Semester of Graduation

Fall 2019

Degree

Master of Civil Engineering (MCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

During crude oil spill events, vegetation in marsh environments sequester polycyclic aromatic hydrocarbons (PAHs) from the crude oil by partitioning from the air phase through the waxy cuticle on the leaf surface. Recent studies from Macondo oil-impacted marshes have demonstrated that cycling of low molecular weight petrogenic PAHs occurs through the cuticle and other leaf tissue. At present, our understanding of how PAHs travel through the cuticle is coarse and limited by grab samples across the entire leaf, which preventing a full understanding the dynamics of PAH cycling in this environment. Multiphoton (MP) confocal microscopy visualizes the distribution of PAHs that fluoresces between 350 and 390 nm across the leaf tissue 2-D depth of S. alterniflora and A. germinans. This study uses imaging and the observed fluorescence to quantify and compare with GC-MS measurements of specific PAHs. These images provide further evidence that the cuticle serves as the entry point of PAHs into leaf tissue. Additionally, spike recovery experiments on leaf tissue of S. alterniflora and A. germinans were conducted under field conditions to understand the dynamics of PAH cycling on leaf tissues with phenanthrene displaying an initial uptake with a decline within a two days. SEM imaging revealed the anatomy of the leaf surface with salt glands on A. germinans and ridge features on S. alterniflora. The leaf rinse water from both species had similar ion and nutrient concentrations with the highest being sodium and sulfate. Results from this study contribute to an understanding of where phenanthrene in transported to within the leaf tissue such as through the apoplasm in A. germinans and the symplasm in S. alterniflora. PAHs partitioned more readily in the 10ºC isotherm than in the 30°C isotherm in both A. germinans and S. alterniflora. Results from this study contribute to an understanding of not only PAH tracking techniques used in marshes, but also the timeline needed for effective implementation.

Date

8-19-2019

Committee Chair

Pardue, John H.

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