Determination of elemental and nutrient composition of water, clam mantle and shell of the Volta clam (Galatea paradoxa) using neutron activation analysis

Abstract

The Volta clam Galatea paradoxa is a highly priced shellfish providing nutrition, jobs and poverty alleviation for the inhabitants of the lower Volta estuary. Clams are filter feeders straining particulate materials in the surrounding water, thus concentrating microorganisms and other metal elements in the gut and mantle which present possible health hazards. The elemental composition of the water, clam mantle, gut, shell, and bottom sediments were determined using Neutron Activation Analysis for the presence of Ca, Cl, Cu, Mg, Mn, V, Fe, Co, Br, Na and K. Proximate analysis of the mantle for the levels of protein, fat, carbohydrate, ash, wood fiber, phosphorus, free fatty acids and energy were carried out using the method of the Association of Official Analytical Chemists. The riverine water was laden with heavy metals V, Co, Cu, Mn, and Fe, as well as Al. These same metallic elements were detected in higher concentrations in the bottom sediments. Bioaccumulation factor (BAF) which is the measure of the distribution of heavy metals between water and biota (Clam mantle and gut), ranged from 2 to 145 times, depending on the type of contaminant. The clam meat contained high protein (15.3 ± 0.2%), no crude fiber, low fat content (1.80 ± 0.11%), fatty acids as oleic (25.2 ± 0.1%), energy (85.5 ± 0.21 kcal/100 g), carbohydrates (22.10 ± 0.03%), P (485 ± 1 mg/100 g), Ca (793 ± 75 mg/kg), Mg (860.3 ± 90.0 mg/kg). The high concentration of Ca (21,402.7 ± 797.0 mg/kg), Fe (18,071.2 ± 94.0 mg/kg), K (96 ± 14 mg/kg), Mg (540.8 ± 81.1 mg/kg), Na (4,570.0 ± 0.2 mg/kg) gives credence to the use of the shell for poultry feed mineral supplements, and in the emulsion paint manufacturing industry.