SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

EKPENYONG, E.O
OKOYE, P.A.C
AJIWE, A.I.E

ABSTRACT:

Heavy metal levels in fishes are of vital concern to man, as they have direct link to human health and welfare. Consequently, there is need to assess pollutant levels of surface water, sediments and fishes from Mbo River System, Akwa Ibom State, Nigeria. Physicochemical analysis of water and sediments were determined by American Water Works Association (AWWA) standard Method. Levels of interaction between water parameters were subjected to correlation analysis. Microbial assay were by membrane filtration method; sediment texture and particle grain size by Bouyocous hydrometer test. Heavy metals in water, sediments and fish organs were determined using atomic absorption spectrophotometetric method (AAS). Heavy metals due to dietary intake through fishes were calculated using Hazard quotient (HQ) model. Results showed that in water, percentage prevalence of bacteria and fungi isolates were very high. Temperature, EC, COD, Fe, Pb, Cd and Ni were above WHO standards. COD and Alkalinity (r = 990**), temperature and TDS (r = - .996**) of water showed positive and negative correlation respectively. Physicochemical parameters eigen value 11.4 – 21.1, total variance 45.15 – 76.17% of water were the major influencing factor. In sediment, sand-grain (0.2-0.8mm), sand (61.80-83.10%), silt (5.90-16%), clay (11.0-26.28%) were moderate. Nutrients, temperature, pH and conductivity values of sediment were lower than their corresponding values for water. Co, Cd, Ni and V in sediment recorded higher values above ISQG standard and was influenced by strong metallic presence.
The levels of Fe, Pb, Cd, Ni and V obtained in the organs of fishes are more than tolerable limits of FAO. Bioaccumulation of heavy metals in fish organs followed the pattern; gill>Liver>Intestine>Kidney>Muscles whereas trend of heavy metal concentration in fishes were Zn>Cu>Fe>Pb>Ni>V>Cr>Co = Mn. Ni and Pb from sediment and fish, Cr and Ni from water and Fish showed strong positive association while Pb and Cu from water and fish showed poor correlation. Ingestion of Pb, V, Fe, Cd from sediment into the fish organs followed the pattern Xenomystus nigri organs>ilisha africanus organs>pseudolithus organs. All other heavy metals recorded hazard quotient less than 1 except Cd in all the fishes. Mbo River system is therefore polluted based on above results. Thus, routine monitoring of anthropogenic activities and provision of wastes disposal facilities is expected. Ban by legislation on direct defecation into rivers, unauthorized sand excavation, discharge of metal containing wastes and citing of cottage industries closer to riverside are recommended.