Inventory of Herbaceous Species and Bioaccumulation of Heavy Metals in Their Various Parts: Case in the Urban Ecosystem of Ngaoundere, Cameroon

This study was carried out to inventory herbaceous species and to assess the bioaccumulation of heavy metals in these species. The ecosystem chosen was an area of the city of Ngaoundere (Cameroon) divided into three sites, namely a control site and two sites subject to heavy metal pollution. In order to compare the potential for bioaccumulation, two species were assessed. It shows that out of 19 herbaceous species present in the study area, five are very abundant in all three sites regardless of the degree of pollution. Concerning the bioaccumulation, the two herbaceous plants chosen do not absorb the same amounts of heavy metals. Indeed, the concentrations show that the concentration of cadmium, copper, iron, nickel and lead at all three sites is higher in Commellina benghalensis than in Ageratum conyzoides. The concentration of zinc at the control site and the hospital site is higher in C. benghalensis while at the prison site this concentration is higher in Ageratum A. conyzoides. The concentration of cadmium is higher in the leaves than in the other parts in both species. Copper is stored at the roots in both species. A. conyzoides, mainly accumulates iron in the roots and C. benghalensis, accumulates a significant concentration of Iron throughout the plant. A. conyzoides and C. benghalensis store nickel more in the roots than in the other parts. Regarding lead, the species studied store it more in the roots followed by the leaves and finally the stems. As for Zinc, A. conyzoïdes and C. benghalensis store it more in the roots than in the other parts. The bioaccumulation of these heavy metals in edible herbaceous plants could be a threat if these pollutants enter the human food chain.