Phytotoxicity of soil trivalent chromium to wheat seedlings evaluated by chelating resin extraction method

A pot experiment of wheat seedlings with the chelating exchange resin Chelex 100, which is used to extract trivalent chromium (Cr[III]) from the soils, was conducted to examine the phytotoxicity of Cr(III)-spiked soils. Plant height and dry weight of the wheat seedlings were adversely affected by the Cr(III)-spiked acidic soils, whereas growth inhibition of wheat seedlings was not found in alkaline soils with the same quantities of added Cr(III). The concentrations of Cr in plant tissues corresponding to 50% reduction (PT50) of plant height and dry weight were 97.6 and 126.0 mg kg(-1), respectively. The amount of soil resin-extractable Cr(III) increased with the increase of Cr(III) in the Cr(III)-spiked acidic soils. However, no detectable Cr(III) (<= 0.05 mg kg(-1)) was extractable from the alkaline soils. In addition, the reduction of plant height and dry weight of wheat seedlings and the increase of plant Cr concentration and Cr uptake had a pronounced correlation to the quantity of soil resin-extractable Cr(III) retained by Chelex 100 resin. The correlation between the relative plant height of the wheat seedlings and the amount of soil resin-extractable soil in a logarithmic scale was well fitted to an exponential type of dose-response relation model (r(2) = 0.97). Therefore, the resin extraction method using Chelex 100 could be a reliable method for assessing the phytotoxicity of Cr(III) in Cr-contaminated soils. Based on the dose-response relationship model, the effective concentrations calculated for resin-extractable Cr(III), resulting in 10% and 50% growth inhibition (EC10 and EC50), were 11.4 and 57.8 mg kg(-1) respectively.