Year Established: 2013 Start Date: 2013-03-01 End Date: 2014-02-28
Total Federal Funds: $7,500 Total Non-Federal Funds: $17,808
Principal Investigators: Dong Chen
Abstract: Silver nano particles (NPs) are the largest and fastest growing category of nanotechnology-based medicines and consumer products. After the products are consumed, washed, or discarded, silver NPs can be released into the environment, especially to a natural water body like the Wabash River. Silver is reported to be highly toxic to some aquatic organisms and as an antibiotic may also damage or alter beneficial microbial communities in the environment. The Wabash River flows through 19 counties and receives large amounts of treated sewage or untreated storm sewage from many cities in Indiana. Silver can enter the river water either as nanoparticles, nanoparticle aggregates, or soluble ions. It is reported that the toxicity of silver nanoparticles is primarily related to the released Ag+ as the metal silver is oxidized by oxygen and then dissolved. However, considering the complex chemical background of natural surface water, the silver NPs can have complicated processes such as dispersion vs. aggregation, dissolution vs. precipitation, oxidation vs. reduction, and complexation with the background chemicals such as chloride, surfactants, dissolved natural organic matters, and soluble extracellular microbial products. These processes will affect the forms of silver, and thus its antimicrobial effects. Currently there are large gaps in knowledge about the aqueous chemistry on the toxicity of silver NPs. The objectives of this projects are to: i) synthesize and characterize silver NPs; ii) systematically investigate the solution chemistry on the release of Ag+ and the silver morphology; and iii) evaluate the microbial growth rate and activities in a synthetic solution and the upper Wabash River water with silver NPs. This research will help to better understand the behaviors of silver NPs in the environment of natural surface waters and help to model and predict their toxicity to microorganisms, the most abundant and vulnerable part in the aquatic ecological system.