A POTENTIALLY OVERLOOKED FRACTION OF DEEPWATER HORIZON OIL IN SALT MARSHES?

The Deepwater Horizon (DwH) spill of 2010 oiled over 800 km of Gulf Coast salt marshes. Continual monitoring and detection of spilled oil in salt marsh sediments is critical to fully understand its effect and ultimate fate. Typically, spilled oil is quantified using a suite of indicator compounds prevalent in crude oil. Traditional monitoring methods focus on saturated and aromatic hydrocarbons, which are non-polar compounds. Between the time when the oil was released at the wellhead and deposition on the beach, Deepwater Horizon oil was chemically transformed, from dominantly saturated and aromatic hydrocarbons to more polar compounds. Yet, it is unknown if this chemically transformed oil is residing in salt marsh sediments. Salt marsh sediments, from both heavily oiled and non-oiled sites on the same marsh platform, were collected from extensively studied sites in Barataria Bay, LA in September, 2015. To assess the abundance of weathered oil in oiled and non-oiled sediments, the solvent extractable organic matter was separated into three broad chemical classes: saturated, aromatic, and polar compounds using silica gel chromatography. Distribution of organic matter and carbon into separated classes will be measured both gravimetrically and manometrically using closed tube combustion. Distribution of compound classes between oil and non-oiled marsh sediments will be presented. Results of this investigation aim to determine if chemically altered DwH oil is potentially being overlooked and is present in salt marsh sediments, in order to better understand its impact and ultimate fate.