Biomonitoring Polycyclic Aromatic Hydrocarbon Deposition on Citrus Leaves
Authors:Sylvine Deprele, Daisy Galindo, Ani Voskanian
Mentor:Sylvine Deprele, Professor of Chemistry, Mount St. Mary's College
PAHs (Polycyclic Aromatic Hydrocarbons) are of continuous concerns due to their impact on our environment and health. PAHs are part of a large family of compounds made of fused benzene rings, some of them being carcinogenic. These compounds are generated by combustion of materials and accumulate in polluted areas. Their hydrophobic properties prevent them from being easily biodegradable thus, their life spent and dispersion in our environment is high. We have been interested in mapping PAHs concentration in our local Brentwood area using citrus and magnolia tree leaves as bio-monitors. Three distinct areas were chosen for examination: a secluded mountainside, a busy main street, and an interstate freeway. We hypothesize that the leaves collected from the interstate freeway will have the highest quantities of PAHs due to emissions from car exhaust. Leaves were initially homogenized, sonicated in CH2Cl2 in presence of Na2SO4 anhydrous and filtered. The solution was subsequently concentrated and qualitatively analyzed using Gas Chromatography Mass Spectrometry. Standards were used to monitor the PAHs in our data. In our experiments we successfully extracted benzene and several PAH derivatives. Amongst them, we identified benzo (b) thiophene, a reactive compound involved in petroleum processes. In our quest to identify pure PAHs, we plan on modifying both our extraction and filtration processes. Using alternate solvents or solvent combinations (CH2Cl2, Hexane) coupled with a new extraction method by means of a Soxhlet extractor is currently under investigation. We also anticipate applying chlorophyll digests to our solution in hope of eliminating much of our background noise.