The Environmental Chemical Sciences (ECS) program of the Division of Chemistry will support the collaborative RAPID research project of Prof. Thomas Bianchi of Texas A & M University, Prof. Robert Cook of Louisiana State University and Prof. Michael Perdue of Georgia Institute of Technology. The collaborative team will investigate the impact of oil contamination from the Deep Horizon Disaster in the Gulf of Mexico on the composition of dissolved organic matter (DOM) in the Louisiana coastal marshes. The study aims to prove that changes in the component signature of DOM collected from the Louisiana coastal marshes will be indicative of the impact of the Deep Horizon oil spill on geochemical processes in the Louisiana marshes. The team of investigators will utilize boats from the Louisiana Marine Universities Consortium (LUMCON), located in Terrebonne, LA to collect water samples from marshes along Terrebonne Bay. The samples will be filtered to collect the DOM from the water samples. Advanced analytical methods will be used to analyze the DOM content.
The study is crucial to elucidate the impact of the Deep Horizon oil spill on the ecosystems along the Louisiana coast. Better understanding of this impact is imperative to development of strategies to restore the marshes to their condition prior to the Deep Horizon oil spill disaster.
Approximately, 4.4 million barrels of light south Louisiana crude oil were released in the Gulf of Mexico by the Deepwater Horizon MC252 oil spill. A good amount of this oil found its way into Louisiana’s highly productive estuaries. There were concerns in regards to possible damage the spilled oil could have on these valuable estuaries, including the ecosystems that rely on them. Dissolved organic matter (DOM) is a basic component of these ecosystems and oil-induced changes in DOM could have consequences on the ecosystem’s health. This led to the following question: Did oil contamination lead to a change in the chemical composition of the DOM within contaminated estuaries?". In order to address this question, two different types of samples were collected. The first sample set consisted of 26 small volume grab samples. This sampling was done twice, on July 16 and on September 24 2010. At each sampling site, water quality parameters (temperature, salinity, and dissolved oxygen) were also measured. The small samples were filtered, to at least 0.45 microns, and then underwent a range of spectroscopic analyses, providing qualitative (DOM composition) data. In addition, total organic carbon (TOC) analysis was also obtained, giving quantitative (amount of DOM) data, while the spectroscopic analysis yielded qualitative (DOM composition) data. These data allowed for the monitoring of changes within the DOM pool. The filters used to filter the water for these samples were used for bacterioplankton community analysis. On aggregate, all the data from these small grab samples clearly show that the samples obtained in July and September were different, but no such distinct difference could be found for samples obtained near contaminated versus non-contaminated sites. The second set of samples consisted of four approximately 500-liter samples from two contaminated and two non-contaminated sites (contamination was determined by visual inspection). Still on the boat, these large 500-liter samples were serial-filtered down to 0.45 microns and then protected from light and kept as cold as possible during their storage and transport. These samples were then concentrated using reverse osmosis and electrodialysis and remaining water was removed by freeze drying to yield a solid form of the DOM. These DOM samples were then analyzed by three sophisticated methods capable of providing molecular level description of changes in the DOM’s chemical composition caused by oil contamination. These characterizations have now been completed, as has the initial interpretation of the collected data.
