Assessment of trace element concentrations in soil and plants from cropland irrigated with wastewater

Samples of soil and food plants were collected from wastewater-irrigated fields in the vicinity of Gaziantep, in southeast Turkey, and analyzed for several trace elements (TEs). The concentrations of Co, Mo and Zn in edible portions of corn, mint and vegetables (eggplant, pepper and tomato) were 0.03-0.66, 0.1-3.2 and 8-148 mg kg⁻¹, respectively. In the edible portions of corn and mint, Cd, Cr, Cu, Ni and Pb concentrations in all samples were <0.01-0.05, 2.0-5.5, 6-47, 0.6-6.7 and 0.2-3.5 mg kg⁻¹, respectively. No single plant species had consistently high concentrations of all metals. For example, corn had the highest concentration of Zn (89 mg kg⁻¹), but the lowest concentration of Cd (<0.01 mg kg⁻¹). The maximum concentrations of some TEs in some crop samples, as well as soil samples, exceeded certain threshold values set in Turkey and other countries. For some TEs there was little difference between wastewater-irrigated and control soil concentrations. Transfer factors (TFs; plant concentration/soil concentration) were high for Cu, Zn and Mo, in comparison with the other TEs (Cd, Co, Cr, Ni and Pb). Higher uptake of certain metals may be associated with the dominant form of the element in the soil matrix. The uptake of chemicals to plant tissues is influenced by the chemical and physical characteristics of the soil and species-specific factors. Although the geochemistry of the region plays a significant role in the levels of TEs in soil and plants, bioaccumulation of metals and subsequent toxicity to plants and animals can be exacerbated by higher environmental concentrations caused by wastewater irrigation and other anthropogenic factors.