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Stability and Aggregation of Silver and Titanium Dioxide Nanoparticles in Seawater: Role of Salinity and Dissolved Organic Matter
Citation:
Wang, H., Robert M. Burgess, Mark G. Cantwell, Lisa M. Portis, Monique M. Perron, F. Wu, AND Kay T. Ho. Stability and Aggregation of Silver and Titanium Dioxide Nanoparticles in Seawater: Role of Salinity and Dissolved Organic Matter. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 33(5):1023-1029, (2014).
Impact/Purpose:
In this study, the stability and aggregation of 30 nm diameter silver nanoparticles (AgNPs) capped with citrate and polyvinylpyrrolidone (PVP) (AgNP-citrate and AgNP-PVP) and 21 nm diameter titanium dioxide (TiO2) NPs was investigated in seawater for up to 240 h. The effects of seawater salinity and natural organic matter concentration were evaluated by measuring time dependent hydrodynamic diameters and zeta potentials. These findings expand our knowledge on the behavior of AgNPs and TiO2 NPs in seawater, and indicate that the fate of these NPs will be primarily to aggregate and precipitate into the sediments rather than remain in the water column for very long periods of time when released into the marine environment.
Description:
The behavior and fate of nanoparticles (NPs) in the marine environment is largely unknown and has the potential to have important environmental and human health implications. The aggregation state and fate of NPs in the marine environment is greatly influenced by their interactions with seawater and dissolved organic carbon (DOC). In this study, the stability and aggregation of 30 nm-diameter silver nanoparticles (AgNPs) capped with citrate and polyvinylpyrrolidone (PVP) (AgNP-citrate and AgNP-PVP) and 21 nm-diameter titanium dioxide (TiO2) NPs as affected by seawater salinity and DOC were investigated by the measurements of hydrodynamic diameters and zeta potentials. The added DOC (in humic acid form) stabilized the three types of NPs when the seawater salinities were ≤ 5 ppt, but the stabilizing effect of DOC was reduced by a higher salinity (e.g., 30 ppt). In addition, AgNP-PVP was more stable than AgNP-citrate in seawater under the same conditions, indicating NP surface capping agents and stabilization mechanisms govern the stability and aggregation of NPs. Statistical analysis showed that salinity is the most dominant in influencing the stability and aggregation of AgNPs and TiO2 NPs in seawater, followed by DOC. These findings expand our knowledge of the behavior of AgNPs and TiO2 NPs in seawater, and indicate that the fate of these NPs will be primarily to aggregate in the water column, precipitate and accumulate in sediments following release into the marine environment.
