Pollution Effects of Quarrying on Soil Health and Nutritional Composition of Selected Vegetables

The pollution effects of quarrying on soil health and nutritional composition of Eggplant (Solanum melongena) and African Spinach (Amaranthus hybridus) were investigated. Soil samples were analyzed for physicochemical indices (Conductivity, pH, TOC, NO3, PO4 and Sulphate) and heavy metals (Zn, Cr, Ni, Pb, Cd, Mg, Ca, Mn, and Na) using standard analytical methods. Proximate composition and the level of heavy metals in Eggplant and African Spinach samples were assessed using Atomic Absorption Spectrometry (AAS). Total Organic Carbon (TOC) values in soil ranged from 1.50 ± 1.31% to 3.50 ± 0.49%. Values obtained for soil NO3 were significantly higher than standards set by WHO and USDA, and ranged from 14.47 ± 0.82mg/kg to 18.86 ± 0.86mg/kg. Analytical results revealed high concentration of Zn and Mn in soil samples from the three quarry sites, when compared to recommended standards. Values for Zn ranged from 14.20 ± 1.21mg/kg to 20.81 ±0.35mg/kg. Proximate analysis of Eggplant and African Spinach cultivated within the quarry environs showed high levels of ash, carbohydrate, protein and dietary fibre. However, the concentration of Cr and Cd in Eggplant exceeded recommended levels. Similarly, Zn, Cr, Mg, Na and Ca in African Spinach also exceeded established standards. Overall, results obtained revealed deterioration of soil quality near the quarries, with significantly high levels of Zn and Mn. These findings suggest that quarrying within the study area has detrimental effects on soil health and suitability of cultivated edible vegetables for human consumption due to possible accumulation of toxic contaminants.