Use of Three Different Nanoparticles to Reduce Cd Availability in Soils: Effects on Germination and Early Growth of Sinapis alba L.

Globally, cadmium (Cd) is one of the metals that causes the most significant problems of contamination in agricultural soils and toxicity in living organisms. In this study, the ability of three different nanoparticles (dose 3% w/w) (hydroxyapatite (HANPs), maghemite (MNPs), or zero-valent iron (FeNPs)) to decrease the availability of Cd in artificially contaminated agricultural soil was investigated. The effect of Cd and nanoparticles on germination and early growth of Sinapis alba L. was also assessed by tolerance/toxicity bioassays. The available Cd contents in the contaminated soil decreased after treatment with the nanoparticles (available Cd decreased with HANPs: >96.9%, MNPs: >91.9%, FeNPs: >94%), indicating that these nanoparticles are highly efficient for the fixation of available Cd. The toxicity/tolerance bioassays showed different behavior for each nanoparticle. The HANPs negatively affected germination (G(%): 20% worsening compared to control soil), early root growth (G(index): −27.7% compared to control soil), and aerial parts (Ap(index): −12%) of S. alba, but showed positive effects compared to Cd-contaminated soils (G(index): +8–11%; Ap(index): +26–47%). MNP treatment in Cd-contaminated soils had a positive effect on germination (G(%): 6–10% improvement) and early growth of roots (G(index): +16%) and aerial parts (Ap(index): +16–19%). The FeNPs had a positive influence on germination (G(%): +10%) and growth of aerial parts (Ap(index): +12–16%) but not on early growth of roots (G(index): 0%). These nanoparticles can be used to reduce highly available Cd contents in contaminated soils, but MNPs and FeNPs showed the most favorable effects on the early growth and germination of S. alba.