Behavior of engineered nanoparticles in aqueous media
Engineered nanoparticles (ENPs) have been in use for decades and offer many valuable applications. Unfortunately, however, many ENPs are lost in wastewater and transferred to freshwater and marine environments. Little is known regarding the behavior and ultimate fate of ENPs in the aquatic environment. The purpose of the reported research was to examine the behavior of three conventional ENPs (Ag, TiO2, ZnO) and two innovative ENPs (BiVO4/Pd and Cu2O/Pd) in simulated aquatic environments. The ENPs were added weekly to 18-liter totes and PVC columns and incubated. After 15 weeks, water and sediment were analyzed for metal content. In a third study, cattail (Typha latifolia) was exposed to the five ENP types and metal uptake determined. In the totes, Cu concentrations of 0.46 mg/L and 97.2 mg/kg were measured in solution and sediment, respectively; Zn concentrations were 0.34 mg/L and 77.9 mg/kg in solution and in sediment, respectively. Concentrations of the other ENPs were negligible. In columns, Cu and Zn were fairly evenly distributed throughout the columns. In the Typha study, all nanoparticles (or component metals) were preferentially sequestered in root compared to shoot tissue. In many cases, root concentrations were more than ten-fold greater in roots compared to shoots. These data indicate that cattail may serve as an excluder of several ENPs. Continued study of nanoparticles in water and sediment is imperative in order to better understand the ultimate fate of these potentially hazardous materials. Furthermore, both aquatic and terrestrial plants must be studied in some detail in order to determine their potential for phytoremediation of ENP-affect water and soil.