THE FIRST METAL POLLUTION INVESTIGATION OF ROAD SEDIMENT FROM BOQUERÓN, A COASTAL COMMUNITY IN WESTERN PUERTO RICO

Road sediment is fundamentally a mixture of anthropogenic and geogenic materials and a variety of studies exist in the U.S. however there is a paucity of road sediment investigations in coastal settings. Road sediment investigations can serve as important environmental surveys for metal pollution in communities. One region of the U.S. which has no road sediment pollution investigations and has extensive coastal communities is Puerto Rico. Boquerón is a tourist destination located in southwest Puerto Rico and is adjacent to the Parque Nacional Balneario Boquerón. This location provides an excellent setting to evaluate road sediment because the surficial background sedimentary material is carbonate sand, enabling straightforward identification of metal particulates and anthropogenic particles in scanning electron microscopy. Background sediments are characterized by carbonate grains of a variety of biogenic materials with lesser amounts of diatoms. Sands have an average grain size of approximately 500 micrometers. Initial scanning electron microscopy (SEM) data on road sediment samples indicates the presence of zinc and lead in diffuse elemental maps and is interpreted to reflect dissolution - reprecipitation or adsorption from vehicle derived particulates. SEM identified chrysotile asbestos in one sample where the particle appears to be mat-like and is interpreted as a degraded asbestos product. The source of the asbestos is unclear and may be automotive or construction related. Metal and asbestos pollution is evident in road sediment and is not completely flushed from the road system, even with comparatively high precipitation in the area. Results of this initial study provide constraints for understanding the transport of pollution into the nearby marine environment, including context for potential future metal isotope tracing studies.