Phytomanagement solutions for Cd-Pb contaminated garden soils: results of field and pot experiments

Central Belgium has a rich industrial history that has left a heavy heritage of contaminated sites. Food safety has become a prominent public concern when transfers of metals from soil to vegetables were measured in private and market gardens, even in areas with slight to moderate contaminations. Associating high biomass crops to target vegetables may be a promising approach since it allows food production to continue while remediating soil.
Field and pots trials were conducted to investigate the combination of Swiss chard with accumulator crop species, Helianthus annuus or Brassica juncea, and the effects of intercropping on growth performance and metal uptake by the involved plants. The experiments were performed on Cd-Pb contaminated soil. The impacts of organic amendments, biochar and green waste compost, on the phytoremediation efficiency and soil properties were also assessed.
Compared with Swiss chard monoculture, intercropping with high biomass crops significantly reduced chard biomass production and did not significantly decrease chard shoot concentration. The labile metal fraction and soil pH were not significantly different between amended and unamended treatments. However, the application of green waste compost has limited the Zn and Cd uptake by chard.
Our results do not show evidence of benefit in terms of metal uptake by chards from intercropping and that a longer time period may be needed to determine/highlight the effects of organic amendments addition on soil properties. Further studies are still needed to identify remediation strategies allowing a safe production of vegetables in areas impacted by small atmospheric contaminations.