Coupling mixture reference models with DGT-perceived metal flux for deciphering the nonadditive effects of rare earth mixtures to wheat in soils

Bing Gong, Erkai He, Willie J.G.M. Peijnenburg, Yuichi Iwasaki, Cornelis A.M. Van Gestel, Xinde Cao, Ling Zhao, Xiaoyun Xu, Hao Qiu*

*Corresponding author for this work

    Research output: Contribution to JournalArticleAcademicpeer-review

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    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 languageEnglish
    Article number109736
    Pages (from-to)1-9
    Number of pages9
    JournalEnvironmental Research
    Volume188
    Early online date2 Jun 2020
    DOIs
    Publication statusPublished - 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).

    FundersFunder number
    National Key R&D Program of China
    National Natural Science Foundation of China41701571, 41701573, 41877500, 41977115
    Guangzhou Science and Technology Program key projects201904010116
    Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology2018K01
    National Key Research and Development Program of China2018YFD0800700, 2018YFC1800600
    Fundamental Research Funds for the Central Universities19lgpyl50

      Keywords

      • Bioavailability
      • Mixture
      • Rare earth
      • Toxicity
      • Triticum aestivum

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