Heavy Metal Concentration in Periwinkle - Tympanotomus fuscatus in Iko River Estuary, Nigeria

Heavy metals are intrinsic, natural constituents of our environment and are generally present in small amounts in natural aquatic environments. Humans may be contaminated by organic and inorganic pollutants associated with aquatic systems by consumption of contaminated aquatic foods from the environment. Relevant patents relating to heavy metal concentration in aquatic molluscs were reviewed. Gastropods; a promising bio-indicator and bio-monitoring subject, abound in brackish ecosystems in the Niger Delta, and are easily available for collection. Iko River Estuary, in Niger Delta zone, is one of the popular coastal areas of Nigeria where massive oil exploitation, exploration, production and refining processes take place.

The concentration of five heavy metals; Cadmium (Cd), Copper (Cu), Lead (Pb), Mercury (Hg) and Zinc (Zn) in the tissues of periwinkle; Typanotonus fuscatus, a gastropod bought from fishers fishing along the coast of Iko River Estuary was determined using UNICAM Solar Atomic Absorption Spectrophotometer 969 model for five months.

The results showed that Cd ranged from 68.83-130.5mg/kg with a mean value of 104.47±23.85mg/kg, Cu ranged from 34.9-73.62mg/kg with a mean value of 57.70±17.19mg/kg, Pb ranged between 54.27-102.54mg/kg with a mean value of 85.03±18.52mg/kg, Mercury ranged from 0.01-1.84mg/kg with a mean value of 0.41±0.80mg/kg and Zn ranged from 270.2-508.16mg/kg with a mean of 384.99±103.99mg/kg. The sequence of heavy metal concentration in the tissue of periwinkle was; Zn ˃ Cd ˃ Pb ˃ Cu ˃ Hg while the sequence of non-essential metals was Cd ˃ Pb ˃ Hg.

Except for Mercury, the mean concentration of the metals was above the maximum permissible limits recommended by relevant bodies and organizations. Hence, there is need for regular monitoring of heavy metal concentrations in this water body and the aquatic organism inhabitants because of the long term effects.