ATMOSPHERIC DISTRIBUTIONS OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN COASTAL GULF OF MEXICO ASSOCIATED WITH THE DEEPWATER HORIZON OIL SPILL, COASTAL GULF OF MEXICO, UNITED STATES

Previous research suggests that marine organic matter may be transported onto land via precipitation and storm events originating over marine systems. The 2010 Deepwater Horizon (DWH) disaster in the Gulf of Mexico (GOM) released a surface slick of crude oil extending to ~176,000 km². There is concern that some petroleum-derived toxic and carcinogenic hydrocarbons from the spill may have been transported landward to the Gulf Coast States via atmospheric processes. It is important to determine the fate of these oil-derived compounds since their landward transport via atmospheric processes, may compromise human health.

Polycyclic aromatic hydrocarbons (PAHs) are one suite of organic compounds that have been used to fingerprint oil. In this study, the relative abundance of ~34 PAHs specifically derived from the DWH spill were compared to those found in oil from natural seeps in the northern GOM, and the geographically-separated Santa Barbara Channel. The PAH signature of the DWH oil was then compared to PAH distributions in air and water samples collected from several coastal sites in the Gulf Coast States in the summer of 2010, and then again in the summer of 2011. Lastly, distributions of PAHs in air and water samples were compared before and after passage of a hurricane storm system that traveled through the Gulf of Mexico. The results from this study suggest that the DWH riser oil contained ~3,600 μg g^-1 of total PAHs with surface slicks averaging ~500 μg g^-1 of PAHs. Ambient level of PAHs in air and water collected from coastal areas of the GOM were similar between 2010 and 2011, despite the presence of the oil slick from the DWH spill. However, using the results from air sampling, and measurements of natural abundances of radiocarbon in rainwater, our results indicate that the marine-to-land transport vector was facilitated by passage of Tropical Storm (TS) Bonnie across the DWH oil slick in July, 2010. For example, the total atmospheric PAH loading to window film increased by a factor-of-fifty after the passage of the storm, and the TS Bonnie rainwater contained DOC possessing a ¹⁴C age of ~8,000 y BP. Taken together, these results suggest that marine-to-land atmospheric loading of organic carbon and contaminants may be important during stochastic events such as hurricanes.