Salix caprea · Atlas of Contaminated Sites

How it works

Mechanisms: phytoextraction

Contaminants

Contaminant	Evidence	What was shown
Cadmium	field	Survey of adult trees growing on contaminated sites in Central Europe: up to 116 mg/kg Cd in leaves of S. caprea; small year-to-year variation; lowest concentration in wood, rising towards leaves and fine roots (Unterbrunner et al. 2007). Unterbrunner et al., Heavy metal accumulation in trees growing on contaminated sites in Central Europe, Environ. Pollut. 148:107, 2007
Zinc	field	In the same survey up to 4,680 mg/kg Zn in leaves. Leaf concentrations are unrelated to total or labile soil content: the accumulation factor falls as soil concentration rises (Unterbrunner et al. 2007). Unterbrunner et al., Environ. Pollut. 148:107, 2007

Contaminant

Evidence

What was shown

field

Survey of adult trees growing on contaminated sites in Central Europe: up to 116 mg/kg Cd in leaves of S. caprea; small year-to-year variation; lowest concentration in wood, rising towards leaves and fine roots (Unterbrunner et al. 2007).

Unterbrunner et al., Heavy metal accumulation in trees growing on contaminated sites in Central Europe, Environ. Pollut. 148:107, 2007

Zinc

field

In the same survey up to 4,680 mg/kg Zn in leaves. Leaf concentrations are unrelated to total or labile soil content: the accumulation factor falls as soil concentration rises (Unterbrunner et al. 2007).

Unterbrunner et al., Environ. Pollut. 148:107, 2007

Limits

The data are a survey of wild plants, not a clean-up trial with a mass balance of metal removed. Metal concentrates in the leaves, which on falling return it to the soil and expose herbivores. It roots from cuttings less readily than other willows.

Where it has been tried

Brescia-Caffaro

PhytoremediationGreenhouse, with soil from the site, 2015–2016

Festuca arundinacea, Phalaris arundinacea, Cucurbita pepo subsp. pepo, Medicago sativa, Brassica juncea, Salix caprea, Athyrium filix-femina

The University of Insubria, the University of Milan and ERSAF took about 2,500 kg of soil from the site and grew plants on it in a greenhouse for 18 months (May 2015 – November 2016) in 6 kg pots: ten treatments in triplicate with seven species, intercropping, compost, redox cycles and ammonium thiosulphate, with unplanted controls. It is a semi-field trial, not an open-field one.

Outcome After 18 months total PCBs had fallen by 14–20%. The best treatments (Festuca arundinacea with compost or intercropped with pumpkin; alfalfa with Rhizobium and mycorrhizal fungi) reached about 20%. For dioxins and furans tall fescue alone gave reductions of 11–24% depending on the congener, with half-lives of 2.5–5.8 years. The authors name the short duration, against the persistence of these compounds, as a limit.