Phytoextraction of soil trace elements by willow during a phytoremediation trial in Southern Québec, Canada

Abstract

The phytoextraction of the trace elements (TEs) As, Cd, Cu, Ni, Pb, and Zn by willow cultivars (Fish Creek, SV1 and SX67) was measured during a 3-year field trial in a mildly contaminated soil. Biomass ranged from 2.8 to 4.4 Mg/ha/year at 30,000 plants/ha. Shoots (62%) were the main component followed by leaves (23%) and roots (15%). Biomass was positively linked to soluble soil dissolved organic carbon, K, and Mg, while TEs, not Cd and Zn, had a negative effect. The TE concentration ranking was: Zn > Cu > Cd > Ni, Pb > As, and distribution patterns were: (i) minima in shoots (As, Ni), (ii) maxima in leaves (Cd, Zn), or (iii) maxima in roots (Cu, Pb). Correlations between soil and plant TE were significant for the six TEs in roots. The amounts extracted were at a maximum for Zn, whereas Fish Creek and SV1 extracted more TE than SX67. More than 60% (91-94% for Cd and Zn) of the total TE was in the aboveground parts. Uptake increased with time because of higher biomass. Fertilization, the selection of cultivars, and the use of complementary plants are required to improve productivity and Cd and Zn uptake.

The Suitability of Short Rotation Coppice Crops for Phytoremediation of Urban Soils

“…Poplar and Salix gave yields not statistically different from each other (at p = 0.05), probably due to water scarcity in the field, as from previous studies in northern Italy with fertilized and irrigated soil, poplars are usually more productive [29,37]. The results were, however, in line with productions made on marginal areas and on contaminated soils [13,17]. In this case, to maximally limit the management of the parcels it was chosen not to irrigate the field unless in the case of extreme drought.…”

“…Generally, productivity was not higher as in the literature [13,29], probably due to low soil fertility or the limited quantity of water. However, as the plant did not present symptoms of suffering, to increase biomass production a higher planting density is attainable, in order to store higher amounts of PTE in plant tissues.…”

“…Within an urban framework, phytostabilization techniques could be used as an initial step towards remediation because, although PTEs could be stabilized, the concentrations do not decrease and, if soil particles are moved (e.g., after wind or water erosion) or change oxidation state (e.g., due to flooding episodes), contaminated particles could exert their toxicity in their new environment. Phytoextraction has, conversely, the aim to remove the contaminants from the soil by either using hyper-accumulator plants [12] or plants with a lower specific uptake of pollutants but high growth rate and biomass production [9,13].…”

Cadmium Effects on Mineral Accumulation and Selected Physiological and Biochemical Characters of Salix babylonica L.

“…There have been many reports since then on the use of some crop plants and forest species (including poplar and willows) to remove Cd from contaminated soils [4,10,25,[37][38][39][40]. It has been reported that a few clones of willows have high heavy metal tolerance [13][14]41].…”

Preliminary results of the tolerance to inorganic contaminants and phytoextraction potential of twelve ornamental shrub species tested on an experimental contaminated site

“…The efficiency of phytoextraction depends on the capacity of the plants to concentrate and accumulate contaminants in their aerial parts. While highly productive species will be more effective for phytoextraction (Kacál-ková et al 2014, Courchesne et al 2017) the actual efficiency of phytoextraction depends primarily on the capacity of plants to establish and survive on contaminated sites (Walter et al 2003). Consequently, it is important to identify plants well adapted to the urban context and capable of supporting abiotic stresses related to these conditions, specifically water and heat stresses, air pollution, etc.…”