Silver-containing nanoparticles shift microbial communities in estuarine sediments: Adaption to particle number concentration and size

The eco-behavioral mechanism of metal-containing nanoparticles (NPs) primarily focuses on the total concentration of metals, with little attention paid to their number concentration and size. In this study, the number concentration and size of Ag-NPs and dissolved Ag in sediments were detected based on the single particle (SP)-ICP-MS technique, and further explored their effects on microbial community in estuarine microcosms with treatments of zero-valent silver nanoparticles (Ag-0-NPs) and Ag+ at 10 mu g/L. Numerous Ag-NPs (e.g., Ag-0-NPs and Ag2S-NPs) were identified in sediments exposed to Ag-0-NPs and Ag+ based on electron microscopy techniques. The number concentration of Ag-NPs increased two orders of magnitude during this 30-days exposure period, and followed the order of low- > middle- > high-tidal flats. After 30 days exposure to Ag-0-NPs and Ag+, the number concentrations of Ag-NPs were 6.4 x 10(5) and 1.1 x 10(6) particles/mg in sediment collected from low tidal flat, with average sizes of 35 and 41 nm, respectively. Proteobacteria was the dominant phylum in response to Ag-0-NPs and Ag+, with an increase of 27 % and 15 %, respectively. The number concentration and size of Ag-NPs were more strongly correlated with the microbial composition than the dissolved Ag concentration. Moreover, significant correlations between particle size and cell mobility gene and dsrB abundance were found. Overall, our studies emphasize SP-ICP-MS is a novel and valuable technique for quantifying Ag-NPs, and highlight the importance of the number concentration and size of metal-containing NPs in the ecological risk evolution of microorganisms in estuarine environments.