Study of the particle characteristics and stability of Ag-NPs naturally generated in soil matrix

Nano-silver (Ag-NPs) has been widely applied due to its antibacterial properties, but issues remain with its toxicity. Although most Ag-NPs in the environment come from artificial import, the natural generation of Ag-NPs has also been discovered. In the present study, the particle characteristics and stability of naturally generated Ag-NPs, which might be different in migration, transformation, and bioavailability of artificially introduced Ag-NPs, were investigated and discussed in detail. Cloud point extraction and single-particle inductively coupled plasma mass spectrometry were used in combination to quantitatively analyze the naturally generated Ag-NPs and further explore their particle characteristics and stability. The results showed that a conversion behavior of Ag+ to Ag-NPs existed in environmental soil, and the particle sizes of the Ag-NPs were mainly distributed in the 30–40 nm range. It was found that oxygen, illumination, and humic acid could promote the natural generation of Ag-NPs but had different effects on the stability of Ag-NPs. Ag-NPs could be generated and stabilized under the combined action of fulvic acid and humus. This could become a meaningful basis to deeply explore the toxicological effects of Ag-NPs and control Ag-NP pollution from different sources and provide a way to discuss the role and influence of trace metals in geochemical transformations.