This study investigated the effects of green-synthesized silver (Ag) and palladium (Pd) nanoparticles (NPs) on soil carbon mineralization under controlled incubation conditions (28 °C and costant moisture for 42 days). AgNPs and PdNPs were synthesized using extracts of Melia azedarach L. leaves and characterized by UV-Vis spectroscopy, SEM-EDS, FTIR, and XRD analyses. The nanoparticles were applied to two different soil textures (clay and sandy) at three concentrations (10, 50 and 100 mg kg⁻¹) to evaluate their impacts on microbial activity through carbon mineralization measurements over 42 days. The results indicated that carbon mineralization was generally higher in clay soils than in sandy soils, with the highest mineralization rate reaching 15.43% in clay soils compared to 10.21% in sandy soils. AgNPs exhibited stronger inhibitory effects on microbial activity than PdNPs, with the highest AgNP dose (100 mg kg⁻¹) reducing carbon mineralization rates to 7.79% in clay soil and 7.16% in sandy soil. Conversely, the addition of Melia azedarach leaves and extracts enhanced mineralization, likely due to the presence of easily degradable organic compounds. This study revealed a distinct soil structure dependent pattern, in which clay fractions provide a significant buffering effect against the toxicity of biogenic nanoparticles. These results indicated that the surface coating derived from Melia azedarach extract interacted with clay surfaces, potentially reducing the bioavailability of nanoparticles compared with sandy soils.
Ozdal et al. (Fri,) studied this question.