Semester of Graduation

Spring 2018

Degree

Master of Science (MS)

Department

Environmental Sciences

Document Type

Dissertation/Thesis

Abstract

The Mississippi River watershed is the third largest in the world and drains from 31 states in the United States. Due to its route through the U.S., it passes through hundreds of EPA labeled Superfund sites as well as agricultural and suburban watersheds. These sites are known to have historical chemical contamination, and as a result chemicals can be transported by runoff down the Mississippi River into the Gulf of Mexico where their ultimate fate is unknown. Organochlorine chemicals are known to be persistent and are found in agricultural land as well as US EPA Superfund sites, especially DDT, PCBs, and endosulfan. Though these chemicals have been removed from the market for more then 40 years, they have been known to persist in soils and sediment and can potentially bioaccumulate up the food chain.

During August 26-September 7, 2016, scientists from multiple universities conducted a research cruise out of LUMCON in Cocodrie, LA and collected sediment cores in various locations in the Gulf of Mexico, ranging in depth from 17.5-49.5 meters. An additional core from ship shoal (6.5 meters in depth) was analyzed due to its location in relation to the Louisiana coastline. A method to analyze and quantify concentrations of legacy contaminants in marine sediment was developed using pressurized solvent extraction and GC/MS/MS. The method was very sensitive for these analytes with method detection levels (MDLs) ranging from 0.38-1.6 ng/g and limits of quantitation (LOQs) ranging from 1.22-5.1 ng/g in sediment samples, however instrument detection limits (IDLs) based on a lower limit of 3:1 signal to noise. Analytes were recovered from sediment samples with greater than 70% efficiency with maximum of 19% relative standard deviations (RSD). All analyte concentrations were below calculated MDL and LOQ limits, however IDLs were above the acceptable EPA limits with most analytes detected at trace levels in all samples. Spatial and temporal analysis of individual contaminant concentrations in samples indicated that there were no major differences between locations or depth of sediment cores collected.

Date

3-3-2018

Committee Chair

Armbrust, Kevin

Available for download on Tuesday, April 01, 2025

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