ASSESSMENT OF POLLUTION STATUS OF IMO RIVER, SOUTH EASTERN NIGERIA

ABSTRACT

Globally the environment has been over the years faced with the challenge natural and anthropo- genic waste management which affects water, sediment, fish and humans. These issues necessi- tated this work aimed at assessing the pollution status of upper part of Imo River, South Eastern Nigeria. This work was carried out using three parameters: physico-chemical, heavy metals con- centration and PAHs analysis in three media namely: water, sediment and biota (fish). Triplicate batches of the samples were taken from three sampling points along the river coast and the physi- cochemical parameters analyzed in-situ and in the laboratory using gravimetric, titrimetric and spectrophotometric methods. The concentrations of heavy metals (Fe, Cd, Ni, Zn, Pb, Cu and V) in water, sediment and muscle of 2 fish species (Tilapia and Cat fish) from Imo River were ana- lyzed using atomic absorption spectrophotometer. The results obtained were compared with both local and global standards for water, fish and sediments. The sixteen (16) priority polycyclic aro- matic hydrocarbon (PAHs) were also investigated in water, sediment and fish (Tilapia and Cat fish) using gas chromatography coupled with mass spectrophotomer(GC-MS). Carcinogenic and non-carcinogenic risk models, Pearson correlation multivariate analysis of variance (MANOVA) were used to analyze the inter-relationship amongst water, sediment and fish. Seasonal variation and correlation matrix (ANOVA) of heavy metals were analyzed. The results showed that most of the parameters analyzed fall within the permissible limit except turbidity, conductivity, biochem- ical oxygen demand (BOD) and phosphate with mean values of 14.50NTU, 128µs/cm, 6.54mg/L and 0.5mg/L respectively which exceeded WHO and USEPA permissible limits of 5NTU, 100µs/cm, 5mg/L and 0.1mg/L. Sand was predominant in sediments with mean particle size dis- tribution of 60.11% sand, 26.27% silt, 13.62% clay. The mean concentration of heavy metals in water from Imo River was Fe (0.019), Cd (0.0087). Pd (0.0188), Ni (0.149), Zn (0.0915), Cu (0.02)

and V (0.017) while for sediment the values were Fe (1.005), Cd (0.0164). Pd (0.0575), Ni (0.055), Zn (3.185), Cu (0.99) and V (0.048) mg/kg. The mean values of heavy metals in the two fish samples were 3.925, 0.000415, 0.041, 0.055, 0.3615, 0.055, ND in Tilapia and 5.925, 0.057, 0.05,

0.0525, 0.685, 0.15 and ND in cat fish for Fe, Cd, Ni, Zn, Pb, Cu and V respectively. The mean values of LMW-PAHs in water, sediments and fishes were 0.0198, 0.1095 and 0.067 respectively while the mean values of HMW- PAHs in water, sediments and fishes were 0.072, 0.0128 and

0.006 respectively. Some of the PAHs concentration measured were within the WHO recom- mended limits while some PAHs such as naphthalene (0.0648), chrysene (0.0852), benzo (a) py- rene (0.300), and indeno (1, 2, 3, cd) pyrene (0.015), measured exceeded the recommended limit of (0.014), (0.000218), (0.005), and (0.0015) respectively. The cancer risk indices obtained from this study ranged from 10-2 to 10-4. The questionnaire administered on the pollution status of Imo River showed no evidence of cholera outbreak but gastroenteritis The results obtained from this study showed that Imo River was moderately polluted at the time of this investigation.