TROPHIC TRANSFER OF HEAVY METALS FROM DUMPSITE

ABSTRACT

Municipal waste contributes to heavy metal concentrations in soil, flora and fauna even at minimal amounts, and their transfer through the food web poses health risks to human. Here, the levels of six heavy metals in Amaranthus hybridus (Amaranthaceae) at Otofure dumpsite in Benin City was evaluated along with possible transfer through insect herbivory. Plant (root and shoot) and insects collected from the dumpsite and control site were analyzed. The overall findings showed that the heavy metals discovered in A. hybridus shoot that were sampled from the dumpsite were slightly or numerically higher but not statistically different in the control site (p-value > 0.05). For heavy metals absorbed by the root of A. hybridus, cadmium, manganese and zinc had elevated concentrations in the plants that grew at dumpsite compared to the control site which can be blamed on dumping of unsorted garbage in the dumpsite. Chromium and nickel levels, in particular, were above FAO/WHO recommendations in the shoot and root of A. hybridus, indicating possible human and ecological risks. Bioaccumulation of manganese was quite significant across selected insects groups (BAF > 1) indicating this metal was transferred along the food chain. Despite the data suggesting little bioaccumulation of other heavy metals by other insect groups, there is a risk that more toxic waste dumping would contaminate humans through the food chain or trophic transfer. In sum, this study calls for proper waste handling, education and legislation to prevent waste-related issues in the food chain.