Assessment of copper, cobalt and zinc contaminations in soils and plants of industrial area in Esfahan city (in Iran)

The infiltration of heavy metals into soils through steel plant production processes is one of the most important soil pollution sources. The aim of this study was to determine copper (Cu), cobalt (Co), and zinc (Zn) concentrations in soil and plant shoots around the Esfahan steel company (ESC). In this study, we separated 17 zones based on soil maps and marked 54 points for soil sampling. Samples were collected from each point at 0–5, 5–10, 10–20 and 20–40 cm depths and DTPA-extractable concentrations of Cu, Co, and Zn were determined. Also 162 plant samples from shoots of 13 main plant species were collected and the concentrations of Cu, Co, and Zn were determined. The results showed that the maximum concentrations of Cu, Co, and Zn were 9.2, 2.4, and 10 mg kg⁻¹ soil at the depth of 0–5 cm. A comparison of the heavy metal contents at different levels showed Cu, Co, and Zn contamination in soil profile, especially in topsoil (0–20 cm) that was mainly caused by anthropogenic activities. Also significant correlations existed between Cu, Co, and Zn concentrations. The maximum concentrations of Cu in shoots of Triticum vulgare, Medicago sativa, Amygdalus scoparia and Oryza sativa were 21.8, 21.2, 21, and 20.3 mg kg⁻¹dry matter that were higher than the standard levels of Cu in plant dry matter. The maximum concentrations of Co in shoots of Medicago sativa, Vitis vinifera, Euphorbia spp., and Tamarix spp. were 12.7, 11.3, 10.3, and 10.2 mg kg⁻¹ dry matter that were extremely higher than the standard levels of Co in plant dry matter, but the maximum concentration of Zn in shoot of Medicago sativa was 51.7 mg kg⁻¹ dry matter that was near the normal range of this element in plants. Therefore, high concentrations of Cu and Co in these plants were caused by human activities and arise from soil and atmospheric pollution.