Water quality in a protected natural wetland: El Kelbia sebkhet, Tunisia

Surface waters were collected from a Tunisian protected wetland, sebkhet El Kelbia, to determine their chemical composition and to characterize this ecosystem in terms of water quality. Mineralogical composition of sediments in this sebkhet consists of evaporites, clays, quartz, calcite and oxides. The average total nitrogen concentration was 0.325 μg/g (SD = 0.068), with 0.089 μg/g as nitrate, 0.018 μg/g as nitrite and 0.023 μg/g as ammonia. The total phosphorus concentration was 0.081 μg/g (SD = 0.011) with 0.044 μg/g determined as PO₄ ³⁻. The total dissolved elements not including silica are about 16–248 meq/L and are characterized by relatively high spatial variability in the lake basin. The average concentration of trace elements from the highest to the lowest is as follows: Sr > Fe > Pb > Ba > Cd > Cu > Mn > Cr. The quality of the wetland waters was examined by comparing the concentrations of dissolved trace and major elements with those of Tunisian and European standard values. The comparison revealed that the quality of the current waters of the protected El Kelbia lake is considered to be satisfactory, but there is a need to prevent any threat of contamination that may arise from Pb and Zn from past mining activities and unauthorized dumping.