Evidence of heavy metal in soil, irrigation water and vegetable cultivated in peri‑urban area of Yaoundé-Cameroon

Abstract

Environmental pollution from anthropogenic activities is of global concern. The levels of heavy metal contamination were evaluated in the soil and irrigation water, and their transferability to the cultivated plant was appraised in the locality of Nkolbisson, Yaoundé-Cameroun. The levels of Zn, Cu, Cd, Ni, Pb, Cr, and Mn contamination were evaluated to determine the current status, possible source(s), bio-accumulation in food crops, the suitability of the water for irrigation purposes, and hence the probable health risk. The analysis of soils, waters, and crops (Corchorus olitorius and Lactuca sativa) samples has shown high levels of heavy metal contamination. Cd, Ni, and Cr concentrations in water samples (0.98, 2.230, and 2.635 mg/l) were above the threshold set by FAO for irrigation water. In agricultural soils, only the level of Mn (1013.090 mg/kg) contained in soil samples was above the European Union (EU) and the Canadian Council of Ministers for Environment (CCME) thresholds of toxicity. Except for Pb (0.361; 0.394 and 0.043; 0.041 mg/kg DM) and Mn (113.457; 123.341 and 173.667; 180.321 mg/kg DM), the concentration of heavy metals analysed in plant samples were above the standard values in the edible parts. Market gardening in this city presents risks due to the presence of heavy metals in soils and irrigation waters. Thus, market gardeners must be taking appropriate measures to avoid crop contamination. The bioconcentration and translocation factors have shown that Lactuca sativa can be used for phytoextraction of Zn, Cu and Cd whereas Corchorus olitorius can be used for phytomobilization of the same elements.