Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
Crude oil from Deepwater Horizon Macondo oil spill is currently present in Louisiana coastal surface sediments and its effects on the coastal ecosystem are still being realized. Deposition of 2- and 3-ring PAHs (alkylated naphthalenes and phenanthrenes) on the exterior of Spartina alterniflora and Avicennia germinans leaves have been demonstrated in marshes impacted by Macondo spill. Whether these deposition events result from contaminated tidal water or volatilization followed by deposition onto the leaf surface has not been conclusively established. Measurements of PAH deposition on the leaf surface of black mangrove (Avicennia germinans) can provide important evidence of the mechanism of deposition since these plants are rarely submerged by tidal water. Study objectives were to quantify and observe the uptake mechanisms of PAH accumulation as a function of time, leaf age, and leaf fraction in mangrove leaves from a heavily oiled site at Bay Jimmy marsh in Barataria Basin, LA. PAHs did not accumulate over time or leaf age indicating diffusion and equilibrium processes dominated and occurred quickly. PAHs accumulated in the inner tissue of the leaf posing a potential for long-term internal cycling of PAHs in a sediment-vegetation-biota system. Semipermeable membrane devices (SPMDs) were utilized in air and marsh surface in the field as a simple analogue to investigate the transfer process. Higher correlations between leaves and SPMDs were observed for C1-naphthalenes than the other PAHs studied. The plant – air partitioning coefficient (KPA) for various PAHs in field contaminated mangrove leaves was quantified using an experimental partitioning apparatus and compared to respective KPA values calculated for Spartina alterniflora. All KPA coefficients were well below 8 which supports the dominant uptake process of air phase PAHs is equilibrium partitioning between the vegetation and the gas phase.
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Decell, Matthew, "Accumulation and Dynamics of Petrogenic PAHs on Leaves of Black Mangrove (Avicennia germinans)" (2017). LSU Master's Theses. 4550.