Uptake and Deposition of Pyrogenic and Petrogenic PAHs on Spartina Alterniflora

Abstract

Saline marshes dominated by Spartina alterniflora were impacted by MC252 crude oil along Louisiana’s shoreline. Two locations were evaluated in this study; a lightly oiled, saline marsh near Port Fourchon, LA and a less saline, heavily oiled marsh near Bay Jimmy in the Barataria Basin, LA. Objectives of this study were to develop a method to extract polycyclic aromatic hydrocarbons (PAHs) from Spartina leaves and to compare and contrast the relative uptake and deposition of petrogenic and pyrogenic PAHs in Spartina leaves. A three-step sequential extraction procedure was developed for the extraction and analysis of PAHs on Spartina leaves. In the field, particles deposited on the leaf were dissolved in EDTA solution, and the leaf cuticle was dissolved in dichloromethane. PAHs were quantified in selective ion monitoring mode using a gas chromatograph connected with a mass selective detector. A controlled experiment was also performed in a greenhouse to determine the partition coefficients between air and Spartina plant surfaces. Samples collected from Fourchon Beach were extracted, and results demonstrated the presence of both naphthalenes and phenanthrenes in the Spartina leaves. In general, Fourchon Beach samples, where the water was, more saline and displayed a lower concentration of PAHs in the Spartina leaves. Bay Jimmy samples, where the water was less saline included a higher concentration of PAHs. The concentration of naphthalenes was higher than that of the phenanthrenes. Samples from Bay Jimmy were collected three times, Summer 2013, Winter 2013, and Summer 2014. The samples from summer 2013 included a high concentration of phenanthrenes. Naphthalenes were present but in low concentrations. The Bay Jimmy winter 2013 samples were consistent with the summer 2013 samples in that the phenanthrenes were present, however, the naphthalenes were present in a higher concentration. The winter 2014 samples continued to show a high concentration of phenanthrenes and an even higher concentration of naphthalenes. In both sampling locations, the PAHs present were dominantly in the cuticle and the tissue of the Spartina leaves. These results were consistent with those recovered in the control experiment. The plant leaves in the experiment displayed the same results.