Translocation of Trace Metals in Vegetable Crops Grown on Irrigated Soil along Mada River, Nasarawa State, Nigeria

Trace metals play an important role in the metabolic pathways during the growth and development of plants, when available in appreciable concentration. Pepper and okra vegetable crops were collected from irrigated farmlands along Mada River and separated into roots, stems, leaves and fruits. Concentrations of cadmium, copper, chromium, iron, nickel, lead, zinc and manganese were analyzed using atomic absorption spectrometry. Biological concentration factors (BCF), transfer factor (TF) and, biological accumulation coefficient (BAC) were calculated for assessment of mobility of trace metals from soilroot, root-shoot and soil-shoot, respectively. Mobility index (MI) was also calculated for roots-stems, stems-leaves and stems-fruits. The results showed concentration dependent variables of heavy metal levels between vegetables. Accumulation gradient of each crop component varies according to nature of the vegetable. MI of metals among components in okra exceeded in roots-stems and the least in stems-fruits. MI for the stems-leaves and roots-stems in pepper were the highest and lowest, respectively. Cr was the most mobile metal and Ni the least. TF and BAC values for Cd in okra and pepper were high. TF, BAC and BCF values for trace metals in okra at farm B were higher than in pepper.