Synergistic Effects of Silicon and Ferrous Sulfate on Reducing Arsenic and Cadmium Accumulation in Rice from Co-Contaminated Soil
The co-contamination of arsenic (As) and cadmium (Cd) in paddy soils threatens rice safety, yet synergistic mitigation strategies using silicon (Si) and ferrous sulfate (FeSO<sub>4</sub>) remain underexplored. This study integrated hydroponic and soil pot experiments to evaluate Si-FeSO&...
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| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Agronomy |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4395/15/6/1422 |
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| Summary: | The co-contamination of arsenic (As) and cadmium (Cd) in paddy soils threatens rice safety, yet synergistic mitigation strategies using silicon (Si) and ferrous sulfate (FeSO<sub>4</sub>) remain underexplored. This study integrated hydroponic and soil pot experiments to evaluate Si-FeSO<sub>4</sub> interactions on As/Cd accumulation and rice growth. Hydroponic trials employed 21-day-old rice seedlings exposed to 0.5 mg As(III)/Cd(II) L<sup>−1</sup> with/without 70 mg Si L<sup>−1</sup> and 30–70 mg Fe L<sup>−1</sup>, followed by sequential harvesting at 14 and 21 days. Soil experiments utilized co-contaminated paddy soil (50 mg As kg<sup>−1</sup> and 1.2 mg Cd kg<sup>−1</sup>) amended with Si (80 or 400 mg kg<sup>−1</sup>) and Fe (100 or 1000 mg kg<sup>−1</sup>), with pore water dynamics monitored over 120 days. Hydroponic results demonstrated that 70 mg Si L<sup>−1</sup> combined with 30 or 70 mg Fe L<sup>−1</sup> enhanced shoot biomass by 12–79% under As stress, while simultaneously reducing shoot As concentrations by 76–87% and Cd concentrations by 14–33%. Iron plaque induced by FeSO<sub>4</sub> exhibited contrasting adsorption behaviors: hydroponic roots immobilized both As and Cd (<i>p</i> < 0.01), whereas roots in soil primarily retained Cd (<i>p</i> < 0.05). In soil experiments, the optimal treatment of 100 mg Fe kg<sup>−1</sup> and 400 mg Si kg<sup>−1</sup> (Fe<sub>1</sub> + Si<sub>2</sub>) increased grain biomass by 54%, while reducing As and Cd concentrations by 37% and 42%, respectively. However, a higher Fe dosage (Fe<sub>2</sub>: 1000 mg kg<sup>−1</sup> Fe) paradoxically increased grain Cd concentrations. Mechanistically, Si amendment elevated soil pH (Δ + 0.72), facilitating Cd immobilization, while FeSO<sub>4</sub> lowered pH (Δ−0.07–0.53), increasing Cd mobility. A strong correlation between soluble Cd and plant uptake was observed (<i>p</i> < 0.01), while changes in As accumulation were unrelated to aqueous behavior. The optimized Si/Fe molar ratio of 7.95:1 effectively mitigated As and Cd co-accumulation, offering a dual-functional strategy for safe rice cultivation in contaminated soils. |
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| ISSN: | 2073-4395 |