Heavy metal contamination of some leafy vegetables growing within Ibadan metropolis, South-western Nigeria.

Abstract

Most vegetable farms in urban areas of Nigeria are located by the roadside, where environment is heavily polluted with heavymetal-laden exhaust. Within Ibadan metropolis, Am aran th u s cruentus, Celosia argentea and Corchorus olitorius are commonly grown all the year round. Accumulation of lead (Pb) and cadmium (Cd) in the three leafy vegetable samples in three different traffic density areas was investigated using atomic absorption spectrophotometric technique. Results revealed that the highest concentrations of Pb and Cd in vegetables were present in samples taken from the high traffic density area. Lead and cadmium concentrations varied among vegetable types. The unwashed leaves of Am a ran th u s had the highest lead (157.69±21.52pg/g) and cadmium (138.76±26.92pg/g) concentrations. The amount of heavy metal removed by washing the plant materials in distilled water was in the range of 6.93 to 53.27% (mean=28.37%) for lead and 19.82 to 72.64% (mean=44.64%) for cadmium. This may imply that in terms of deposition on the plants there was more of cadmium than lead and in term of assimilation into the tissues there was more of lead than cadmium. The implication of continuous ingestion of these contaminated vegetables for bioaccumulation and bio-magnification of the heavy metals in the digestive system of vegetable consumers is discussed.