Polycyclic Aromatic Hydrocarbon Demographic
Mentor:Sylvine Deprele, Professor of Physical Sciences & Mathematics, Mount St. Mary's College
Polycyclic aromatic hydrocarbons (PAHs) encompass one class of airborne carcinogenic compounds that negatively affect our health on a daily basis. These compounds infiltrate our cells; creating DNA adducts and resulting in the alteration of DNA sequencing. The purpose of our research is to establish an overall demographic of PAH concentrations in the Los Angeles area through the bio-monitoring of evergreen tree leaves; specifically, the Italian Blue Cypress. Three distinct areas were chosen for examination: a secluded mountainside, a busy main street, and an interstate freeway. Our initial procedure was to mechanically homogenize the collected leaves and subsequently extract them with CH2Cl2 using sonication. The process was then followed by filtration and evaporation. The concentrated solution was then analyzed using Gas Chromatography Mass Spectrometry (GC/MS). In the environment, PAH concentrations are known to be in the nanogram level and unfortunately, using the previously described technics, we found that plant components such as chlorophyll derivatives, interfered greatly with our detection levels. Our mixtures were very complex and isolation of PAHs was impossible. After these preliminary results, we modified our extraction process to minimize the amount of compounds present in our extracts. Leaf samples were extracted without homogenization and the extract obtained after sonication was subsequently exposed to an acidic workup using 3M HCl, sat. NaHCO3 aq. and H2O. Such treatment allowed for a drastic cleanup of our solution and the successful identification of two PAHs: Naphtalene (r.t.= 10.6 min) and Phenanthrene (r.t.= 9.27 min). We are currently pursuing our investigations to establish an optimal extraction methodology valid on multiple tree species.