Spatial variability of heavy metals in the coastal area of Monastir and origin of pollution

The Monastir Bay is a semi-enclosed lagoon in the southern Mediterranean. Several degradation characterizes this shoreline. Some punctual studies have shown that pollutants discharged were at the origin of environmental problems. However, the chronological evolution of pollution remained unclear. Thus, a long-term diagnosis (2003–2015) of the evolution of the lead (Pb), Zinc (Zn), Cadmium (Cd), Manganese (Mn), Copper (Cu), and iron (Fe) concentrations, level contamination, distributions, and possible source(s) of Monastir Bay will be able to organize the management of this part to ensure a minimum of its sustainable development. Based on the average concentrations of metals in surface sediments, the pollutant order was Fe > Mn > Zn > Cu > Pb > Cd in 2003 and 2005. Whereas in 2015, it was Fe > Mn > Zn > Pb > Cu > Cd. The enrichment factor showed that northern sector was the most polluted. The 2003 pollution level decreased in 2005 and increased in 2015 where Cd caused highest risk. A significant difference of Cu, Zn, Cd, Mn, and Fe concentrations of north and south sector in 2003 and 2005. But, no significant difference was in 2015. Hence, these pollutants brought by streams, drain, and the harbor depended on pollution level of their sources. The pollutants were redistributed in the north sector by the longshore drift N-S and from the coast to the large by the rip-current. However, in the southern sector because of the barrier (Dahr) and Ras Dimas spit, the pollutants almost stood in place.