Accumulation of Cr in different vegetables and derivation of soil Cr threshold using the species sensitivity distribution method

Due to its high mobility and bioavailability, hexavalent chromium [Cr(VI)] in agricultural soil can be taken up by crops and pose threat to human being. In this study, two soils (Jiangxi red soil and Shandong fluvo-aquic soil) spiked with Cr(VI) and 8 common vegetable varieties were used to conduct the pot experiment. The bioconcentration factor (BCF) values based on the tetraacetic acid extractable Cr (EDTA-Cr) in soils were used to construct the species sensitivity distribution (SSD) curve. Afterwards, the soil Cr threshold was derived based on the critical BCF value and the permissible limit of Cr for vegetables. The results showed that when spiked with 5.6 mg kg−1 of Cr(Ⅵ), the soil EDTA-Cr concentrations were significantly increased compared with the control except Jiangxi red soil planted with carrot and radish, while the Cr concentrations in the edible parts of vegetables in both soils were below the permissible limit (0.5 mg kg−1 FW). However, there are dramatic differences in the accumulation of Cr by different varieties of vegetables. Apparent discrepancy was observed between the two soils for the bioconcentration of Cr by carrot. Among the leafy vegetables, lettuce and oilseed rape are the most and the least sensitive to Cr pollution, respectively. The safety threshold values of EDTA-Cr were 0.70 mg kg−1 for Shandong fluvo-aquic soil and 0.85 mg kg−1 for Jiangxi red soil, respectively. This study provides information on the safety production of vegetable products in Cr(Ⅵ) polluted soils and is helpful to the revision of soil quality standards of Cr.