EFFECT OF DIFFERENT TYPES OF BIOCHAR ON HEAVY METAL BIOACCUMULATION BY LETTUCE AND HUMAN FOOD POISONING RISK

The objective of this study was to evaluate the impact of biochar application on the reduction of heavy metal contamination in soils and their bioaccumulation in lettuce. The study was carried out in Bobo-Dioulasso, Burkina Faso. Lettuce was grown in pots containing contaminated soil amended with three different types of biochar at three different doses. At maturity, the lettuce was harvested and the concentration of heavy metals in various organs was determined. The results showed that in terms of bioaccumulation in lettuce, the roots showed the highest accumulation of heavy metals, especially copper and zinc, with peak concentrations of 55.72 mg/kg for copper and 193.13 mg/kg for zinc. Cadmium was not detected in any part of the plant. The modelling results indicate that biochar application can effectively reduce the heavy metal hazard quotient, particularly in children and adolescents. To illustrate, a dose of 1 t/ha of chemically activated biochar was observed to reduce the hazard quotient for copper, lead and zinc in children by 0.06, 0.23 and 0.13 respectively. Significant reductions were also observed in adolescents and adults, with a maximum reduction of 0.39 for lead in adolescents. The chemically activated biotankswere found to be the most effective in reducing the above risk, followed by the physically activated biotanks. The study highlights the effectiveness of biochar, particularly in the context of reducing heavy metal contamination of crops and the associated risk of food poisoning, especially in vulnerable populations such as children.