ABSTRACT
Environmental pollution in recent times of fast-tracked industrialized development around the globe demands consistent assessment of ecological matrices to enable the appraisal and evaluation of the probable risks to the environment. This study assessed the levels of heavy metal in sediment and fish (Gymnarchus niloticus) sample from Ossiomo River, South of Nigeria. A total of nine sediment samples and one fish sample were collected from November 2021 to January, 2022. Sediment samples such as pH, electrical conductivity (EC), total organic carbon (TOC), total nitrogen (N), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), total hydrocarbon content (THC), sand, silt and clay were analysed using various recommended routine laboratory analysis. Heavy metal concentrations in sediments were determined using Atomic Absorption Spectrophotometer.
The average mean concentration of physicochemical properties in sediments were 5.43±0.37 pH, 186.28±59.15 (uS/cm) EC, 1.41±0.94 % TOC, 0.29±0.17 % total Nitrogen, 63.09±19.36 mg/kg Ca, 26.48±15.77 mg/kg Mg, 11.73±1.61 mg/kg Na, 14.13±4.20 mg/kg K, 89.25±1.20 % sand, 5.03±1.81 % silt and 4.95±0.65 % clay respectively. Heavy metals concentrations in bottom sediments from Ossiomo River were 1137±760.55 mg/kg Fe, 6.83±1.24 mg/kg Cu, 28.94±11.93 mg/kg Zn, 0.14±0.06 mg/kg Cd, 5.80±5.27 mg/kg Pb, 9.02±3.80 mg/kg Mn, 4.30±1.04 mg/kg Cr respectively while total hydrocarbon content had an average mean value of 826.80±457.27 mg/kg. The result showed that the concentration of heavy metal were in the following decreasing order: Fe>Zn>Mn>Cu>Pb>Cr>Cd. Heavy metals in sediments exhibited positive and significant correlation with each other as well as with silt and clay.Five principal components were extracted in this study which accounted for 95.291% of the variance in the data set. The mean bioaccumulation of heavy metals in the liver, gills and muscle of Gymnarchus niloticus from Ossiomo River exists in the following order: Fe >Zn >Cu >Mn > Cr >Cd > Pb liver; Fe >Zn >Mn >Cu > Cr >Cd > Pb gills; and Zn >Fe > Mn >Cu > Cr muscle. Bioaccumulation factor (BAF) for Gymnarchus niloticus were > 1 for Cu, Zn, Cd, Mn and Cr in Gymnarchus niloticusacross the sampled stations.
These indices indicated anthropogenic sources of pollution and signify potential ecological risk. The government, civil society organization and all stakeholders should collectively create awareness programs among local people to educate and enlighten them about the problem of environmental pollution and their legal and social obligation to avert it.
