Suitability of marginal sites contaminated by trace elements for the production of non-food biomass: lessons from lysimeter experiments

Abstract

In the context of the post-industrial revolution, phytomanagement techniques for the rehabilitation of polluted sites are considered promising new techniques but still present some difficulties in their application. The risk of pollutant transfer must therefore be limited. The general aim of this work was to assess the suitability of brownfield sites for biomass production by setting up two groups of experiments using lysimeters. The first experiment aimed to assess the impact of three types of fertilisers applied at different doses on biomass production and on the leaching of trace elements and total nitrogen. The second experiment was part of the ECOSOL project and involved several varieties of rapeseed as well as herbaceous plants. The overall objective of this project was to assess the impact of plant growth on trace element solubility.

The first experience has shown that increasing nitrogen application to the soil increases biomass production, regardless of the fertilisation used. However, given the large amount of leached nitrogen and the possible increase in pH induced in the case of mineral nitrogen, organic fertilisation was considered for fertilisation advice, as organic amendments seemed to stand out positively. In particular, sludge sometimes reduced the bioavailability of certain trace elements while allowing a regular supply thanks to the mineralisation of organic nitrogen. The increase in biomass on unpolluted soil was extremely marked compared to polluted soil, and the quantities of phyto-extracted trace elements were higher in unpolluted soil for Cd and Zn and in polluted soil for Cu and Pb. As very small quantities of trace elements were detected in the leachate, no trend was identified regarding their evolution.

For the second experiment, no results were considered to be of good quality regarding the temporal evolution of the leachate. This lack of data did, however, make it possible to provide perspectives and to highlight the possibility of selecting varieties according to biodiversity criteria for future experiments.