Characterizing the solid–solution partitioning coefficient and plant uptake factor of As, Cd, and Pb in California croplands

In risk assessment models, solid–solution partition coefficient, Kd, and plant uptake factor, PUF, are often employed to depict the fate and transport of trace elements in soils. The trustworthiness of risk assessments depends on the reliability of the parameters used. In this study, we examined Kd and PUF for As, Cd and Pb based on soils and plant tissues obtained from 70 crop production fields in California. We also examined the California portion of a nationwide survey of trace elements in cropland soils conducted by the Soil Survey, Natural Resources Conservation Service, USDA. Results showed that the Kd and PUF for cropland soils are probabilistic in nature and follow log-normal distributions. The trace element concentration of the soil solution did not appear to be a more appropriate estimator of PUF than the total soil element content. The Kd used in the CDFA (California Department of Food and Agriculture) study had a much wider range than that could occur in California croplands while the PUF used in the CDFA risk assessment was comparable to patterns observed in the field measurements.