Experiment 3: Effects of Rare Earth Element mixtures (lanthanum, neodymium, cerium) on terrestrial crops and native plants: uptake, accumulation, soil pH and calcium
The objective of this experiment was to expose plants to a mixture of the three most common and widely used Rare Earth Elements (REEs) in soils: lanthanum (La), neodymium (Nd) and cerium (Ce). It was hypothesized that plant sensitivity to La, Nd and Ce would be additive, and would increase with overall soil REE concentration. In addition, it was hypothesized that REE uptake would be similar for all three REEs (measured concentrations in plants would be equal) if REE soil concentrations were equal (La = Nd = Ce). Deviations in uptake would indicate potential higher risks of one REE over the others. Ny, Ce, and La were tested in soil mixture with doses based on the previously identified IC25 and IC50 values for native plant species (see Experiments 1 and 2). Doses were equal for all REEs in a given dose (i.e. 100 mg/kg Nd, Ce, and La), and followed a geometric progression. Due to the presumed influence of pH and calcium (Ca) on bioavailability and uptake, two soil pH levels (one acidic, one closer to neutral) and two Ca levels were also be tested. Two species were tested: the native common milkweed, Asclepias syriaca as well as the crop tomato, Solanum lycopersicum var. Beefsteak. The full experimental set-up was: 2 soil pH levels x 2 Ca concentrations x 4 REE doses (including controls) x 2 plant species x 6 replicates = 192 pots. The experiment was conducted in NWRC greenhouses of Environment and Climate Canada with plants tested individually in pots. Measured endpoints included germination percent and rates, aboveground and below ground biomass. In addition, to address plant accumulation rates, tissue concentrations (roots and shoots) of the REEs, as well as calcium, were measured. There was no obvious effect of treatment on the overall number of germinating seeds of A. syriaca or S. lycopersicum. Speed of germination of both species was found to be significantly affected by the soil treatments. For A. syriaca, a marginally significant main effect of soil REE dose was found but no main effects for soil pH or soil Ca; however, there was a significant soil pH x soil Ca interaction. Speed of germination of S. lycopersicum was found to be significantly affected by both soil pH and soil total REE concentration but there was no main effect of soil Ca levels, and no significant interactions were identified. Effects of soil parameters (pH, Ca, and REE) on A. syriaca and S. lycopersicum root and shoot biomass were complex. In general, a reduction in biomass was observed at high REE doses but there were multiple interactions with soil pH and Ca. The measured concentrations of each individual REE in plant tissues (both roots and shoots) were found to consistently increase with increasing soil REE dose within a given soil pH, soil Ca treatment. For all treatments, the measured concentration of a given REE was always greater in the roots than in the corresponding shoots. Measured REE soil concentrations tended to follow a consistent pattern of [Ce] > [Nd] > [La] for all soil treatment levels (soil pH, soil Ca, soil REE). However, results for the REE-dosed soils across all soil pH x soil Ca treatments consistently followed a pattern of [La] > [Ce] > [Nd] for both tissues in both species with the only exceptions found for the roots of both A. syriaca and S. lycopersicum in the high soil pH, low Ca, 150 mg REE kg-1 treatment ([Ce] > [La] > [Nd]). The overall result for REE-dosed soils appears to indicate that La may be more readily taken up by plants, followed by Ce and then Nd. All REE control soils were found to contain background levels of the three tested REEs: La (3.16 ± 0.01 mg kg-1 dry soil), Ce 6.94 ± 0.21 mg kg-1 dry soil), and Nd (3.91 ± 0.10 mg kg-1 dry soil). REE recovery rates, calculated as: (measured REE soil concentration – background level concentration)/nominal REE soil concentration, spanned from 93-117%, 98-124%, and 96-127% for La, Ce, and Nd respectively.
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- File Identifier
- 60f7aa51-5d3f-48ee-9f8a-cfcb3af77a85 XML
- Date Stamp
- 2021-05-12T06:01:50
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eng; CAN
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- UTF8
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- Dataset
http://ec.gc.ca
Data identification
- Title
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Experiment 3: Effects of Rare Earth Element mixtures (lanthanum, neodymium, cerium) on terrestrial crops and native plants: uptake, accumulation, soil pH and calcium
- Date (Creation)
- 2018-06-14
- Date (Publication)
- 2018-06-14
- Status
- Completed
- Metadata language
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eng; CAN
- Character set
- UTF8
- Topic category
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- Environment
- Maintenance and Update Frequency
- As needed
- Spatial representation type
- Vector
613-998-0458
Keywords
- Theme
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Rare earth elements, lanthanum, neodymium, cerium, metals, phytotoxicity
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Government of Canada Core Subject Thesaurus
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Toxicology
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ECCC Information Category EN
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Nature and Biodiversity - Contaminants
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Business Functions
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Assess Toxicity, Manage and Monitor for Environmental Presence of Hazardous Substances and Waste
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Assess Toxicity of Substance
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Geography
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National (CA)
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National (CA)
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external.theme.EC_Branch
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Science and Technology Branch
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external.theme.EC_Directorate
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Wildlife and Landscape Science
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external.theme.GC_Security_Level
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Confidential
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Open Government Licence - Canada ( http://open.canada.ca/en/open-government-licence-canada)
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- License
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- License
- Begin Date
- 2018-06-14
- End Date
- 2018-12-18
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))
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- http://www.epsg-registry.org / EPSG:4326 / Inconnue
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- CSV ( CSV)
http://ec.gc.ca
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