Comparative Assessment of Heavy Metal Concentrations, Environmental Risks and Phytoremediation Potentials of R. racemosa and A. germinans in Mangroves of Niger Delta, Nigeria

The concentrations of As, Pb, Zn, Cu, Ni, Cr, V, Sr, Y, Nb, Zr, Cl, TS, TiO2, MnO, CaO and P2O5 in the mangrove sediments relative to concentrations in R. racemosa and A. germinans samples from Ogbogoro and Isaka in Niger Delta, Nigeria were assessed. A total of 4 core sediment, 6 R. racemosa and 4 A. germinans samples were collected through simple random sampling. Two core sediment samples of 10 cm depth and three R. racemosa leave, stem and root samples were collected from each of the sampled locations. However, one and three A. germinans leave, stem and root samples were collected from Ogbogoro and Isaka respectively. All the samples were oven dried, powdered, made into briquettes and analyzed using XRF. The results indicated contrasting heavy metal concentrations in the sediments, R. racemosa and A. germinans samples. Sr, Zr and CaO had higher concentrations in R. racemosa relative to A. germinans while Zn, Cu, Ni, Nb, Cl and TS are comparatively more concentrated in A. germinans than in R. racemosa. However, As, Pb, Y and P2O5 have similar concentrations in both mangrove species. Cr, V and TiO2 were not detected in both R. racemosa and A. germinans while MnO was detected in R. racemosa but not detected in A. germinans. Similarity was observed in metal concentrations in the leaves, stems and roots of R. racemosa and A. germinans. The ecological risks of metal concentrations in both plants were determined using Contamination Factor (CF) and Pollution Load Index (PLI) while the phytoremediation potentials of the plants were assessed using Bio-concentration Factor (BCF) and Bio-translocation Factor (BTF). R. racemosa and A. germinans were found to be moderately contaminated though the PLI indicated that they are unpolluted. R. racemosa and A. germinans were found to have phytoremediation capacities in Cu, Ni, Sr, Zr, Cl, TS, MnO, CaO, P2O5 and Zn, Cu, Sr, Zr, CaO, P2O5 respectively.