ASSESSMENT OF BIOCONCENTRATION FACTOR FOR SELECTED HEAVY METALS IN Talinum triangulare (WATER LEAF) GROWN IN THE VICINITY OF AUTOMOBILE WORKSHOP IN OLUKU, BENIN CITY

Sensitive vegetables grown in heavy metals polluted soils tend to accumulate heavy metals which are harmful to the human body even at low concentrations. In this study, the bioconcentration factor (Transfer Factor) was used to assess the accumulation of some heavy metals in Talinum triangulare grown in the vicinity of an automobile workshop in Oluku, Benin City. Physical and chemical parameters found to affect the interactions and mobility of heavy metals in the soil mass were also examined. A pH of 6.17±0.2 was obtained for the topsoil while the middle and bottom soil samples were 5.93±0.4 and 6.00±0.1 respectively, The values of CEC obtained for top, middle, and bottom soil samples were 5.58±0.54, 4.56±0.11, and 3.65±0.14 meq/100g respectively. Soil samples were randomly collected from three depths of 0-10 cm, 10-20 cm, and 20-30 cm with the aid of a soil auger; and T. triangulare were collected within the soil sampling locations. The concentrations of heavy metal were evaluated through the use of atomic absorption spectrophotometer after the samples were subjected to tri-acid digestion techniques. Particle size analysis showed that the soil is a sandy loam texture. High Transfer factor values were ascertained for some metals but none was greater than one. Therefore T. triangulare cannot be considered a hyperaccumulator of heavy metals investigated in this study. However, all metals found in T. triangulare were highly significant (p<0.05), and higher than the permissible limits recommended by FAO/WHO/EC/CODEX. Consumption of T. triangulare harvested from the vicinity of automobile workshops should be highly discouraged to avoid public health hazards.