Assessment of the Levels of Some Essential Metals in Selected Vegetables Grown on Contaminated Soil Using AAS and UV-Spectrophotometry

Abstract

Excessive nutrient supply or deficiency in plants poses a major challenge to physiological and metabolic development, both of which are governed by rates of essential metal uptake. This study was conducted to determine the level of uptake of different essential metals from contaminated soils by selected vegetables such as tomato, pepper, garlic, carrot and spinach: Amaranthus hybridus and Celosia argentea. The amounts of essential metals (Zn, Mg, Mn and Mo) absorbed in the various parts of the vegetables were determined using Atomic Absorption Spectrophotometry after dry ashing at 550 °C. Molybdenum determination was carried out using UV-Spectrophotometry after ashing. From the results obtained, it was observed that the rate of metal uptake varied across and within plant parts. Celosia argentea roots, carrot leaves, tomato leaves, and garlic roots displayed the highest level of Mn (96.67 ± 0.03), Zn (67.11 ± 0.16), Mg (188.32 ± 0.22), and Mo (3.74 ± 0.001) uptake respectively. In contrast, the lowest level of metal uptake was recorded in Celosia argentea leaves (Mo: 0.71 ± 0.01), tomato roots (Zn: 5.67 ± 0.04), garlic leaves (Mg: 13.81 ± 0.04), and garlic roots (Mn: 0.94 ± 0.004). Our findings are that Celosia argentea and carrot plants respectively displayed the highest and lowest essential metals uptake. The difference in essential metal uptake by respective plants may be attributed to the increasing level of soil contamination, as well as the antagonistic and synergistic effects of metals. From this study, results indicate that metal bioavailability varies widely from element to element and according to element type and plant part.