Determination of PAHs in Surface Sediments along Dakar Coast Using QuECHERS and Gas Chromatography Coupled to Tandem Mass Spectrometry

Abstract

Untreated sewage, which is a source of many pollutants, can also deposit a mass of sediment on beaches. These sediments can trap many pollutants, including PAHs, which are toxic and mutagenic to DNA and RNA in organisms. In this study, we investigated the contamination of sediments from the beaches of Hann, Soumbédioune and Ngor on the coast of Dakar by the 16 priority PAHs identified by the US Environmental Protection Agency (EPA). The sediment samples were taken between June and September 2018. Analyses were carried out using the GC-MS technique in tandem mode. For extraction and purification, QuECHERS and dSPE RESTEK salts were used, respectively, with recoveries ranging from 83.87 to 98.10%. For PAH repeatability, the %RSD values ranged from 0.02 to 3.08%, while those obtained for reproducibility varied from 0.01 to 1.29%. The results show that the highest levels were recorded in September: pyrene with 35.763 µg.Kg-1, benzo(a)anthracene (22.396 µg.Kg-1) and benzo(k)fluoranthene (18.678 µg.Kg-1) in Hann. At Soumbédioune, dibenzo(a,h)anthracene is at 15.782 µg.Kg-1 and at Ngor coronene has the highest content (9.030 µg.Kg-1). Analysis of the Shapiro-Wilk normality test reveals that most of the p-values for the variances of the various PAHs are above the 5% threshold. For the Levene test, apart from pyrene, the rest of the hydrocarbons satisfied the heteroscedacity hypothesis (inequality of at least two variances) with p-values below the 5% threshold.