Bioaccumulation of heavy metals by leafy vegetables grown with industrial effluents: A review

Abstract

Vegetables are capable of taking up and  accumulating heavy metals in their body. The concentrations of the metals increase as the soil available/background concentration increases as a result of human activities including discharge and dumping of industrial waste and effluents into environment. The aim of this review is to highlight the capability of the vegetables to take up and accumulate toxic heavy metals into their body as a result of industrial contamination of the soil and the water used for irrigation purpose and the impact of the metals on human and other organisms in the environment. For this review, available information on current publications, scientific journals, and articles were carefully used. Studies have shown that vegetables grown on a heavy metals contaminated soil accumulate higher amounts of metals than those grown on uncontaminated soils, because in most cases, they absorb the metals through the root. Sometimes, metals may be incorporated with some essential elements required by plants in water and soil. Certain species classified as hyper accumulators are vegetables (mostly leafy vegetables like; spinach, lettuce, and cabbage. Some of the factors that affect metals uptake in o plant tissue includes; bioavailability, nature and type of the metal, environmental factors including pH and the plant itself, as some studies have shown some plants to have high uptake capacity than others. High concentrations of Pb, Zn, and Cu were reported for vegetables grown in industrial areas. In most instances, the background concentration of the heavy metals in the soil may not exceed the permissible limit, however, the vegetables have the ability to absorb and accumulate the metals even above the permissible limit. These heavy metals are toxic and pose serious effect on human health and other organisms in the environment. Conclusively, vegetables plays an important role in the body because they provides some essential nutrients to the body as such, any contamination can pose a serious health threat. Moreover, prolonged exposure and consumption of these contaminated vegetables may lead cancer and death.

Key words: Accumulation, Biota, Effluent, Heavy metal, Toxic, and Vegetables.