Bioaccumulation of Single and Binary Applications of Cadmium and Zinc Contaminants in Okra (Abelmoschus esculentus (L.) Moench)

Abstract

The pathways of toxic exposure are mostly from air, water, soil and food. Of all these pathways, soil remains the principal pathway toxic wastes like dyes and heavy metals are discharged into the food chain. Soil contaminated with heavy metals is now a universal challenge leading to retardation in plant growth and yield. A study of single and binary application of zinc and cadmium metals concentration was compared at different levels in okra parts (fruit, leaf, stem and root). The samples under different levels of concentration of these metals were digested using a 1:4 mixture of concentrated HClO4 and HNO3. The acid digests were analyzed using the Flame Atomic Absorption Spectrophotometer. Contaminating the okra plant with increasing concentration of cadmium as contaminants 1, 2 and 3 shows a decrease in the growth area, percentage moisture content, fresh weight and root length which varies between 8.10–7.77cm2; 76.28–72.15%; 36.60–33.50g; 17.43–13.43cm respectively. Contaminants 4, 5 and 6 also show an inhibition of the growth area from 7.97cm2 to 5.34cm2; percentage moisture content from 73.64–69.97%; fresh weight from 47.00–35.60g; root length from 18.20–16.70cm respectively. On the contrary, the mixture of both metals as applied to contaminants 7–9 rather favor the growth area, percentage moisture content, fresh weight and root length of the okra plant from 7.97–8.55cm2; 70.38–74.41%; 30.45–38.25g; 14.34–17.90cm respectively. The root and fruit parts accumulated cadmium more than the stem and leafy parts. It was also observed that the leaf part has highest retention for zinc. The presence of Zn leads to decrease in the bioaccumulation of Cd in the case of binary application of metals. It is evident that estimated daily intakes of metals in okra fruit under all the contaminants examined were significantly lower than the recommended values. These measures include preventing the excessive application of pesticides and fertilizers for vegetable cultivation and continuous monitoring of different vegetables consumed.