Abstract
The risk assessment of mixtures of rare earth elements (REEs) is hampered by a lack of fundamental understanding of their interactions in different soil types. Here, we assessed mixture interactions and toxicity to Triticum aestivum of Y and Ce in four different soils in relation to their bioavailability. Mixture toxicity was modelled by concentration addition (CA) and independent action (IA), in combination with different expressions of exposure: three equilibrium-based doses (total soil concentrations [M]tot, free ion activity in soil solution {M3+}, and the fraction (f) of metal ions bound to the biotic ligands (BLs)) and one kinetically controlled dose ([M]flux) metrics. Upon single exposure, REE toxicity was increasingly better described when using exposure expressions based on deepened understanding of their bioavailability: [M]flux > f > {M3+} > [M]tot. The mixture analyses based on [M]tot and {M3+} displayed deviations from additivity depending on the soil type. With the parameters derived from single exposures, the BLM approach gave better predictions of mixture toxicity (R2 ~ 0.70) than when using CA and IA based on either [M]tot or {M3+} (R2 < 0.64). About 30% of the variance in toxicity remained unexplained, challenging the view that the free metal ion is the main bioavailable form under the BLM framework based on thermodynamic equilibrium. Toxicity was best described when accounting for changes in the size of the labile metal pool by using a kinetically controlled dose metric (R2 ~ 0.80). This suggests that dynamic bioavailability analysis could provide a robust basis for modeling and reconciling the interplays and toxicity of metal mixtures in different soils.
Original language | English |
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Article number | 109736 |
Pages (from-to) | 1-9 |
Number of pages | 9 |
Journal | Environmental Research |
Volume | 188 |
Early online date | 2 Jun 2020 |
DOIs | |
Publication status | Published - Sept 2020 |
Funding
This study was supported by the National Natural Science Foundation of China (No. 41701573, No. 41701571, No. 41877500, and No. 41977115), the National Key R&D Program of China (No. 2018YFC1800600, No. 2018YFD0800700), the Research Fund Program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (No. 2018K01), Science and Technology Program of Guangzhou, China (No. 201904010116), and Fundamental Research Funds for the Central Universities (No. 19lgpyl50).
Funders | Funder number |
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National Key R&D Program of China | |
National Natural Science Foundation of China | 41701571, 41701573, 41877500, 41977115 |
Guangzhou Science and Technology Program key projects | 201904010116 |
Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | 2018K01 |
National Key Research and Development Program of China | 2018YFD0800700, 2018YFC1800600 |
Fundamental Research Funds for the Central Universities | 19lgpyl50 |
Keywords
- Bioavailability
- Mixture
- Rare earth
- Toxicity
- Triticum aestivum