mpact of contaminated water and soil by copper and zinc on market garden products in Cotonou (Benin)

Abstract

Agriculture represents a highlight activity in Benin but this activity faced many environmental issues. The main objective of this study is to determine physicochemical parameters of the water used in market gardening in Fidjrossè and concentrations of copper and zinc in the watering waters, soils and plants grown. This study is initiated to assess the level of copper and zinc pollution of the most consumed leaf vegetables. For this purpose, the total metal contents in irrigation water, soil and in the main market garden crops such as big nightshade and amaranth were analyzed. To more assess the contamination, the bioaccumation factors were also calculated. The results of these analyze show a contamination of vegetables in metals. For copper, the values range from 13.06 mg/kg to 17.89 mg/kg for large nightshade and from 9.90 mg/kg to 11.58 mg/kg for amaranth. For zinc, these values range from 27.83 mg/kg to 87.69 mg/kg for the large nightshade and from 5.94 mg/kg to 33.73 mg/kg for amaranth. These values are well above the maximum allowable standard of 3.3 mg/kg for copper and 5 mg/kg for zinc. The contamination is linked to the presence of these metals in the water and in the soil. The bioaccumulation factors ofmetals in relation to water and soil revealed that these metals are more available in water than in soil. It is therefore recommend improving the agricultural practices to clean up the environment in order to limit water and soil pollution and water and consequently ensure a good quality of vegetable crops