Metals in the Mix: Assessing Trace Metal Contamination in Composted Soil and Cultivated Crops from Dumpsites

Abstract

In many agricultural settings, the high cost of inorganic fertilizers has led farmers to resort to using composted soil from large dumpsites for soil amendment, in some cases, farmers even level smaller dumpsites and utilize the land for crop cultivation. This study investigated the concentrations of trace metals (Cd, Cr, Cu, Mn, Ni, Fe, Pb, Zn) in dumpsite compost, soil for cultivation, maize plants, and spinach vegetables, comparing them against the limits established by Directive 2014/118/EU. The results revealed significant variations in trace metal levels across the different samples analysed. Dumpsite compost exhibited elevated concentrations of Cd (6.00 mg/kg), Cr (89.00 mg/kg), Cu (21.00 mg/kg), Mn (101.00 mg/kg), Ni (17.12 mg/kg), Fe (1570.02 mg/kg), Pb (29.31 mg/kg), and Zn (315.18 mg/kg), surpassing the EU limits for Cd, Cu, Ni, Pb, and Zn. Conversely, soil for cultivation demonstrated lower trace metal concentrations, with Cd (0.40 mg/kg), Cr (21.31 mg/kg), Cu (1.72 mg/kg), Mn (12.98 mg/kg), Ni (2.43 mg/kg), Fe (520.11 mg/kg), Pb (0.98 mg/kg), and Zn (67.31 mg/kg), still exceeding EU limits for Cd, Cr, Mn, Ni, and Zn. Maize plants and spinach vegetables showed varying levels of trace metals, with concentrations generally lower than those in dumpsite compost but still exceeding EU limits for several metals. The calculated index values indicated significant contamination in all samples, with values less than 1. The metal uptake by plants, as indicated by the index values, followed the order Cd > Pb > Cu > Ni > Cr > Zn > Fe > Mn. This study underscores the potential health risks associated with consuming crops grown in contaminated soil and highlights the importance of continuous monitoring and remediation efforts to ensure food safety and environmental health.