Ecological Assessment for Trace Metal Pollution in a Freshwater Ecosystem


Heavy metals in the aquatic environment is of great ecological importance; hence, the study was carried out to evaluate the presence and effects of heavy metals on the water column, fish and sediment composition of Anambra River in July, 2011 and February, 2012 which covered both wet and dry season. The results of the physico- chemical properties showed significant variations (P<0.05) which occurred in DO and conductivity over the sampling seasons on different locations. pH, temperature and salinity showed seasonal difference at P<0.05 in different locations studied.

There was no seasonal difference at P>0.05 among the heavy metal concentrations detected in sediment. Post Hoc test also showed no statistical variation (P>0.05) over the five locations: namely Enugu Otu, Ezi - Agulu Otu, Otuocha, Otu Nsugbe and Ukwuibili. There was stable relative non-statistical variations among the heavy metal concentration in the water column but numerical differences demonstrated variability (Otu-Nsugbe > Ezi Agulu Otu > Ukwuibili > Enugu Otu > Otuocha.
For the fish species caught both in the rainy and dry season, Clarias gariepinus and Mugil cephalus showed higher (P <0.05) concentrations of Zn in dry than rainy season, while Heterotis niloticus showed higher (P<0.05) concentrations of Zn in rainy than dry season. The highest concentrations of heavy metals were detected in the sediment followed by the fish and finally the water column in a decreasing order of concentrations.
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