Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
The northern Gulf of Mexico and the coastal estuaries of south Louisiana have a history of contaminated sediments and their associated human and environmental impacts. Hydrocarbon chemical pollutants within five major estuaries of the Mississippi River watershed and three offshore shoaling regions were assessed. Ten polycyclic aromatic hydrocarbons (PAHs) and three toxic equivalencies served as benchmark toxicants to investigate the impacts to sediments collected in years 2012 to 2014. The samples were analyzed using gas chromatography/mass spectroscopy (GC/MS) methods to determine the concentrations of pollutants within the sediments. Relationships between the measured pollutants and associated environmental conditions, including salinity, organic matter, temperature, dissolved oxygen, and temporal and spatial variables, were determined. The most important physiochemical variables affecting PAH concentrations were sediment moisture and organic matter content. Year had a significant and negative effect on four of the ten quantified PAHs with concentrations decreasing over time. Eight of the thirteen measured constituents had concentrations that were significantly different between inshore and offshore sediments. Seven of the ten quantified constituents were significantly affected by seasonal variations; the fall season demonstrated significantly lower concentrations of the pollutants as compared to the spring and the spring season showed significantly higher concentrations of the pollutants as compared the summer. Six of the thirteen measured constituents were significantly different in terms of quantified concentrations of the pollutants between oiled and non-oiled sediment samples, based on Deepwater Horizon oil intrusion. In each instance, the concentrations of the pollutants in the sediments were greater at oiled sampling stations as compared to non-oiled locations. The Atchafalaya River transect had the highest predicted concentrations for nine of the thirteen measured constituents and seven out of thirteen showed offshore contaminant deposition at Ship Shoal due to the discharge of the Atchafalaya River. Lake Pontchartrain was the least polluted transect with the lowest predicted concentrations for seven of the thirteen constituents. This comprehensive research provides spatial and temporal data crucial for risk assessment and decision making concerning sediments in the Mississippi River delta ecosystem.
Document Availability at the Time of Submission
Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.
Basirico, Laura Marie, "Ecotoxicological Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in the Mississippi River Coastal Watershed and Offshore Shoaling Regions of the Northern Gulf of Mexico" (2017). LSU Doctoral Dissertations. 4220.