Health risk assessment of heavy metals (Cu, Zn, and Mn) in wild oat grown in soils amended with sediment dredged from the Joumine Dam in Bizerte, Tunisia

Abstract

AbstractThe Joumine Dam located in northern Tunisia has lost more than 20% of its initial storage capacity due to sedimentation, meaning that sediment management is necessary. The sediments at the reservoir bottom act as a sink for nutrients and chemicals originating from the upper agricultural lands and take the form of suspended particles. We proposed that the dredged sediments could be used to amend arid to semiarid soils, as this would partially cover the financial burden of dredging works and reduce the volume of these deposits. However, to check the feasibility of using the sediments as a fertilizer, it was necessary to assess the potential health risks from contaminants in the sediments. Therefore, the present study aimed to evaluate the human health risk (i.e., the hazard quotient, HQ) from heavy metals consumed due to the ingestion of Bromus ramosus (wild oat) grown in soil amended with the Joumine Dam sediments. Plant growth was monitored in macrocosm (amendment rate of 1.17%) and microcosm (amendment rate ≤ 10%) bioassays to elucidate the metal concentrations in roots, stems, leaves, and seeds. Zn, Cu, and Mn concentrations were analyzed in the plants grown in the macrocosm experiments, while the follow-up was only performed for Zn in the plants grown in the microcosm experiments. The human exposure to soil pollutants (HESP) evaluation model was adopted to evaluate the health risk (HQ) to humans through direct and indirect oral exposure to heavy metals in wild oat. At the macrocosm scale, Cu was found to be the main source of risk (HQ = 1.86) to children. At the microcosm scale, utilization of the sediment reduced the mobility and bioavailability of copper in the soil, thus decreasing the potential health risk from this metal. Graphic abstract