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Abstract
The combination of food quality standard and soil-plant transfer models can be used
to derive critical limits of heavy metals for agricultural soils. In this paper, a
robust methodology is presented, taking the variations of plant species and cultivars
and soil properties into account to derive soil thresholds for lead (Pb) applying
species sensitivity distribution (SSD). Three species of root vegetables (four cultivars
each for radish, carrot, and potato) were selected to investigate their sensitivity
differences for accumulating Pb through greenhouse experiment. Empirical soil-plant
transfer model was developed from carrot New Kuroda grown in twenty-one soils covering
a wide variation in physicochemical properties and was used to normalize the bioaccumulation
data of non-model cultivars. The relationship was then validated to be reliable and
would not cause over-protection using data from field experimental sites and published
independent studies. 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 Pb thresholds based on the added
risk approach (total soil concentration subtracting the natural background part) were
presented as continuous or scenario criteria depending on the combination of soil
pH and CEC.