Distribution and diagenesis of trace metals in marine sediments of a coastal Mediterranean area: St Georges Bay (Lebanon)

Abstract

St-Georges Bay (Lebanon) is an open bay, to the Mediterranean Sea and it is exposed to numerous anthropogenic activities such as industrial effluents, non-treated wastewater discharge and maritime activities leading an increasing chemical contamination especially with trace metals. Contamination with trace metals (Cu, Cd, Co, Pb, As, Ag and Hg) and the influence of early diagenesis on their distribution are studied on both sediments and waters transect. For this purpose, sediment cores were collected, then treated under inert atmosphere to retrieve pore waters and solid fraction. The area appeared to be seriously impacted by the transport through Beirut River and/or by direct inputs, and the recent landscaping done with dumpsite material. The sediments showed a significant level of contamination. Element mobility was studied by selective extraction on sediments. The mobility of the studied trace elements from solid fraction to pore waters is controlled by Fe/Mn cycle and organic matter.

Anthropogenic activities influence the mobilization of trace metals and oxyanions in coastal sediment porewaters

“…The concentrations of As in Baltic Sea sediment porewater are comparable with our results, whereas V is even higher (van de Velde et al, 2020;Scholz and Neumann, 2007). The two studies in Mediterranean sediment porewaters present the lowest element concentrations for the European regions (EI Houssainy et al, 2020;Dang et al, 2015), while the study in Great South Bay, USA, indicates relatively high Ni and V concentrations (Beck et al, 2010), which is comparable to our results. But other element concentrations are much lower than in this study.…”

Heavy Metal Accumulation and Release Risks in Sediments from Groundwater–River Water Interaction Zones in a Contaminated River under Restoration

“…Chemical speciation analysis using the sequential extraction method indicated that except for Cd and Cu, all other heavy metals had a large fraction associated with Fe/Mn oxides (F3) for both river-bed and river-side sediments (Figure ). This phenomenon was attributed to the strong adsorption capacity of Fe/Mn oxides for heavy metals, , and potential incorporation of heavy metals into Fe/Mn mineral structures. ,, The operationally defined Fe/Mn fraction also included the heavy metals associated with sulfides because metal sulfides would dissolve and release heavy metals during the extraction process . TEM analysis was tried to reveal the physical associations of the heavy metals with Fe/Mn and S. The low concentrations of the heavy metals in the sediment samples, however, prevented unambiguous identification of such associations.…”