Historic Reconstruction of Polycyclic Aromatic Hydrocarbon Pollution in Southwest Florida Coastal Sediments

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous organic contaminants and are known to be toxic, carcinogenic and mutagenic in nature. Thus, select PAHs are EPA listed priority pollutants and are regularly monitored in various environmental matrices. PAHs enter into the coastal-marine environments via atmospheric deposition, river discharge, coastal erosion, oil spills and natural oil seeps. Marine sediments are the ultimate sink of PAHs entering into the oceans where they are preserved for long time. Thus, a historic reconstruction of these sediments using ²¹⁰Pb-based sediment dating coupled with quantitative analysis of sediment-PAHs provide time-series information about the extent and magnitude of PAHs contamination. In the past several decades, the population of Southwest Florida has increased rapidly, however to the best of our knowledge, none of the previous studies have reported the effects of rapidly increasing population on PAH concentrations and accumulation in this region. In order to fulfill this knowledge gap, sediment cores collected from various Southwest Florida coastal locations were analyzed for 43 PAHs using a GC-MS/MS and ²¹⁰Pb-based sediment dating using a High-Purity Germanium (HPGe) gamma detector. The preliminary results suggest that the constant rate of supply (CRS) based sedimentation rates vary between 0.01 to 0.2 cm/yr, and concentration of total PAHs (∑PAH₄₃) vary between 6.2 to 267.3 ng/g of wet sediments. Similarly, the ²¹⁰Pb-based PAHs accumulation rates vary between 0.31 to 13.4 ng/cm²/yr. While the results vary among sampling stations, the PAH profiles in sediment cores generally indicated that the PAH levels were higher in the past (during ~1970-2000 AD) than the recent surficial sediments. The results from the present study will provide us with invaluable information on how urbanization and rapid population growth correlate and affect the sediment PAH concentrations and accumulation rates in the coastal-marine environments.