Modelling of long term Zn, Cu, Cd, Pb dynamics from soils fertilized with organic amendments

Abstract

<jats:p>Abstract. Soil contamination by trace elements (TEs) is a major concern for sustainable land management. One potential source of excessive inputs of TEs into agricultural soils are organic amendments. Here, we use dynamic simulations carried out with the IDMM-ag model to describe observed trends of topsoil Zn, Cu, Pb and Cd concentrations in a long-term crop trial in Switzerland, where soils plots have been treated with differing organic amendments, particularly farmyard manure, sewage sludge and compost. IDMM-ag requires the definition of a parsimonious set of boundary conditions. The model adequately reproduced the metal EDTA-extractable concentrations in ZOFE when site-specific soil lateral mixing, due to mechanically ploughing of small plots, was introduced. Calibration of an additional metal input flux was necessary to fit the measured data, indicating that knowledge gaps in quantifying historical metal inputs can affect field-scale simulations even in a well-characterized field. Projections of soil metal content in the long-term showed that, under stable organic amendment application rates, Zn and Cu labile concentrations might pose toxicological hazard for the soil ecosystem, particularly in the sewage sludge-amended plots. The sewage sludge topsoil was characterized by some variability in the organic matter composition, potentially due to the applied sewage sludge quality, which might affect the metal lability: this effect should be accounted for in models. This study takes a step forward in assessing potential and limitations of the IDMM-ag model to predict TEs long-term dynamics in agricultural fields, paving the way to quantitative applications of TEs modelling at field and larger scales. </jats:p>