ANALYSIS OF HEAVY METAL AND OTHER CONTAMINANTS IN STREET SEDIMENT FROM BOULDER CITY, NEVADA

Road sediment is a media that records both anthropogenic and geogenic materials making it a useful material to examine for environmental analysis globally. However road sediment studies in arid and semi-arid regions in the United States are uncommon. To address this, ten street sediment samples were collected from Boulder City, NV which is located southeast of Las Vegas, NV. Samples were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and handheld X-ray fluorescence (XRF). Our multi-method approach provides critical information regarding particle size, type, morphology, and elemental concentrations which helps to identify areas of greatest environmental concern.

SEM data has shown multiple heavy metal bearing particles present in samples in addition to other non-heavy metal particles such as rare earths, naturally occurring asbestos (NOA) fibers, and anthropogenic spherules. Some of the heavy metals present include lead, manganese, copper, and zinc. Iron-oxide particles appear to be associated with the heavy metals to some degree. TEM data supports SEM data showing the presence of Mn, Zn, Cr, and Ti in particles. XRF data shows that Cu and Zn correlate to some degree. Other modest correlations include Fe and As as well as Mn and As. Heavy metal particles and spherules are typically indicative of industrial pollution which is most likely from industrial and vehicular activity. Because the area is a semi-arid to arid environment, the transport and redistribution of road sediment and pollution by wind is more common than in other environments.

Further research is needed to determine the cause of correlation of Fe-oxide particles to heavy metals. Identification of possible sources of industrial pollution is also needed to fully understand the origin of contaminants and the distances the pollution particles traveled.