Trace metals bioaccumulation index and risk assessment in African giant land snail (Archachatina margenata) around University of Nigeria Nsukka sewage dumpsite, Enugu State Nigeria

The study investigates some selected trace metals bioaccumulation index and risk assessment in African giant land snail (Archachatina margenata) around University of Nigeria sewage dumpsite. Soil samples were collected at 30 cm depth with the aid of soil auger and snail samples were collected from the University of Nigeria sewage dumpsite and Etana snail farms served as control. The soil samples were collected at random and their physicochemical properties such as pH, total nitrogen, total phosphorus, organic matter, total carbon and exchangeable cations (i.e., K⁺, Mg²⁺ and Na⁺) were analyzed using a standard method. The heavy metals in soils and vegetables, Al, As, Cd, Cr, Cu, Hg, and Pb were analyzed using Flame Atomic Absorption Spectrometer (FAAS). The risk assessment from the consumption of snails in the study area was calculated using standard methods and formulae. The result showed a significantly different (p<0.05) in soil physicochemical properties between soil from the sewage dumpsite and Etana farm soil, except K⁺ which is not significant. The soil trace metal revealed that the mean concentrations of most of the trace metals were significantly (p < 0.05) higher at the sewage site compared to the control soil samples from the Etana snail farm. The concentration of trace metals (Al, As, Cd, Cr, Cu, Hg, and Pb) in snails from sewage dumpsite soil were 5.22, 3.85, 5.25, 3.42, 3.40, 3.60 and 2.88 mg/kg, while snails from Etana snail were 0.26, 0.33, 0.91, 0.28, 1.87, 0.06 and 0.11 mg/kg respectively. The concentration of trace metal in snail from sewage site were all greater than the maximum permissible limit of 0.5 (As), 2.0 (Cd), 0.3 (Cr), 0.04 (Cu), 3.60 (Hg) and 2.88 mg/kg (Pb) for snail given by FAO/WHO limits. The BAF of Cr, Cu, Hg, and Pb were greater than one (>1) in the test samples which indicates that snails are enriched with the trace metal from the soil (Bioaccumulators) while the control was all less than one. The result of DIM and HQ shows that sewage site snails have higher values of trace metals compared to the control farm. The Hazard Index (HI) shows that there is no harmful effect since the values obtained were below >1. But continuous consumption can accumulate in the food chain. This study showed that snails around the vicinity of sewage dumpsites were highly polluted with trace metals which can pose health risks.