Plant, tree

Paulownia tomentosa (Thunb.) Steud.

Princess tree, empress tree

A very fast-growing tree with large leaves and high transpiration. In Tuscany it was used in a full-scale phytoremediation together with poplar and broom; metals stay mainly in the roots.

Jean-Pol GRANDMONT, CC BY 2.5

How it works

Mechanisms: phytostabilisationphytoextraction

Contaminants

Contaminant	Evidence	What was shown
Petroleum hydrocarbons	field	Full-scale intervention on 10,000 m² of soil historically contaminated by metals and hydrocarbons, with Populus nigra var. italica, Paulownia tomentosa, Cytisus scoparius and natural vegetation: in three years total hydrocarbons −40% and metals −20–40%, down to values below legal limits, with soil enzyme activities rising (Macci et al. 2013). Macci et al., A real-scale soil phytoremediation, Biodegradation 24:521, 2013
Lead	greenhouse	Pilot-scale study with EDTA, tartrate and glutamate: root/shoot concentration ratios of 11–39 for Pb, 9–18 for Cd, 7–17 for Cu and 3–5 for Zn; with 10 mM EDTA root Pb rose to 359 mg/kg against 128 in the control, and EDTA gave no greater accumulation than tartrate or glutamate (Doumett et al. 2008). Doumett et al., Heavy metal distribution between contaminated soil and Paulownia tomentosa, in a pilot-scale assisted phytoremediation study: influence of different complexing agents, Chemosphere 72:1481, 2008

Contaminant

Evidence

What was shown

Petroleum hydrocarbons

field

Full-scale intervention on 10,000 m² of soil historically contaminated by metals and hydrocarbons, with Populus nigra var. italica, Paulownia tomentosa, Cytisus scoparius and natural vegetation: in three years total hydrocarbons −40% and metals −20–40%, down to values below legal limits, with soil enzyme activities rising (Macci et al. 2013).

Macci et al., A real-scale soil phytoremediation, Biodegradation 24:521, 2013

Lead

greenhouse

Pilot-scale study with EDTA, tartrate and glutamate: root/shoot concentration ratios of 11–39 for Pb, 9–18 for Cd, 7–17 for Cu and 3–5 for Zn; with 10 mM EDTA root Pb rose to 359 mg/kg against 128 in the control, and EDTA gave no greater accumulation than tartrate or glutamate (Doumett et al. 2008).

Doumett et al., Heavy metal distribution between contaminated soil and Paulownia tomentosa, in a pilot-scale assisted phytoremediation study: influence of different complexing agents, Chemosphere 72:1481, 2008

Limits

In the full-scale trial three species and natural vegetation grew together: the contribution of paulownia alone cannot be told apart, and there is no comparison with unplanted soil. Metals stop in the roots, so this is stabilisation more than extraction. An alien species in Europe that seeds freely: to be assessed before planting.