Predictive Modelling of Lead and Cadmium Uptake by Lactuca Sativa : Potential Uncertainties Introduced by Presence/Absence of Aerial Deposition and Implications for Selection of Parameterisation Data

We developed regression models to predict uptake of cadmium and lead in lettuce from data on soil metal concentration, pH and organic carbon. To assess the impact of physical contamination (i.e., aerial deposition and soil-splash) on uptake, separate models were parameterised for indoor- and outdoor-grown lettuce, assuming the physical contamination to be negligible for indoor conditions. Both cadmium models showed high model fit and strong predictive performance, when tested on an independent dataset, suggesting uptake via roots to be dominant. For Pb, the indoor model performed better than the outdoor model, indicating that physical contamination contributes significantly to uptake. Our results highlight the importance of the parameterisation data when developing uptake models for risk assessment. Regression models for predicting Pb concentration in lettuce based on indoor data should not be used for predicting lettuce concentrations cultivated in outdoor conditions unless the contribution of physical contamination is explicitly accounted for