Assessment of sediment quality in the Mediterranean Sea–Boughrara lagoon exchange areas (southeastern Tunisia): GIS approach-based chemometric methods

Abstract

Concentrations of selected heavy metals (Cd, Pb, Zn, Cu, Mn, and Fe) in surface sediments from 66 sites in both northern and eastern Mediterranean Sea-Boughrara lagoon exchange areas (southeastern Tunisia) were studied in order to understand current metal contamination due to the urbanization and economic development of nearby several coastal regions of the Gulf of Gabès. Multiple approaches were applied for the sediment quality assessment. These approaches were based on GIS coupled with chemometric methods (enrichment factors, geoaccumulation index, principal component analysis, and cluster analysis). Enrichment factors and principal component analysis revealed two distinct groups of metals. The first group corresponded to Fe and Mn derived from natural sources, and the second group contained Cd, Pb, Zn, and Cu originated from man-made sources. For these latter metals, cluster analysis showed two distinct distributions in the selected areas. They were attributed to temporal and spatial variations of contaminant sources input. The geoaccumulation index (I (geo)) values explained that only Cd, Pb, and Cu can be considered as moderate to extreme pollutants in the studied sediments.

Bioaccumulation of trace metals in Hexaplex trunculus: spatial and temporal trends from 2004 to 2011 along the Tunisian coast

“…In the southern localities in the Gulf of Gabès (SF, GA, ZA, and BG), Cd concentrations were the highest among the studied sites. In this area, the major factor behind this metallic pollution is phosphogypsum wastes as showed in several previous works (e.g., Darmoul 1988Darmoul , 1980Darmoul and Vitiello 1980;Kharroubi et al 2012;Ayadi et al 2015;El Zrelli et al 2015). Indeed, high amounts of phosphogypsum are discharged by the phosphate industry in the Gulf of Gabès, being quantified as 11,250 t per day and stretching over big surfaces in the open sea with deleterious effects on biota (Darmoul and Vitiello 1980;Darmoul 1988;Béjaoui et al 2004;Rabaoui et al 2015).…”

“…In GA, this increase can be explained by the continuous rejection of phosphate industrial wastes directly into the marine environment around the city of Gabès, although many interruptions in the production of the factory occurred during the strikes in 2011. However, in the ZA and BG stations, Cd contamination is probably related to the local hydrodynamics that play a key role in the transport of phosphogypsum from the Gabès chemical pole to the southern locations, reaching the Boughrara lagoon (Kharroubi et al 2012). Taking into account the Cd concentrations recorded in the present study (0.1-19.2 μg/g in whole body and 0.2-31.3 μg/g dw in the coiled portion), as compared to previous investigations with this species in Tunisia, the concentration range in the Gulf of Gabès is similar to that reported by Chouba et al (2008) for the period 2003-2004 (20-25 μg/g dw in the foot and 20-40 μg/g dw in the viscera) and lower than those reported by Gharbi-Bouraoui et al (2008) in the Bizerte lagoon (10.6-18.5 μg/g dw in the viscera).…”

“…Many studies were carried out on trace metal contamination in Tunisian coasts, both in sediments of many locations such as the Bizerte lagoon, the Gulf of Tunis, Sfax, Gabès, and Boughrara (Yoshida et al 2002;Ben Garali et al 2010;Ennouri et al 2010;Ghannem et al 2014;Kharroubi et al 2012;Ayadi et al 2015) and biota such as crabs, fishes, bivalves, and gastropods (Hamza-Chaffai et al 1996;Chouba et al 2007;Ennouri et al 2008;Machreki-Ajmi and HamzaChaffai 2008;Mensi et al 2008;Ladhar-Chaabouni et al 2009;Ben Khedher et al 2014;Lahbib et al 2013;KessabiK et al 2014;Rabaoui et al 2014Rabaoui et al , 2015. Most of these works dealt with Cd, Cu, Pb, and Zn, whereas studies focusing on As, Cr, Ni, and Al are still scarce.…”

Spatial Distribution and Source Identification of Heavy Metals in Surface Waters of Three Coastal Areas of Tunisia

“…In the southern region of the Gulf of Gabes, Cd concentrations were highest among the studied sites. In this area, the major factor behind this metallic pollution by heavy metals is phosphogypsum wastes, as shown in several previous works [61,[64][65][66][67]. Indeed, high amounts of phosphogypsum are discharged by the phosphate industry in the Gulf of Gabes, quantified at 11,250 tons per day and stretching along large surfaces in the open sea with deleterious effects on biota [60,[64][65]68].…”

“…These discharges contain various metals, including Cd (39.8 mg kg ), and others like Hg, Mo, Co, and F [69]. According to Kharroubi et al (2012) [66], the amounts of metals found in the flux of the principal effluents from the industrial pole of Gabes are estimated at 300 kg day 1 for Cd, 200 for Cu, 3,500 for Zn, 50 for Pb, 250 for Mn, and 9,330 for Fe.…”