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Paper Number: 32
Barth
N. Ekwueme; Uwem N. Etukudo; Onyekachi A. Nwakwue; Idara U. Imaikop;
Nyeti I. Essien and Deborah E. Mfon
1Department
of Geology, University of Calabar, P. O. Box 3651 Unical, P. O. Calabar,
Cross River State, Nigeria. Email: bachudo@yahoo.com
This study was initiated to evaluate the spatial distribution of
heavy metals in streams and river sediments in parts of Akpabuyo, Cross
River State, Nigeria. Surficial streams and river sediment samples were
taken from 10 sampling stations and analysed for availability of Fe, Zn,
Mn, Cr, Ni, Co, Cu, Cd, and Pb. The concentrations of the heavy metals
were found to be in the ranges (mg/kg): Fe (144.45 - 564.76), Zn (19.56
- 44.36), Mn (11.93 - 30.06), Cr (9.75 - 27.68), Ni (6.56 - 18.04), Co
(5.36 - 56.41), Cu (3.35 - 6.80), Cd (1.18 - 2.91), and Pb (1.34 -
4.41). The order of concentration in most of the streams and river
sediments were found to be: Fe > Zn > Mn > Cr > Ni > Co
> Cu > Pb > Cd. The sediment quality indexes used were
Geo-accumulation index, contamination factor and pollution load index.
The Geo-accumulation index values for Cd ranged between 1.4 and 2.7,
indicating moderate to severe contamination and that of Co in Ekpene
Tete was 0.985, implying moderate contamination. The contamination
factor value for Co in Ekpene Tete was 2.969, indicating moderate
contamination factor, while that of Cd in the entire sampling station
ranged between 3.953 and 9.717, implying considerable to very high
contamination factor. Also, the pollution load index values indicate
that these metals ranged around background levels, with exception of Cd
at all sampling stations, indicating pollution. Furthermore, comparison
of the heavy metals with other studies showed that the concentration of
Cd in the study area was higher. The high concentration of Cd in the
study area is possibly due to weathering of rocks and minerals in the
nearby Oban Massif and Calabar Flank and farming activities in the area.
The toxic level of Cd has negative implications for the environment and
the food chain since the area is agrarian.
