Integrating bioavailability and soil aging in the derivation of cadmium thresholds for agricultural soil using crop species sensitivity distributions

Lijun Li a and Y. Ma a*

Institute of Agricultural Resources and Regional Planning,

Chinese Academy of Agricultural Sciences, China

lilijun@caas.cn

It is imperative to derive an appropriate cadmium (Cd) threshold for rice to ensure the Cd concentration of rice grains meet the food safety standard. In this paper, a robust methodology is presented, taking the variations of aging time and cultivars and soil properties into account to derive soil thresholds for cadmium (Cd) applying species sensitivity distribution (SSD). 39 cultivars of rice were selected to investigate their sensitivity differences for accumulating Cd. Empirical soil–plant transfer model was used to normalize the bioaccumulation data of non-model cultivars. The added hazardous concentration for protecting 95% of the cultivars not exceeding the food quality standard (HC5add) were then calculated from the Burr Type III function fitted SSD curves. The derived soil Cd thresholds based on the added risk approach were presented as continuous or scenario criteria depending on the combination of soil pH and OC. The prediction model for HC5add was applied to the data from the field experimental sites to check its validity and applicability. Most of the soil Cd safety threshold in the 8 field experimental sites lay below the 1:1 line and all of them were within the 2-fold prediction interval. This work provides information for the establishment of soil environmental quality standards regarding Cd contamination.

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