The nature and distribution of road sediment contaminants in the greater Las Vegas, Nevada area

Road sediment is an underutilized medium in the investigation of environmental pollution, yet it serves as both a source and sink for a wide array of pollutants. In urban areas especially, contaminants present within road sediment have the potential to pose human health risks depending on the abundance, chemical, and physical nature of these contaminants as well as the duration (i.e. acute or chronic) of exposure. Las Vegas, Nevada is currently one of the fastest growing urban areas in the United States and is therefore a prime location for the investigation of potential environmental contaminants and pollutants in road sediment. Forty-six road sediment samples were collected from locations throughout the Las Vegas region, including Las Vegas, Henderson, and Boulder City. Geochemical and mineralogical characterization of the selected samples was completed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray fluorescence spectrometry (XRF). Results from these analyses indicate the presence of metal-bearing particulate matter (including metal shavings), in addition to spherules, all of which are consistent with an anthropogenic origin. Additionally, geoaccumulation index (I_geo) values determined from XRF bulk chemical data show that Cu and Zn were enriched in road sediment samples (I_geo > 1) throughout Las Vegas and are thus considered to be significant anthropogenic pollutants in the region. This study serves as the first investigation into road sediment contaminants in the region, and provides a critical framework for more detailed investigation of the source and potential human health effects of these contaminants.