Examining the Soils Adjacent to the Historical Pitch Lake for Levels of Polycyclic Aromatic Hydrocarbons (Pahs) and Naturally Occurring Pah-Degrading Bacteria
American Research Journal of Earth Science
The soils adjacent to the La Brea Pitch Lake in Trinidadare expected to have high levels of Polycyclic Aromatic Hydrocarbons (PAHs) and PAH-degrading bacteria. This is due to the historical influx of hydrocarbons (bitumen) since the Cretaceous period. The PAHs are toxic, carcinogenic and genotoxic compounds which are natural components found in bitumen and natural oil seepages. This study investigates the occurrence of five selected PAHs (viz. naphthalene, acenaphthene, anthracene, phenanthrene
... and pyrene) andthe presence of bacteria that can utilize these selected PAH in soils neighbouring the PitchLake. To do this, soil samples from three distance zones to the perimeter of the Pitch Lake (zone 1: within 200 m; zone 2: within 400m and zone 3: >500m) were analyzed for levels of five selected and screened for their degrading bacteria using selective enrichment procedures. The results showed that the levels of these individual PAHs were generally above the standard acceptable limit of 1mg/Kg among all 3 zones except for anthracene in Zone 2. The levels of the total PAHs (∑5PAHs) showed a general trend of decreasing concentrations with high variability as thedistance from the Pitch Lake increased.The results of the soils screened for potential PAH-degrading bacteria showed that isolates in zone 1 and 2 (HIS) produced more PAH degraders for the more recalcitrant PAHs (viz. phenanthrene, anthracene,and pyrene) compared to naphthalene and acenaphthene, which bothappeared independent of zones.