Hepatic and renal concentrations of 10 trace elements in crocodiles (Crocodylus niloticus) in the Kafue and Luangwa rivers in Zambia

Hepatic and renal concentrations of the elements arsenic, cadmium, cobalt, copper, lead, manganese, mercury, molybdenum, selenium and zinc were determined in samples collected from four crocodiles from the Kafue River, Kafue National Park and five crocodiles from the Luangwa River, Luangwa National Park, Zambia. The concentrations of the essential elements were similar to those reported in other vertebrates. Arsenic and cadmium concentrations were low (medians below 0.05 Ag As/g and below 0.16 Ag Cd/g, wet wt.). Mercury and lead concentrations were several orders of magnitude higher (medians up to 3.7 Ag Hg/g, and up to 8.7 Ag Pb/g, all wet wt.) than in hippopotami from the same rivers, probably as a result of food-chain biomagnification. Judging by the results obtained in this study, pollution from the mining activity around the Kafue River drainage area in the Copperbelt region has not significantly influenced the trace element concentrations in tissues of the crocodiles in the Kafue National Park. The trace element concentrations measured may serve as reference values in future studies on crocodilians.