Populus × canadensis · Atlas of Contaminated Sites

How it works

Mechanisms: phytodegradationphytovolatilisationhydraulic controlphytoextraction
Native range: Cultivated hybrid

Contaminants

Contaminant	Evidence	What was shown
Zinc	field	Two-year field trial under hot-arid Mediterranean climate, on moderately contaminated soil: poplar accumulated 3,200 g Zn/ha/year and 182 g Cu/ha/year and lowered the extractable fraction of Cd (37%), Ni (49%), Pb (46%) and Zn (63%); total soil content did not change (Guidi Nissim et al. 2018; the abstract does not name the clone). In a coppice of 17 clones on a former waste site in Belgium, the best clones removed 2.0–2.4 kg Zn/ha and 47–57 g Cd/ha over two years (Laureysens et al. 2005). Guidi Nissim et al., Trace element phytoextraction from contaminated soil: a case study under Mediterranean climate, Environ. Sci. Pollut. Res. 25:9114, 2018 Laureysens et al., Clonal variation in heavy metal accumulation and biomass production in a poplar coppice culture. II. Vertical distribution and phytoextraction potential, Environ. Pollut. 133:541, 2005
Chlorinated solvents (TCE, PCE, chloroform)	laboratory	Twelve organic compounds common at hazardous waste sites, labelled with carbon-14 and supplied hydroponically to hybrid poplars: uptake and partitioning to tissues depend mainly on the octanol-water coefficient (log Kow); for volatile organic compounds, translocation followed by transpiration from leaves to the air is a significant pathway (Burken and Schnoor 1998). Burken and Schnoor, Predictive relationships for uptake of organic contaminants by hybrid poplar trees, Environ. Sci. Technol. 32:3379, 1998

Contaminant

Evidence

What was shown

field

Two-year field trial under hot-arid Mediterranean climate, on moderately contaminated soil: poplar accumulated 3,200 g Zn/ha/year and 182 g Cu/ha/year and lowered the extractable fraction of Cd (37%), Ni (49%), Pb (46%) and Zn (63%); total soil content did not change (Guidi Nissim et al. 2018; the abstract does not name the clone). In a coppice of 17 clones on a former waste site in Belgium, the best clones removed 2.0–2.4 kg Zn/ha and 47–57 g Cd/ha over two years (Laureysens et al. 2005).

Chlorinated solvents (TCE, PCE, chloroform)

laboratory

Twelve organic compounds common at hazardous waste sites, labelled with carbon-14 and supplied hydroponically to hybrid poplars: uptake and partitioning to tissues depend mainly on the octanol-water coefficient (log Kow); for volatile organic compounds, translocation followed by transpiration from leaves to the air is a significant pathway (Burken and Schnoor 1998).

Burken and Schnoor, Predictive relationships for uptake of organic contaminants by hybrid poplar trees, Environ. Sci. Technol. 32:3379, 1998

Limits

For metals, removal is a few kilograms of zinc and tens of grams of cadmium per hectare: soil is not cleaned quickly. Clones I-214 and Eridano, grown on soil amended with tannery sludge, accumulated only small amounts of metals (Tognetti et al. 2004). Burken and Schnoor's data on organics are hydroponic. The field trials cited involve different clones and hybrids: the result depends on the clone.

Where it has been tried

Scarlino, ceneri di arsenopirite (ex Nuova Solmine)

PhytoremediationField scale

Pteris vittata, Populus deltoides 'Dvina', Populus × canadensis 'Orion'

Ciurli, Lenzi, Alpi and Pardossi (University of Pisa) planted the fern Pteris vittata and two poplar clones on the cinders, in pots and on site, following survival, tissue arsenic and stress markers for 24 months. The abstract of that paper does not name the site; Scarlino is given in the same group's later study on the same material. In a greenhouse, Lampis and colleagues then grew the fern for four months on cinders and compost, with and without arsenic-resistant bacteria isolated from the site.

Outcome In the field the authors judge the fern-poplar co-planting suitable, but the abstract gives no amount of arsenic removed and notes that irrigation, tillage and amendments are needed for the plants to establish. In the greenhouse the bacteria raised fern biomass by up to 45% and arsenic removal efficiency from 13% to 35% in four months.