Distribution of trace metals, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in sediment cores from the Sicily Channel and the Gulf of Tunis (south‐western Mediterranean Sea)

Abstract

Under the framework of the IAEA's Technical Co‐operation project RAF7/004, international research cruises were carried out in 2004 to assess the distribution of radionuclides and micropollutants in the south‐western Mediterranean Sea. Sediments samples had variable concentrations of total aliphatic hydrocarbons and polycyclic aromatic hydrocarbons ranging from 0.2 to 1.8 µg g−1 and 26.9 to 364.4 ng g−1, respectively, in the Sicily Channel and from 0.7 to 2.8 µg g−1 and 14.7 to 618.1 ng g−1, respectively, in the open sea of the Gulf of Tunis. Hydrocarbon concentrations changed with depth and were relatively high at 3 cm and 10 cm depths. The use of ‘fingerprint’ ratios of certain isomeric pairs of polycyclic aromatic hydrocarbons (PAH) and the proportion of 2–3 ring and 4–5 ring PAH concentrations showed that the main origins are characteristic of petroleum sources. The ranges of trace metal concentrations, expressed in µgg−1, in the Sicily Channel and in the Gulf of Tunis, respectively, were: Hg 0.009–0.2 and 0.02–0.1; Pb 9.9–26.1 and 21.2–32.5; Cd 0.06–0.1 and 0.07–0.33; Fe 23.7–28.1 and 29.9–36.2p; Zn 83–99.5 and 83–104; Mn 309.2–752.5 and 651–814; Cu 17.1–18.5 and 33.5–51.3. Sediment metal abundances were in the order: Mn > Zn > Fe > Cu > Pb > Cd > Hg. The results showed significant differences (p < 0.001) for trace metal and hydrocarbon mean concentrations between the two cores. These concentrations are generally similar to the background levels from the Mediterranean Sea and could be affected by physico‐chemical conditions and sedimentation rate as well as biodegradation.