An investigation on possible heavy metal occurrence in brassica oleracea l. on an agricultural land in Shashi, Bindura
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The possible occurrence of heavy metals: Zn, Cd, Cr, Ni, As and Fe in Brassica oleracea vegetable leaves was investigated. The study aimed to investigate whether the heavy metals concentrations in soil and plant leaves were contributing to the leaf chlorosis. Soil samples and B. oleracea vegetable samples were collected in polythene bags from agricultural land in Shashi, Bindura. The Strata A had affected B.oleracea leaves (chlorosis), B and C had normal vegetable leaves. Two vegetable gardens were used as replicates. The soil and B.oleracea samples were examined for Ni, Cd, Cr, Zn, As, Fe at Trojan Nickel Mine and soil pH, organic matter and soil moisture at FAES Laboratory. Data were analysed for significant variation and relationships using one way ANOVA and Pearson’s correlation in statistical software SPSS version 20. Results showed that, with the exception of Cr, the bio concentration factor of other heavy metals was low across all the strata. Low pH, organic matter content, soil moisture content were recorded in all the strata as well as the heavy metals occurrence in the soil and vegetable leaves.The declining trend for heavy metals bio-concentrations factor in the B. oleracea leaves was as follows: Cr>As>Zn>Fe>Ni>Cu. Mean heavy metals concentrations in the soil were as follows: Fe>Cu>Ni>Zn>As>Cr and in B. oleracea leaves there were: Fe>As>Cr>Zn>Cu>Ni. The heavy metals occurrence in both B. oleracea leaves and the soil were below the WHO permissible levels of heavy metals. It was concluded that the selected heavy metals (Cr, Zn, As, Fe, Ni and Cu) concentrations have less contribution to leaf chlorosis of the B. oleracea leaves. Future researches are should focus on the occurrence of other heavy metals such as Manganese, Lead, Mercury, Cadmium and other minerals and their contribution to the leaf chlorosis of B. oleracea leaves. An assessment should also be carried out on the bio-accumulation of these heavy metals in roots and stems of B. oleracea.