Effect of Silver Nanoparticles On Zebrafish and Bacteria in a Lab-Scale Constructed Wetland with Potential Remediation by Soil and Water Treatment Residuals.

With recent advancements in technology, nanoparticles are becoming more prevalent in everyday use. There are many unanswered questions about the fate of nanoparticles, such as where they end up in the environment and the possibility of bioaccumulation in plants and animals. The specific aim of this study is three-fold; 1) to determine the environmental impacts of silver nanoparticles in zebrafish, 2) to investigate the impacts of silver nanoparticles on bacteria, and 3) to concurrently investigate the potential remediation of nanoparticles by a constructed wetland via soil and water treatment residual adsorption.

To accomplish these goals, the researchers exposed adult zebrafish in a lab-scale constructed wetland to 15, 25, and 50 mg/L silver nanoparticles (<90 nm) and examined their structural characteristics after 7 days.  The zebrafish were euthanized, sectioned and their histology compared to control fish with no silver exposure as well as zebrafish with silver nitrate exposure. Additionally, the effects silver nanoparticles on the survival of Bacillus subtilis, (a common soil bacterium), Escherichia coli (an intestinal bacterium that enters wetlands from human waste), and various bacteria naturally found in wetlands was examined. Finally, silver nanoparticles were measured in the soil of the constructed wetland after the 7 day exposure. Separately, both a sorption and a desorption experiment were carried out examining a wetland soil (high organic matter), a silt loam, and a water treatment residual (mostly aluminum sulfate) in their ability to sorb and subsequently re-release silver nanoparticles. Previous research has studied the effects of silver nanoparticles on various organisms in laboratory settings; however this type of study does not represent environmental conditions. The results of this study will shed light on silver nanoparticles effect on organisms in a simulated natural setting and suggest possible mechanisms for their removal from water.