Diagnostic ratios of polyaromatic hydrocarbons for the identification of pollution sources in clams from Okwagbe, Delta State Nigeria

Abstract

Polyaromatic hydrocarbons (PAHs) are pollutants found in the environment. Their sources are anthropogenic and natural. Since clams are filter feeders, they can accumulate (PAHs) in their tissues providing vital tool for pollution source monitoring. This study investigated different pollution sources using diagnostic ratio of PAHs. Clams were collected from Okwagbe River, Delta State, Nigeria and analyzed for their polyaromatic hydrocarbon (PAH) contents. The sixteen (16) priority PAHs, including: 1-methylnaphthalene and 2-methylnaphthalene were determined in flesh and shells using gas chromatography. A mixture of acetone/dichloromethane/n-hexane was used for the Soxhlet extraction. The concentration of mean total PAHs was 2.495 μg/kg for flesh and 2.156 μg/kg for shell. The benzo(a)pyrene (B[a]P) of flesh was 0.210 μg/kg and 0.312 μg/kg for shells. These valves did not exceed the permissible limit of 6.0 μg/kg for benzo(a)pyrene and 35.0 μg/kg for PAHs. The isomeric ratio was used to find the sources of PAHs in flesh and shells. It showed the sources were petrogenic, pyrogenic and wood burning. Clams can be a tool for tracking pollution source identification and improve understanding of human activities on ecosystems.