Contamination Levels and Accumulation Profiles of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediments from South Central Coast of Vietnam

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants of great concern due to their negative impacts on environmental and human health. The less polar and hydrophobic nature of PAHs is responsible for their ability to adsorb onto suspended particles and to accumulate in sediments. In this study, surface sediment samples were collected in the South Central Coast of Binh Dinh Province, Vietnam to determine concentrations of 16 PAHs. The sediment samples were directly ultrasound extracted with a mixture of acetone/hexane (1:1) and toluene. The extract was purified on a chromatographic column containing activated silica gel with dichloromethane/hexane (1:3) as elution solvent. PAHs were separated and quantified on a gas chromatography/mass spectrometry (GC/MS) system with a DB-5ms column. The MS detector was operated in electron impact ionization (EI) mode and ion selective monitoring (SIM) mode. Levels of 16 PAHs ranged from 33.1 to 196 (mean 80.0) nanograms per gram sediment (ng/g). In all sediment samples, proportions of high molecular weight PAHs (4-6 rings, 63–88%) were higher than those of low molecular weight PAHs (2-3 rings, 12–37%), indicating that emission sources are mainly related to thermal processes rather than petroleum products. The most predominant substances were: Pyr (14% ± 3%), Flt (12% ± 3%), Phe (10% ± 3%), Chr (9% ± 2%), and BaP (9% ± 3%). Further studies on the pollution status of PAHs and their derivatives in Vietnamese marine environments are essential.