Bioavailability and assessment of heavy metal pollution in sediment cores off the Mejerda River Delta (Gulf of Tunis): How useful is a multiproxy approach ?

Mohamed Amine Helali (1) , Walid Oueslati (1) , Noureddine Zaaboub (2) , Ayed Added (1) , Lotfi Aleya (3)

1 FST - Faculté des Sciences Mathématiques, Physiques et Naturelles de Tunis
2 INSTM - Institut National des Sciences et Technologies de la Mer [Salammbô]
3 LCE - Laboratoire Chrono-environnement (UMR 6249)

Three core samples were taken from zones offshore from the Mejerda River Delta (Tunisia) and analyzed for major and trace elements to assess their relationships with organic matter, monosulfides and carbonates, as well as for pollution and bioavailability. Chemical speciation,ΣSEM/AVS, the enrichment factor (EF) and the geo-accumulation index (I-geo) were used. Iron, cadmium, lead and zinc – the most frequently mined metals in the Mejerda catchment – were found as contaminants in the offshore areas. Estimations of trace element accumulation using the EF and the I-geo index show that lead, and to a lesser extent zinc, are the most polluting metals off the Mejerda outlet. According to their bioavailability, these metals are also the most toxic. Only cadmium is heavily present in delta sediment (EF N 100) though deeply sequestrated (100% bound to the residual fraction) and thus presents no toxicity.

Mots clés: Chemical speciation; Coastal areas; Enrichment factor; Geo-accumulation index; Toxicity

Domaines: Sciences de l'environnement

Mohamed Amine Helali, Walid Oueslati, Noureddine Zaaboub, Ayed Added, Lotfi Aleya. Bioavailability and assessment of heavy metal pollution in sediment cores off the Mejerda River Delta (Gulf of Tunis): How useful is a multiproxy approach ?. Marine Pollution Bulletin, 2016, 12 p. ⟨10.1016/j.marpolbul.2016.02.027⟩. ⟨hal-01277537⟩