Accumulation and bioavailability of copper and nickel in wheat plants grown in contaminated soils from the oasis, northwest China

This paper studied the accumulation and bioavailability of copper and nickel in wheat plants grown in contaminated soils from the oasis, northwest China. The concentrations of Cu and Ni in studied soils were all more than Cu and Ni limit of grade II soil environmental quality standards in China; furthermore the concentration of Cu in soil S5 and the concentrations of Ni in soil S1, S3, S5, and S6 exceeded grade III soil environmental quality standards in China. Among eight extractants, the extractable Cu concentrations in soils generally followed the descending order EDTA > Citric acid > NH4Ac > NH4NO3 > MgCl2 ≈ Tartaric acid > Acetic acid > Oxalic acid. The extraction capacity of Ni was as follow: Citric acid > EDTA > NH4Ac > tartaric acid > NH4NO3 ≈ Acetic acid ≈ Oxalic acid > MgCl2. The sequences of Ni average concentrations in different parts of the wheat plant were roots > leaves > shells > stocks > grains; the sequences of Cu average concentrations in different parts were also roots > leaves > shells > grains > stocks. Soil studied is not fit to plant the wheat crops for human consumption; soils studied posed high potential health risk for human health through food chains. Average Bio-concentration factor (BCF) and translocation factor (TF) of Cu in different parts of wheat plants were greater than those of Ni. The process of Cu and Ni uptake and accumulation by wheat plants were probably linked to the concentrations of available copper and nickel in the oasis soils, physical and chemical parameters of soils, and different parts of wheat plants. Citric acid and NH4Ac extraction procedures provided a good indication of Cu bioavailability among nine kinds of evaluation methods.