Distribution of Toxic Metals in Biota, Sediments and Water from a Polluted Mangrove Swamp in Rivers State

Abstract

Concentrations of Pb, Cd, and As were investigated in the tissues of mudskippers (Periophthalmus papilio), water, and sediments from Isaka-Bundu mangrove swamp in the Upper reach of Bonny Estuary, Niger Delta, Nigeria. The samples were collected from three stations every week for three months. The trace metals and physicochemical parameters were determined according to APHA 2000 methods. The concentration of trace metals by stations followed the order: station III (Dockyard) > station II (Bundu-Ama) > station I (Isaka). The trace metal distribution sequence in the fish, water and sediment according to their stations followed this sequence: Dockyard (Sediment = Pb > Cd > As; Water = Pb > Cd > As; Fish = Pb > As > Cd); Isaka (Sediment = Pb > Cd > As; Water = Pb > Cd > As; Fish = Pb > As > Cd); Bundu Ama (Sediment = Pb > Cd > As; Water = Pb > Cd > As; Fish = Pb = As > Cd). The overall, trace metal concentrations by samples followed this sequence; (Sediment = Pb > Cd > As; Water = Pb > Cd >As; and the mudskippers (P. papilio) = Pb > As > Cd) across the stations. The study revealed that all sampled sites in the Isaka-Bundu mangrove swamp had heavy metal values within Joint FEPA/WHO recommended biota load limits. High significant values of Pb and Cd were observed in sediment and water across the three stations, while tissue concentration of all three metals was relatively low and uniform. If proper measures are not taken to curb the excess discharges into the river given the activities in the catchment, the condition of the river will deteriorate badly and become a menace to its inhabitants and the host community which depends on it directly or indirectly.