinan local government area of the same State. Samples collected were treated and analyzed based on standard techniques to ascertain the pollution status of Pb; Cd; Ni; Cr and Fe at each dumpsite soil and Control using geoaccumulation index (Igeo) and Contamination factor (CF) analysis. The source of metals to dumpsite soils and Control was identified using enrichment factor model. Pollution status of each dumpsite soil was also established using degree of contamination (Cdeg). Igeo results showed that, Pb, Ni and Cr moderately polluted dumpsite soils studied, Cd varied between unpolluted to moderately polluted status. However, Fe indicated very low Igeo values indicating the low availability of the metal in the study area. Enrichment factor analysis showed that Pb and Cr were primarily from anthropogenic sources; Ni and Fe were mostly from natural source while Cd source varied between anthropogenic and natural at the different dumpsite soils but the source of all the metals at Control site was natural. Contamination factor analysis disclosed that Cd, Ni, Cr and Fe moderately contaminated dumpsite soils evaluated while Pb showed a considerable level of soil contamination. The Cdeg indicated that Uyo dumpsite soil recorded the highest degree of soil contamination while the lowest level of contamination was at Ikot Ekpene dumpsite soil. Cd recorded highest mobility potential in both dumpsite soils and Control while Cr was the least mobile element. Speciation results indicated that, Pb existed mostly in reducible fraction, Cd in acid extractable while Ni, Cr and Fe occurred mainly in the residual fraction.