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The potential ecological risk of soil trace metals following over five decades of agronomical practices in a semi-arid environment

Rezapour, Salar, Kouhinezhad, P., Samadi, A.
Chemistry in ecology 2018 v.34 no.1 pp. 70-85
Calcisols, Cambisols, Chernozems, Vertisols, cadmium, copper, manganese, pesticides, phosphorus fertilizers, risk, semiarid zones, soil profiles, zinc
The concentration and potential ecological risk of Mn, Zn, Cu, and Cd in the surface soils (0–30 cm) belonging to 12 soil profiles and 4 soil types (Vertisols, Chernozems, Calcisols, and Cambisols) from the cultivated soils and the corresponding uncultivated soils were investigated. Long-term cultivation caused a considerable build-up diethylene-triamine pentaacetic acid (DTPA)-extractable Mn (7–55%), and Cd (12–31%) as well as the total form of Zn (3–14%), Cu (8–25%), and Cd (33–78%) in all soil types. Following long-time cropping, total Zn (mean = 73 mg kg⁻¹), Cu (mean = 33 mg kg⁻¹), and Cd (mean = 3.14 mg kg⁻¹) and DTPA Zn (mean = 1.2 mg kg⁻¹) and Cu (mean = 2.44 mg kg⁻¹) were below their maximum allowable limits. However, the average amount of DTPA Cd in the tilled soils (min = 0.4, max = 0.75, mean = 0.55 mg kg⁻¹) was above its maximum permissible limit mainly due to the over application of phosphate fertilisers and the pesticides. Considering the potential ecological risk (RI) assessment of the cultivated soils (min = 44, max = 70, mean = 54), the soil types were categorised as low (RI ≤ 50) to moderate (50 < RI ≤ 100) potential ecological risk.