How useful are geochemical and mineralogical indicators in assessing trace metal contamination and bioavailability in a post-restoration Mediterranean lagoon?

Abstract

Tunis's Lake North (LNT), located on the Mediterranean Sea, and Tunisia's most important lagoon due to its economic value and its strategic position within the city, has recently undergone a vast sanitation project. To study the lagoon's level of metal pollution, three sediment cores were taken and the sediments were analyzed for trace and major elements, acid volatile sulfides (AVS), total organic carbon (TOC), and minerals. Results showed that TOC concentrations (0.2-3.1%) decreased following the lagoon's restoration. In addition, in comparison to historical data, concentrations of Cu (16-69.5 μg g), Zn (60.6-191.4 μg g), and Pb (13-100.9 μg g1) also decreased. Enrichment factor calculation with respect to the crust and local background showed that the sediment had long been contaminated by human pollution and especially by Pb, Zn, and Cu. The AVS to simultaneously extracted metal (SEM) ratio revealed values generally less than 1 indicating no sediment toxicity risks. Statistics revealed a detrital origin for certain metals and a diagenetic origin for FeS and carbonate minerals.

Assessment of trace metal contamination and phosphorus dynamic in sediments of Monastir Bay (Tunisia)

“…The zinc concentrations are similar to those of the Sfax coast (39 -117 ppm) but seem much lower than those of the Gabes coast in 2013 and the Gulf of Tunis where the maximum values reach 7165 ppm and 451 ppm respectively. The total phosphorus concentrations in the surface sediments of the Bay of Monastir vary between 300 and 643 µg/g (Table 1), values in the ranges of those measured in other coastal ecosystems in Tunisia: Tunis Lake and the Korba [30] or Bizerte Lagoons [26]; but much stronger than in other Mediterranean coastal ecosystems in Italy (397 tot. P µg/g, [35]) or in Greece (205 tot.…”

Soil Organic Carbon and Carbonates are Binding Phases for Simultaneously Extractable Metals in Calcareous Saltmarsh Soils

“…On the other hand, due to the low Fe content of the parent mineral matrix, larger concentrations of Fe in anoxic soils may result from accumulation of water-borne Fe, which precipitated as mackinawite or pyrite (Rickard and Morse 2005). This phenomenon strongly depends on low Eh conditions (Berner 1981), because fine marine sediments are commonly enriched in Fe sulfides (Oueslati et al 2018). Pyrite and mackinawite formation could also support the positive relationship recorded between Fe and total PTEs in soil, considering that trace metals and toxic elements could be trapped by the precipitation of minerals during pyritization (Huerta-Diaz and Morse 1992).…”

“…On the other hand, due to the low Fe content of the parent mineral matrix, larger concentrations of Fe in anoxic soils may result from accumulation of water-borne Fe, which precipitated as mackinawite or pyrite (Rickard and Morse 2005). This phenomenon strongly depends on low Eh conditions (Berner 1981), because fine marine sediments are commonly enriched in Fe sulfides (Oueslati et al 2018).…”

“…The risk of PTE transfer to benthic and aquatic organisms is often assessed using the molar ratio of SEM to AVS (∑SEM/AVS) in both freshwater (e.g., Cardoso‐Silva et al ; Li et al ) and saltwater systems (Younis et al ; Zaaboub et al ; Silva et al ; Oueslati et al ; Pignotti et al ).…”

Estudio de la dinámica sedimentaria de la Laguna costera del Sur de Túnez (Túnez, Mar Mediterráneo)

“…The prevailing semiarid conditions have given rise to extensive carbonate deposition. The highest values are recorded in front of discharges wastewaters discharges points and in the south part of the lagoon due to the current direction and the effect of terrigenous detrital inputs (Harbridge et al, 1976;El Arrim, 1996;Essonni, 1998;Oueslati et al, 2018).…”