SCANNING ELECTRON MICROSCOPY - ENERGY DISPERSIVE SPECTROSCOPY (SEM-EDS) INVESTIGATION OF ROAD SEDIMENT NEAR A PETROCHEMICAL PLANT, PEÑUELAS, PUERTO RICO

Road sediment is a unique and complex environmental media that can provide insights into pollution in various communities. Petrochemical manufacturing plants are sites that may require extensive environmental monitoring owing to the size and complexity of the systems present. Road sediments associated with petrochemical plants have not been specifically investigated in the U.S. One region of the U.S. which has no prior road sediment pollution investigations and has some petrochemical manufacturing plants is Puerto Rico. Whether or not metals that may be associated with petrochemicals such as V and Mo, and anthropogenic particles such as technogenic spherules can be identified and sourced to petrochemical plants is unknown. Local marine volcaniclastic rocks are located north of the plant, and whether or not complex particles with mafic mineralogies can be traced to these rocks is unclear. Eighteen (18) samples of road sediment were collected to assess the nature of pollutants in these materials. Initial scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS) analysis reveals an array of spinels with variable concentrations of Fe, Mn, Ni, Cr, and V. Other metals are observed in particles including Cu, Ag, Zn, W, and Ba. Although spinel sizes (<2.5 micrometers) and compositions are consistent with what could be expected from pollutants, a background origin cannot be ruled out. One particle (10 micrometers in diameter) exhibits a fine hackly texture consistent with an alloy of Ni, Cr, and Fe, representing a steel fragment that has not been transported far from its source. Barite is common, and likely originates from white road paint. One example of barite contains Cu, representing a complex anthropogenic product from another source. Spherules of various compositions and sizes are degraded, consistent with what could be expected from exposure to a tropical environment. This diverse suite of anthropogenic and geogenic particulates warrants further analysis and opens several questions regarding the occurrence of hazardous metals in the environment.