Economic losses related to the reduction of Posidonia ecosystem services in the Gulf of Gabes (Southern Mediterranean Sea).

In the early XXth century, the Gulf of Gabes in SE Tunisia used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean basin and was a highly productive hotspot of benthic species. Since the 70's, >500 million t of wet toxic phosphogypsum discharges from a fertilizer industrial complex have led to the gradual loss of ∼90 % of its initial surface. This drastic shrinkage is accompanied by significant value losses originated from the direct and indirect-use services of which the most important ones are small scale fisheries and carbon storage function. Using market valuations of a number of services we estimate economic losses at 105 million € in 2014 (∼915€/ha), i.e., around 115 % of the added value of the gabesian fertilizer factories for the same year. Value losses should increase in the near future in relation with the COP26 agreements which boosted the open carbon credit market. Without actions to reduce negative production externalities caused by the fertilizer industry in the Gulf of Gabes it would not be possible to recover Posidonia ecosystems in this region leading to further economic, ecologic, and cultural losses.

PET plastics as a Trojan horse for radionuclides.

Mismanaged plastic waste interacts with secondary environmental pollutants, potentially aggravating their impact on ecosystems and human health. Here we characterized the natural and artificial radionuclides in polyethylene terephthalate (PET) bottles collected from the industrial littoral discharge of a phosphate fertilizer plant. The activity concentrations in littered bottles ranged from 0.47 (208Tl) to 12.70 Bq·kg-1 (226Ra), with a mean value of 5.30 Bq·kg-1. All the human health risk assessment indices (annual intake, annual effective dose, and excess lifetime cancer risk) estimated for radionuclides associated with ingestion and inhalation of microplastics were below international safety limits. Our results demonstrated that PET can be loaded with natural and artificial radionuclides, and potentially act as a carrier to transfer radionuclides to humans, posing a new potential health risk. Increased use, mismanagement and fragmentation of plastic waste, and continued interaction of plastic waste with radioelements may lead to enhanced radiation exposure in the future.

Rare earth elements characterization associated to the phosphate fertilizer plants of Gabes (Tunisia, Central Mediterranean Sea): Geochemical properties and behavior, related economic losses, and potential hazards.

This is the first study on the behavior and industrial fluxes of rare earth elements (REE) in the coastal fertilizer plants of Gabes (south-eastern Tunisia), the economic losses related to their wastes, and their environmental and human health hazards. The concentrations of 16 REE were assessed in phosphate rock (PR), phosphogypsum (PG) and phosphogypsum foam (PGF) samples, collected from Gabes plants. REE concentrations ranged from 0.23 (for Sc in PG) to 309.33 mg kg-1 (for Ce in PGF). Ce was the most abundant in the three matrices, with concentrations ranging between 80.40 (in PG) and 309.33 mg kg-1 (in PGF). PGF was the most enriched with REE (1075.32 mg kg-1). The annual flow of REE from the fertilizer factories to the marine environment may reach 1523.67 t. The economic losses related to the discharge of phosphogypsum REE in the Gulf of Gabes (GG) was estimated at ~58 million US$ y-1. The potential hazards of discharged REE on the local environment and human health were also evaluated and discussed. These findings show the need for the development of a new industry exploiting REE from phosphogypsum wastes (short term) and phosphate ores (long term) which should lead to reduce its high environmental and human health footprint and to potential economic gains.

Surface sediment enrichment with trace metals in a heavily human-impacted lagoon (Bizerte Lagoon, Southern Mediterranean Sea): Spatial distribution, ecological risk assessment, and implications for environmental protection.

Although several studies previously assessed the contents of trace metals in the sediments of the heavily human-impacted lagoon of Bizerte (northern Tunisia), multi-analytical approaches have not been, so far, used to assess the ecological risks in this water body. This study attempts to provide a comprehensive ecological risk assessment related to the enrichment of the lagoon sediments with seven metals (As, Cd, Cr, Cu, Hg, Pb, and Zn). Significant spatial variations were found in the metal concentrations in sediments, in relation to the degree of coastal human activities and hydrodynamics. This was confirmed with the results of the three pollution indices, Cf, PLI, and Igeo. Concordant results were found with most of the indices used to assess the ecological risks (PERI, PEL, ERL, ERM, M-ERM-Q, TU), indicating higher risks in the southern part of the lagoon. These findings can help to improve the environmental management plan of the socio-economic important lagoon of Bizerte.

Economic impact of human-induced shrinkage of Posidonia oceanica meadows on coastal fisheries in the Gabes Gulf (Tunisia, Southern Mediterranean Sea).

In early XXth century, the Gulf of Gabes (SE Tunisia) used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean Sea, and a highly productive hotspot of benthic/demersal biodiversity. Sponge harvesting and seabed trawling provoked a first step of seagrass degradation. Subsequently, phosphogypsum releases from Gabes Industrial Complex, since mid-1970s, accelerated the decline of the remaining patches. A sharp reduction of coastal fisheries landings took place with the establishment of the last industrial plant units in 1985. The decrease in coastal commercial species landings was found to be directly correlated with P. oceanica decline. The trophic web system switched from a 'benthic-dominated' to a 'pelagic-dominated' system. The economic loss related to coastal fisheries was estimated at ~60 million € in 2014 and the 1990-2014 cumulated loss exceeded 750 million €. This first economic valuation of the only direct-use consumptive value of the coastal fishing service provided by P. oceanica in Gabes Gulf is a first step towards the assessment of the environmental cost of the negative externalities caused by the local phosphate industry. It may be used as a preliminary decision-making aid to consider alternative industrial solutions.

Natural radioactivity and radiation hazard assessment of industrial wastes from the coastal phosphate treatment plants of Gabes (Tunisia, Southern Mediterranean Sea).

This work is a first contribution to the knowledge of natural radionuclides (226Ra, 238U, 40K, and 232Th) activities in phosphate rock (NORM), phosphogypsum, and phosphogypsum foam (TENORM) from the coastal fertilizer plants of Gabes (Southeastern Tunisia) and the assessment of their radiation hazards on human health and the surrounding environment. In the three studied materials, activities were found to be in the range of 35.4 (40K)-375.1 (226Ra), 10.0 (40K)-220.2 (226Ra), and 79.2 (232Th)-1168.6 Bq kg-1 (226Ra), respectively. Considering the studied radionuclides and materials, the corresponding decreasing activity orders were found to be 226Ra > 238U > 40K > 232Th and PGF > PR > PG, respectively. All human health hazard indices exceeded the worldwide recommended safety limits, which show that the workers in Gabes phosphate fertilizer plants as well as the neighboring human community may potentially be exposed to significant radiation, which may cause several diseases and malformations. It is therefore recommended to avoid and/or reduce the potential fertilizer industry radioactive impact in the area.

Characterization of the role of phosphogypsum foam in the transport of metals and radionuclides in the Southern Mediterranean Sea.

The Gabes Gulf had received huge quantities of phosphogypsum discharged from fertilizer plants. Dumping phosphogypsum in coastal waters leads to the formation of foam layers which can float on the surface and be passively transported to distant areas. This is the first attempt at geochemical and mineralogical characterization of these industrial foams in order to understand their role in the dynamic and behavior of contaminants in marine environment. Chemically, phosphogypsum foams (PGFs) are heavily loaded with radiochemical contaminants. Their mineralogical composition showed a prevalence of synthetic gypsum followed by other secondary minerals including halite, quartz, dolomite, sphalerite-Cd and fluorapatite. PGFs are rich in organic matter (OM), precursor of their formation. Once released in gypseous water, the OM in solution undergoes agglomeration, cementing and flotation steps leading to the formation of floating foams. The foams' OM was found to control the mobility of industrial contaminants contributing then to the marine environment pollution. Consequently, PGFs are the main accumulating, transporting and dispersion agent of phosphogypsum radiochemical contaminants. Thus, PGFs removal has the potential to reduce enormously the dynamics of contaminants transferred from the fertilizer plants to the aquatic environment, reducing thus their impacts on the marine environment and health status in Gabes.

Characterization of phosphate rock and phosphogypsum from Gabes phosphate fertilizer factories (SE Tunisia): high mining potential and implications for environmental protection.

Since the establishment of the coastal industrial complex in Gabes city (Gulf of Gabes, SE Tunisia), hundred million tons of untreated phosphogypsum have been discharged in the open sea causing serious environmental problems. To better understand the dynamic and behavior of phosphate/phosphogypsum contaminants from raw ores to marine environment, a chemical, organic, mineralogical, and morphological characterization of phosphate rock and phosphogypsum was conducted using several sophisticated techniques. The chemical analysis showed that phosphate and phosphogypsum contain high loads of trace elements and that the transfer factors of pollutants varied from 5.83% (U) to 140% (Hg). Estimated annual flows of phosphogypsum contaminants into the marine environment ranged between 0.05 (Re) and 87,249.60 (F) tons. The phosphate rock was found to be formed by carbonate fluorapatite, calcite, dolomite, natural gypsum, quartz, calcite-Mg, apatite, pyrite, fluorite, and sphalerite-Cd and phosphogypsum by synthetic gypsum and sphalerite-Cd. The phosphate was found to be richer in organic compounds compared to phosphogypsum. Based on this work, the Tunisian phosphogypsum has a high mining potential and encourages the development of an economically beneficial and environmentally friendly phosphogypsum-treating industry.

Seawater quality assessment and identification of pollution sources along the central coastal area of Gabes Gulf (SE Tunisia): Evidence of industrial impact and implications for marine environment protection.

Temperature, pH and trace elements (F, P, Cr, Cu, Zn, Cd, and Pb) contents were determined in 16 stations as well as in 2 industrial and 2 domestic discharge sources, in the central coastal area of the Gulf of Gabes. Compared to the northern and southern areas of the study area, the highest contents of contaminants were reached in the central area which hosts the coastal industrial complex. The seawater in this central area was also found to be acid and of higher temperature. Based on the Water Pollution Index results, an increasing degradation gradient of the seawater quality was revealed from northern and/or southern stations to central ones, categorized as 'strongly to seriously affected'. Phosphogypsum wastes dumped by the Tunisian Chemical Group (GCT) seem to have continuously degraded the seawater quality in the study area. A rapid intervention is needed to stop the effects on the marine environment.

Biomonitoring of coastal pollution in the Gulf of Gabes (SE, Tunisia): use of Posidonia oceanica seagrass as a bioindicator and its mat as an archive of coastal metallic contamination.

Within the framework of a study on the extent and history of marine pollution in the central area of Gabes Gulf, the concentrations of four trace metals (Cd, Cu, Pb, and Zn) were assessed in three different tissues of the seagrass species, Posidonia oceanica (leaves, rhizomes, and roots), in the mat of P. oceanica meadows at different depths from the sea floor (- 30 to - 150 cm) and in sediments. The results showed that P. oceanica leaves accumulate more Cd, Cu, and Zn, whereas Pb was found to be more concentrated in roots. The analysis of P. oceanica mat highlighted a clear decreasing gradient of trace metal concentrations from lower (- 30 cm) to higher (- 150 cm) depths. Considering that P. oceanica mat continuously rises above the initial level, with a rate of 1 m per century (~1 cm year-1; Molinier and Picard Ann Inst Océanogr Fr 27:157-234, 1952), the latter observation suggested that the pollution level in Gabes Gulf increased continuously during the last few decades. The results of the P. oceanica mapping in the study area showed a continuous regression of its meadows as well as its local disappearance from various areas in the central part of Gabes Gulf. The current status of P. oceanica is most likely due to the cumulative effects of the discharges from the coastal industrial complex of Gabes-Ghannouche represented mainly by the phosphogypsum discharges. This study confirms the usefulness of P. oceanica not only as a bioindicator of the "health status" of coastal ecosystems but also as a record register tracing back the history and temporal evolution of coastal contamination level.

Metal concentration and bioaccessibility in different particle sizes of dust and aerosols to refine metal exposure assessment.

Refined exposure assessments were realized for children, 7-9yrs, in the mining/smelting city of Oruro, Bolivia. Aerosols (PM>2.5, PM1-2.5, PM0.4-1 and PM0.5) and dust (separated in different particle size fractions: 2000-200µm, 200-50µm, 50-20µm, 20-2µm and <2µm) were sampled on football fields highly frequented by children in both the mining and smelting areas. Trace element concentrations (Ag, As, Cd, Cu, Pb, Sb, Sn and Zn) in each size fraction of dust and aerosols, lung bioaccessibility of metals in aerosols, and gastric bioaccessibility of metals in dust were measured. Exposure was assessed considering actual external exposure (i.e. exposure pathways: metals inhaled and ingested) and simulated internal exposure (i.e., complex estimation using gastric and lung bioaccessibility, deposition and clearance of particles in lungs). Significant differences between external and simulated internal exposure were attributed to dissemblances in gastric and lung bioaccessibilities, as well as metal distribution within particle size range, revealing the importance of both parameters in exposure assessment.

Heavy metal contamination and ecological risk assessment in the surface sediments of the coastal area surrounding the industrial complex of Gabes city, Gulf of Gabes, SE Tunisia.

In the present study, the concentrations of 6 trace metals (Hg, Cd, Cu, Pb, Cr and Zn) were assessed in the surface sediments of the central coastal area of Gabes Gulf to determine their contamination status, source, spatial distribution and ecological risks. The ranking of metal contents was found to be Zn>Cd>Cr>Pb>Cu>Hg. Correlation analysis indicated that Cd and Zn derived mainly from the Tunisian Chemical Group phosphogypsum. The other pollutants may originate from other industrial wastes. Metallic contamination was detected in the south of chemical complex, especially in the inter-harbor zone, where the ecological risk of surface sediments is the highest, implying potential negative impacts of industrial pollutants. The spatial distribution of pollutants seems to be due to the effect of harbor installations and coastal currents. The metallic pollution status of surface sediments of Gabes Gulf is obvious, very worrying and requires rapid intervention.