Assessment of Physicochemical Characteristics and Heavy Metal Concentration in Soils and Plants in Selected Refuse Dumpsites within Nkwerre L.G.A., of Imo State, Southeast Nigeria

Abstract

Environmental contamination by heavy metals as a result of unregulated disposal of wastes is a serious challenge all over the world. Early detection and remediation of heavy metals in soil and plants will ameliorate serious potential threats posed to human health and other components of the ecosystem. This study was conducted to evaluate the physicochemical characteristics and selected heavy metal concentration in soils and edible plant at three different refuse dumpsites in Nkwerre Local Government Area of Imo State and compared with the permissible limits specified by WHO/FAO standards. Soil samples were collected from a depth of 0 – 20 cm using a soil auger while plant samples were collected from same source as the soil. Samples were collected from an area with no history of dumpsites which served as control. Standard analytical procedures were used for physicochemical parameters while Atomic Absorption Spectrophotometer (AAS) was used for the heavy metals analysis. Results showed significant (p>0.05) higher changes in the soil physicochemical properties relative to the control. Mean heavy metal concentration in soil from site A were: 239.158±26.57 (Fe); 0.080±0.008 (Cd); 0.012±0.001 (Ni); 1.040±0.12 (Mn); 0.899±0.10 (Pb); and 14.123±1.57 (Zn); site B were: 24.854±2.76 (Fe); 0.069±0.008 (Cd); 0.056±0.006 (Ni); 1.163±0.13 (Mn); 0.133±0.02 (Pb); and 16.004±1.78 (Zn) while that of site C were: 15.536±1.73 (Fe); 0.069±0.09 (Cd); 0.333±0.04 (Mn); 0.767±0.09 (Pb); 3.097±0.34 (Zn). The values of all the metals analyzed for samples from dumpsites were higher than those from the control but were below values recommended by the WHO/FAO except for Fe and Zn in some sites. Talinum triangulare showed bioaccumulation factor (BF) and transfer factor (TF) greater than 1 for Fe, Cd, Mn, Pb, and Zn indicating that the plant can be effectively used for phytoremediation. A strong positive correlation was observed for all the metals studied, Fe (r = 0.981), Cd (r = 0.720), Ni (r = 0.823), As (r =0.945), Mn (r = 0.830), Pb (r = 0.832) and Zn (r = 0.913) implying that the metal level in the refuse dumpsite soil is the major factor responsible for the heavy metal contents in the plant species studied. Regular monitoring of heavy metals in refuse dumpsite soil is recommended to forestall excessive accrual in the food chain.