Assessing phytotoxicity of trace element-contaminated soils phytomanaged with gentle remediation options at ten European field trials

Gentle remediation options (GRO), i.e. in situ stabilization, (aided) phytoextraction and (aided) phytostabilisation, were implemented at ten European sites contaminated with trace elements (TE) from various anthropogenic sources: mining, atmospheric fallout, landfill leachates, wood preservatives, dredged-sediments, and dumped wastes. To assess GRO performance, topsoils were collected in field trials, potted, and cultivated with lettuce (Lactuca sativa L.) for 48 days. Shoot dry weight (DW) yield, photosynthesis efficiency and major element and TE concentrations in the soil pore water and lettuce shoots were measured. GRO implementation had a limited effect on TE concentrations in the soil pore water, although use of multivariate Co-inertia Analysis revealed a clear amelioration effect in phytomanaged soils. Phytomanagement increased shoot DW yield at all industrial and mine sites, whereas in agricultural soils improvements were produced in one out of five sites. Photosynthesis efficiency was less sensitive than changes in shoot biomass and did not discriminate changes in soil conditions. Based on shoot biomass data, compost amendment followed by phytoextraction yielded better results than phytostabilisation, although shoot ionome data prove that care is needed to avoid soil nutrient depletion by repeated harvesting