Abstract
Mining and smelting of metal ores are among the major anthropogenic activities contributing to environmental pollution, particularly through the release of toxic metals into surrounding soils. This study investigates the extent, intensity, and spatial distribution of heavy metal contamination in soils surrounding the Non-Ferrous Metal Smelter (KCM–Plovdiv) in southern Bulgaria. Total concentrations of Pb, Zn, and Cd were measured and compared with national and international soil quality standards, including the Bulgarian Regulation No. 3, WHO reference values, and the Dutch Maximum Allowable Concentrations (MAC) and Intervention Concentrations (IC). Several contamination indices were applied, including the geoaccumulation index (Igeo), contamination factor (CF), pollution load index (PLI), and Nemerow index (NPI).
The results revealed extremely high metal concentrations, with maximum values of 28,162 mg/kg for Pb, 10,596 mg/kg for Zn, and 528.8 mg/kg for Cd. A pronounced spatial gradient was observed, with the highest contamination within 500 m of the smelter chimney. Contamination was largely restricted to the topsoil (0–20 cm), reflecting limited vertical mobility of Pb and Cd. Integrated indices (PLI, NPI) confirmed severe to extreme pollution across most of the study area, with NPI values exceeding 190 at several hotspots. These findings demonstrate large-scale, long-term heavy metal pollution and emphasize the need for remediation and continuous monitoring.
Keywords: cadmium, pollution indices, soil contamination, lead, zinc, smelter