Nanomaterials effectively alleviate cadmium hazards in soil-plant systems: A meta-analysis

Soil cadmium (Cd) contamination is a non-negligible global environmental issue as it may threaten food security and human health through soil-plant interactions. Nanomaterials have a great potential to decrease Cd bioavailability and bioaccumulation, even though the effects have been inconsistent among various studies. Here we compiled data from 137 experiments on the remediation of Cd-contaminated soils by nanomaterials. The effects of experimental design, nanomaterial properties, soil characteristics, and plant attributes on Cd bioavailability and bioaccumulation under nanomaterials application were evaluated. Results showed that incorporating nanomaterials could reduce the bioavailability of Cd in soil by 45.3 % and the bioaccumulation of Cd in plants by 37.6 %. Composite and carbon-based nanomaterials showed the most notable Cd immobilization effects at low and medium application rates, respectively. Cd-contaminated soils with low sand content, neutral pH (6.5 < pH ≤ 7.5), high organic matter (>30 g kg^-1), and high cation exchange capacity (>20 cmol kg^-1) are more conducive to the efficacy of nanomaterials. Among the four plant tissues, the decrease in Cd accumulation in leaf (39.4 %) and grain (37.7 %) was significantly higher than that in root (31.8 %) and stem (23.3 %) after the application of nanomaterials. Compared to other plant families, nanomaterials significantly suppressed Cd uptake by 54.7 % of Brassicaceae plants. Additionally, the Cd bioavailability showed a significantly positive correlation with Cd accumulation in the root (R² = 0.46, p < 0.001), leaf (R² = 0.42, p < 0.001), and grain (R² = 0.13, p < 0.01). Overall, our results highlighted that nanomaterials are an effective solution to mitigate the hazards of Cd pollution in soil-plant systems.