Environmental pollution is assuming frightening dimensions in many parts of
the world. This is not excluding Niger-Delta region of Nigeria where most of the country’s oil
and gas are sourced with attendant production of noxious substances as byproducts/
residues/waste. Many of these noxious substances have been noted to be removable
from polluted environment through proper application of phytoremediation techniques,
particularly using native plant species. Consequently, this research was conceived to evaluate
potentials for phytomediation by native red mangrove tree (
Rhizophora racemosa
G.F.W.
Meyer). This was carried out by evaluating the presence of heavy metals ions and their bioconcentration
levels in the samples of root and wood tissues axially along the stem of this
tree. The sorrounding soil and water were also sampled and evaluated for presence and
concentration of these metal ions in comparison with those for the sampled plant tissues. All
the samples were sourced from a mangrove forest in Okrika, Rivers State, Nigeria. The
samples from the root, butt, 50% and 90% bole length were oven-dried at 60±5°C to constant
weight, pulverised and heated with trioxonitrate (v) acid to achieve total dissolution before
subjecting them to atomic absorption spectroscopy (AAS). Similarly, samples from
sorrouding soil were dried at 35±2°C to constant weight, crushed and sieved using a ≤ 2mm
mesh before performing metal extraction and detection using AAS while water samples were
also subjected to AAS for heavy metal analyses, in line with appropriate standard methods.
The data obtained were statistically analysed using basic descriptive tools, Analyses of
Variance and Fishers’ Least Significant Difference (P < 0.05). Outcomes of these statistical
analyses showed that, in terms of bio-concentration values, the evaluated metal ions that
include Fe, Cu, Mn, Cd, Pb, Ni and Cr were more in the root than the surrounding soil and
water. The bio-concentration trends, for the metal ions, also progressively declined from the
root towards the crown of the trees. The bio-concentration distribution in all the tree sections
showed an inconsistent pattern with Fe ions having higher bio-concentration. In addition, Cr,
Ni, Pd and Cu also inconsistently followed Fe in terms of bio-concentration level.
