Cr(III) accumulation and phytoavailability in alkaline soils contaminated by tannery sludge
2003
Ma, Hongrui | Wang, Xiaorong | Zhang, Chuanbo
An investigation was carried out into the crop uptake of Cr(III) and its accumulation in two alkaline soils that have received tannery sludge as organic fertilizer for many years. The Cr(III) concentrations in the soils did not exceed the safe levels. However, Cr content in wheat and rice straw was up to 17 mg kg⁻¹ in recently sludge-applied soils, and Cr content in wheat grain exceeded the hygienic standard of China for food. After the sludge application, Cr(III) remained in top soil in the first few years and its transfer to a depth of 60cm was discovered in the soils with application of the sludge for over 15 years. Asequential extraction procedure and seedling culture experiment were used to assess the Cr(III) chemical forms and their phytoavailability. The results showed that Cr in straw and wheat grain was significantly correlated with total Cr(III), H₂O-NH₄OAc and DPTA extractable Cr(III). 2 mol L⁻¹ HCl extractable Cr(III) was an important source of soil Cr available to the crops. In the seedling culture experiment, it was discovered that 1 mol L⁻¹NH₄OAc and 0.05 mol L⁻¹ DPTA exhibited higher extraction capacities for Cr(III) than plant uptake at lower soil Cr(III) concentration, while they were coincident at higher Cr(III) concentration. Cr content in wheat seedlings reached a maximum of 23.5 mg kg⁻¹, which was hardly attainable under field conditions.
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