ENVIRONMENTAL PROPERTIES AND IMPACTS OF NANOPARTICLES IN URBAN LANDSCAPES OF THE MIDWEST: MICROSCOPY STUDIES OF STREET SEDIMENT DEMONSTRATE CAUSE FOR CONCERN

Numerous nanoparticles are recognized as having high potential for inhalation and ingestion and abundant toxicology literature exists identifying associated health hazards. Nanoparticles generated by human activity in urban areas are of particular concern. They often are composed of toxic metals and are often concentrated in street sediment. Many of these pollutants have direct or indirect connections to geologic resources such as fuel use and metal production. Detailed studies of these nanoparticles to constrain the variation in street sediment using advanced techniques are uncommon. Street sediment is an important environmental medium because the fine sediment fraction may undergo wind dispersion and redeposition in soils. Inhalation of these nanoparticles by adults and children is a primary concern. Both Human and ecological health may be impacted when contaminated street sediment enters water bodies via storm sewers. Transmission electron microscopy (TEM) and field emission electron microscopy (FESEM) combined with inductively coupled plasma – optical emission spectroscopy (ICP-OES) and inductively coupled plasma – mass spectrometry (ICP-MS) conducted on street sediment from Gary, Indiana, Hamilton, Ohio, and Middletown, Ohio reveal a diversity of nanoparticulate pollutants in the Midwestern U.S. Nanoparticulate pollution occurs in two modes: (1) discrete anthropogenic metal, oxide and glass particles and (2) natural phyllosilicate and oxide particles with adsorbed, catalytically precipitated, or intermixed anthropogenic metals. Metal particles such as Pb, Zn, Cu, and W, lead chromate that is likely derived from traffic paint, a variety of coal spherules occurring in a range of preservation states, and transition metal oxide materials of variable texture and compositions are common. TEM techniques using nanoscale energy dispersive spectroscopy mapping indicate that illite, chlorite, and goethite components of sediment can have adsorbed Cu, Zn, Hg, and other metals as well as P. Results indicate that street sediment is an underappreciated mixed geologic – anthropogenic environmental medium. TEM and SEM combined with bulk geochemical techniques show immense promise in understanding the transport and fate of nanoparticulate pollutants and provide constraints for remediation.