Synergistic Interaction of Diatomite and <i>Vallisneria natans</i> Enhances Cadmium Phytoremediation in Sediments

Heavy metal pollution in aquatic sediments is a persistent global challenge. While phytoremediation presents a green solution, its efficiency is often crippled by the very toxicity of the contaminants to the plants. Here, we demonstrate a synergistic strategy that overcomes this paradox by augmenting the submerged plant Vallisneria natans with magnesium hydroxide-modified diatomite (Mg(OH)2-DE). In a year-long microcosm study, this approach dramatically stimulated plant biomass by over 229% under high cadmium (Cd) stress, underpinning a system that achieved up to 92.22% Cd removal from sediments. Mechanistic investigations reveal a dual-action synergy: the amendment simultaneously enhances the bioavailability of essential nutrients (Fe, Mn, Zn, and P) to fuel vigorous plant growth and activates a potent antioxidant defense network, evidenced by a 51.25% reduction in the stress marker malondialdehyde. This enhanced physiological resilience directly translated to superior phytoextraction performance by promoting the upregulation of NRAMP metal transporters. Our work, where engineered minerals unlock a plant’s intrinsic detoxification capabilities, establishes a robust and sustainable paradigm for in situ remediation of heavy-metal-contaminated aquatic environments.