The calculation of trace metal flux balances is used to predict long-term changes in soil levels of these pollutants, according to different scenarios of future cultivation practices. The aim is to determine the resultant flows of metals into the soil through atmospheric deposition and agricultural inputs, and output flow through harvesting and leaching, the latter of which may change with soil properties. This type of modelling had never been validated, due to the difficulty of setting up long-term experimental measurements. The model was therefore evaluated by reconstructing past flows of Cd, Cu, Pb and Zn and comparing their balances with current levels in the soil of the Grand Carré du Potager du Roi in Versailles, which has been used for market gardening for almost three and a half centuries.
The crop successions and fertiliser inputs applied to the Potager du Roi since its creation have been reconstructed on the basis of historical documents. Atmospheric deposition was estimated on the basis of published reconstructions. Export by crops was calculated using transfer factors from the BAPPET database. Metal leaching with water percolating through the soil was modelled by taking into account changes in metal solubility with soil organic matter content. This was modelled according to four scenarios involving the addition of ‘compost’, the main fertiliser used by the King's gardeners. This is a type of compost produced by the decomposition of straw used for the warm layers used to grow early vegetables and fruit. The topsoil in the Grand Carré is contaminated with trace metals to a level comparable to that found in French kitchen gardens.
The work carried out shows that if the input data are chosen on the basis of realistic scenarios, the modelling of trace metal fluxes can be used to predict the long-term trend in levels of these elements in cultivated soils (excluding exceptional contaminant events), and possibly adjust cultivation practices and the composition of inputs to limit soil contamination.
Référence : DOI 10.1016/j.jhazmat.2023.133259
Contact : thibault.sterckeman@inrae.fr
