Temporal Survey of Heavy Metal Loads in Surface Water, Sediments and Shrimps from Iko River Estuary, Eastern Obolo L.G.A, Nigeria

Abstract

Aims: This work aimed at providing pieces of information on the trend and levels of heavy metals in shrimp, surface water and sediment from Iko river estuary, Eastern Obolo, South-South Nigeria.
 Study Design: The study area was demarcated into three stations for sampling. The sampling stations were subjectively categorized.
 Place and Duration of Study: The study which was carried out in Iko river estuary, Eastern Obolo, South-South Nigeria lasted for 12 months.
 Methodology: Samples were collected once a month for 12 months in a consecutive manner and analyzed using standard methods. 
 Results: When compared to water and shrimps, sediments contained the highest concentration of heavy metals during the study period. Contrarily, water had the highest concentration (1.50 Mg/L) of Cd, compared to 0.85 Mg/Kg in sediment and 0.27 Mg/Kg in shrimps. Levels of Lead (Pb) in the study samples followed a similar trend like that of Cd. Zinc also followed a contrary pattern with shrimps having the highest concentration (65.35 Mg/L). Of all the metals studied, iron (Fe) was found to be the most abundant heavy metal in Iko River Estuary. Although levels of Fe were generally high in all the samples studied, concentration in sediment (113.99 Mg/Kg) far outweighed the concentrations in shrimps (227.11 Mg/Kg) and in water (184.35 Mg/L). These levels of heavy metals determined in the water, sediment and shrimps showed variations during the wet and dry seasons.
 Conclusion: The values were higher than the recommended limits. It can therefore be concluded that Iko River Estuary was always laden with heavy metals notwithstanding the season of the year. Accumulation of these metals in shrimps also indicates that sea foods from this river may not be suitable for consumption.