Atmospheric Distributions of Polycyclic Aromatic Hydrocarbons (PAHs) in Coastal Northern Gulf of Mexico, USA, Associated with the Deepwater Horizon Oil Spill

Abstract

The Deepwater Horizon (DWH) oil spill occurred April 20, 2010 to July 15, 2010, releasing a surface slick of crude oil extending to ~176,000 km² in the Gulf of Mexico (GOM). Crude oil is comprised of thousands of organic compounds, many of which are toxic or carcinogenic. There is concern that some petroleum-derived toxic and carcinogenic hydrocarbons from the DWH spill may have volatilized and transported landward to the Gulf Coast States. It is important to determine the fate of these oil-derived compounds since their landward transport and inhalation may compromise human health. Polycyclic aromatic hydrocarbons (PAHs) are one suite of organic compounds that have been used to fingerprint oil to identify its source. In this study, the relative abundance of 34 PAHs derived from the DWH spill were compared to those found in oil from natural seeps in the northern GOM and from various sources in the Santa Barbara Channel, CA. The PAH distributions of the DWH oil were also compared to PAH distributions in air and water samples collected from several coastal sites in the Gulf Coast States sampled in July, 2010 and July, 2011. Additionally, the distributions of PAHs in air and water samples were compared before and after passage of Tropical Storm (TS) Bonnie (2010) that traveled across the GOM in late July, 2010. Lastly, particulate organic carbon and black carbon (a combustion byproduct) were extracted from these air samples to provide more information on the sources of air masses in the region. The results from this study suggest that the DWH riser oil contained ~3,600 [mu]g g⁻¹ of total PAHs and an average ~500 [mu]g g⁻¹ of PAHs in the surface slick. 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, our results indicate that the marine-to-land transport vector was facilitated by passage of TS Bonnie across the DWH oil slick in July, 2010. For example, the total atmospheric PAH loading to window film (a passive air sampler) increased by a factor-of-fifty after the passage of the storm, and the TS Bonnie rainwater contained dissolved organic carbon with a ¹⁴C age of ~8,000 y BP. Together, these results suggest that marine-to-land atmospheric loading of organic carbon and contaminants may be important during tropical storms and hurricanes.