The impact of silver sulfide nanoparticles and silver ions in soil microbiome

The use of biosolids as fertilizers in agriculture can lead to the exposure of soil biota to sulfidised silver nanoparticles (Ag2S NPs), generated during the wastewater treatment procedures. Considering the crucial role of microorganisms on soil functions, we aimed to study the effects of 10 mg kg-1 soil of Ag2S NPs or AgNO3 on the soil microbiome, using an indoor mesocosm. After 28 days of exposure, Ag2S NPs induced a significant change in the soil microbiome structure, at class, genera and OTU levels. For instance, a significantly higher abundance of Chitinophagia, known for its lignocellulose-degrading activity, was observed in Ag2S NPs-treated soil toward the control. Nevertheless, stronger effects were observed in AgNO3-treated soil, over time, due to its higher silver dissolution rate in porewater. Additionally, only the AgNO3-treated soil stimulates the abundance of ammoniaoxidizing (AOB; amoA gene) and nitrite-oxidizing (NOB; nxrB gene) bacteria, which are involved in the nitrification process. Distinct variants of amoA and nxrB genes emerged in silver-treated soils, suggesting a potential succession of AOB and NOB with different degree of silver-tolerance. Our study highlights the latter effects of Ag2S NPs on the soil microbiome composition, while AgNO3 exerted a stronger effect in both composition and functional parameters.