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Carboxymethylcellulose-modified nano-zero-valent iron (C-nZVI) promotes ryegrass phytoremediation of cadmium in sediments co-contaminated with multiple microplastics: Mechanisms revealed by PLS-PM
Summary
A study found that applying carboxymethylcellulose-modified nano-zero-valent iron (C-nZVI) to soils co-contaminated with cadmium and six types of microplastics significantly boosted ryegrass growth and cadmium uptake while stabilising the metal in a less bioavailable form in the sediment. The results suggest C-nZVI could help rehabilitate agricultural soils facing the increasingly common problem of simultaneous microplastic and heavy-metal pollution.
The widespread distribution of microplastics (MPs) presents new challenges for the remediation of toxic metals-contaminated sediments. In this study, carboxymethylcellulose-modified nano-zero-valent iron (C-nZVI) was applied to explore its potential to assist ryegrass (Lolium perenne L.) in remediating sediment co-contaminated with cadmium (Cd) and six different types of MPs. Experimental results indicated that application of C-nZVI not only increased total dry biomass (+0.81 % to + 58.94 %) and enhanced the overall length of plants (+2.57 % to + 30.94 %), but also improved their capacity for Cd accumulation (+4.76 % to + 69.49 %). Furthermore, C-nZVI significantly increased the residual fraction of Cd (+22.12 % to +148.67 %), stimulate sediment enzyme activities and increased the relative abundance of key bacterial taxa (such as Devosia and Nitrosomonas), which are functionally linked to nutrient cycling and toxic metal immobilization, thereby supporting the remediation process. The partial least squares path model revealed that C-nZVI regulated the sediment-ryegrass system via two effective pathways: it not only reduced the bioavailable forms of Cd and increased the residual forms of Cd, but also enhanced Cd uptake by plants and facilitated plant growth. This study demonstrates the promising application of C-nZVI in enhancing phytoremediation efficiency in complex pollution scenarios where toxic metals and diverse MPs co-exist. This nano-enabled strategy offers a practical solution for the in-situ remediation of polluted riverine or wetland sediments. Future research should focus on field validation and assessing the long-term ecological impacts of this approach.