Abstract: A pot experiment was conducted to investigate Cd accumulation in two genotypes of rice cultivars, different in Cd enriching capacity and to derive total and available Cd fraction based soil Cd threshold value in rice producing area. Results show that Cd, at 0- 15 mg•kg^-1 had no significant inhibitive effect on growth or yield of rice. Cd accumulation in rice, in general, increased with increasing soil Cd concentration, and Cd concentration in different rice organs varied, showing an order of stalk, leaf,brown rice,and husk. However, no significant difference was found between the two rice genotypes in plant growth and Cd accumulation capacity in the experiment. Cd in brown rice was significantly related to soil total Cd and CaCl₂ extractable Cd. Based on the national food hygienic standards (GB 2762-2005) and Cd accumulation characteristics of the two rice genotypes, Cd threshold value of the Fluvo-aquic soils (pH 7.71) in Tianjin was derived to be 2.1 mg•kg^-1 and CaCl₂ extractable Cd threshold value of the soil 5.7 μg•kg^-1. The findings of this study can be used as scientific reference for  revision of the national standards for soil environment quality and for suitability assessment of soils for rice production.

Key words: rice, cadmium, brown rice, total Cd concentration, available Cd concentration, threshold value