Determination of heavy metals in soil and vegetable products in Benin

Abstract

Market gardening in towns and peri-urban localities is not without consequence on the quality of the market garden products which are cultivated there. This study aims to evaluate the quality of market garden produce consumed in Benin in order to better understand the risks to human health. Heavy metals (Pb, Cu and Zn) were determined by atomic absorption spectrophotometry in soil and fresh and cooked vegetable crops. The study showed that the soil of the various vegetable crops is contaminated by heavy metals (Pb: 0.028 to 2.235 mg/kg, Cu: 0.037 mg/kg to 0.264 mg/kg, Zn: 0.613 to 3.234 mg/kg) and the compost used for its amendment too (Pb: 0.224 mg/kg, Cu: 0.419 mg/kg and Zn: 1.717 mg/kg). The vegetable crops analyzed are also contaminated by heavy metals (Pb: 0.009 to 4.124 mg/kg, Cu: 0.073 mg/kg to 2.146 mg/kg, Zn: 0.573 to 14.12 mg/kg) with bioconcentration factors ranging from more than 4 for Brassica oleracea and 8 for Vernonia amygdalina which are the most contaminated. However, cooking has resulted in a significant reduction in heavy metal contents, which reduces the health risk for the consumer. A vigilance of the population and a variation of the food are then important to guarantee a better health. It is planned to continue research on other vegetable crops and chemical pollutants