Abstract
Surficial sediments from 18 sites throughout Moknine sebkha, one of the largest urbanized sebkha in the sahel of tunisia, were analyzed for biomarkers ( n-alkanes, hopanes and steranes ) to track the origin of organic inputs. A distinct spatial distribution of aliphatic hydrocarbons in sediments was observed in Moknine sebkha which subdivide this environment in two area . The submerged area is characterized by high concentration of OC 1-4.9%, EOM 2%-49% CO, aliphatic hydrocarbons 1350 µg.kg-1to 3700 µg.kg-1sediment dry weight. Emerged area is characterized by low concentration (OC<1%, EOM<12%OC and F1<1200 µg.kg-1sediment dry weight. Several ratios (e.g. CPI, ACL, NAR, TAR, Pr/Ph…) were used to evaluate the possible sources of terrestrial-lacustrine inputs of these hydrocarbons in the sediments. The various origins of aliphatic hydrocarbons were generally biogenic, including both terrigenous and cyanobacteria. The source of contamination is not petroleum. , the predominance of biogenic in combination with petrogenic hydrocarbons was indicated by the biomarkers. αβ trishomohopane C33 indicate an anthropogenic contribution (wastewater) in two stations (treated domestic wastewater (ssm1-2) and untreate industrial wastewater ssm6). The presence of biogenic hopanes (17β(H), 21β(H)-hopanes) indicate the biogenic origin of organic matter in the Moknine sebkha. The UCM not indicate petrogenic origin but high activities of bacteria in highly saline system.
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