Marco Schintu

Santa Gilla lagoon (Italy): a mercury sediment pollution case study. Contamination assessment and restoration of the site

Abstract The Santa Gilla lagoon, on the southern coast of the island of Sardinia (Italy), has received industrial discharge of mercury, lead and zinc compounds, as well as municipal untreated sewage for several decades from the urban area of Cagliari (about 400 000 inhabitants). The lagoon, which covers an area of 15 km 2 of shallow waters, has always represented an important source of quality fish and shellfish for the island. Pollution sources were brought under control only in the mid-1980s, when a costly restoration program, which is still in progress, was started. About 26 tons of mercury, discharged from a chlor-alkali plant, have been estimated to have been deposited in the lagoon since the mid-1960s, mostly confined in an area of about 2 km 2 in front of the industrial area. According to the restoration project this area has been isolated with proper dykes and used to discharge sediments dredged from the most polluted sectors of the lagoon. It was finally covered up with sediments dredged from cleaner areas of the lagoon with the aim of using it for aquaculture. This work reviews several investigations carried out on the sediments of the S. Gilla lagoon to monitor and control the real extent and hazard of the mercury pollution. Recent data on the mercury concentration in the sediments of the lagoon after remediation were compared with previous data on the same area and the effectiveness of the clean-up plan was evaluated.

Macroalgae and DGT as indicators of available trace metals in marine coastal waters near a lead-zinc smelter.

The levels of Cd, Cu, Pb, and Zn were determined in the commonest species of green, red, and brown algae collected from five coastal sites in south-western Sardinia (Italy), an area with a long history of mining and smelting. The usefulness of employing Enteromorpha sp. and Padina pavonica (L.) Thivy to monitor metal pollution was evaluated, while diffusive gradients in thin films (DGT) devices were used to measure dissolved metals in seawater. Levels of Cd and Pb were high enough to be of environmental concern in the whole study area. A significant relationship was found between the content of Pb in P. pavonica and DGT-labile Pb in seawater, suggesting that gross elemental concentrations of nonessential metals such as Pb in algal tissues are apparently controlled by the abundance of dissolved metal species in the ambient seawater. The results pointed out the usefulness of using both DGT and algal methods for a better understanding of trace metal availability in coastal waters.

Sedimentary records of heavy metals in the industrial harbour of Portovesme, Sardinia (Italy)

Abstract The anthropogenic fluxes of Hg, Cd, Pb and Zn were determined in four sediment cores collected in the harbour of Portovesme, Italy, facing an industrial area containing a lead–zinc smelter, an aluminium production plant and a coal-fired power generation plant. The analytical results and the radiodating of sediment cores show extremely high concentrations of Hg and Cd in the sediments that can be ascribed mostly to the discharge of the liquid effluent from the smelter since the late 1960s. Based on the different extractability of metal species, the anthropic origin of metal pollution as well as the risk of remobilisation of the metals into the marine environment is highlighted.

Interpretation of coastal sediment quality based on trace metal and PAH analysis, benthic foraminifera, and toxicity tests (Sardinia, Western Mediterranean)

An integrated approach for the assessment of coastal sediment quality was utilised in three areas of Sardinia (Western Mediterranean, Italy). Sediments were analysed for trace metals and polycyclic aromatic hydrocarbons (PAHs), while benthic foraminifera were used as bioindicators. Furthermore, the embryo-toxicity test was used to provide ecologically relevant information using rapid and cost-effective screening tools. The aim was to evaluate the usefulness of coupling different analytical tools. The results revealed the presence of polluted sediments in areas exposed to petrochemical industries, smelters or military settlements. However, while foraminifera have presented similar indications for chemical analysis of contamination levels in the different areas, the toxicity test exhibited a poor relationship with the contaminants measured individually. The results raise questions concerning the bioavailability of contaminants released by sediments in the water column. Overall, the toxicity rate was significant in many samples in comparison with other sites studied in other Mediterranean regions.

Using SPMDs to monitor the seawater concentrations of PAHs and PCBs in marine protected areas (Western Mediterranean)

Aqueous concentrations of individual polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in coastal sites of two marine protected areas (MPAs), that is, Asinara and the La Maddalena Archipelago, in Sardinia (Western Mediterranean Sea). The use of semi-permeable membrane devices (SPMDs) enabled the detection of dissolved PAHs and PCBs, even in very low concentrations of (pgL(-1)), in seawater. The results reveal significant differences between the two sampling areas relative to the concentration of the individual PAHs, which provide information concerning the pollution sources affecting relatively pristine environments. The PCBs were generally observed at levels below the detection limits of the utilised method.

Heavy metal distribution and mobilization in sediments from a drinking water reservoir near a mining area

This study was prompted by concern about the possible heavy metal contamination of the Flumendosa lake, a drinking water reservoir located downstream from the Funtana Raminosa mining area, in Sardinia (Italy). Extremely high concentrations of Pb, Cd and Cu were found in the Rio Sarraxinus, a small tributary of the Flumendosa river which drains the mining area. Sediment cores from the reservoir showed high contents of all three metals. In order to investigate the partitioning of the metals in the main components of the sediments, a scheme of sequential extractions was used. The results indicate an important role of the organic matter in binding Pb and Cd in the sediment of the reservoir. Percentages of non-residual Pb and Cd bound to the organic matter were significantly higher in the reservoir sediments than in those from the tributaries, while the highest percentages of Cu were associated with the organic matter both in lake and in river sediments. However most of the Cd and Pb both in lake and fluvial sediments were bound to the carbonates and to Fe-Mn oxides, which are exposed to chemical changes and then susceptible to metal remobilization in the water.

Organomercury determination in biological reference materials: Application to a study on mercury speciation in marine mammals off the Faröe Islands

The potential use of graphite furnace atomic absorption spectrometry (GF-AAS) for the organic mercury determination in marine biological tissues was evaluated. Following its isolation by acid extraction in toluene, organic mercury was recovered in aqueous thiosulfate and measured by GF-AAS. The detection limit was 0.01 microgram Hg/g (as methyl mercury). Analyses were conducted on three reference standard materials certified for their methyl mercury content, DOLT-1, DORM-1, and TORT-1, provided by the National Research Council of Canada. The method resulted in very good recovery and reproducibility, indicating that GF-AAS can provide results comparable to those obtained by using more expensive and time consuming analytical techniques. The method was applied to the analysis of liver tissues of pilot whale specimens (Globicephala melas) from the drive fishery of the Faröe Islands (northeast Atlantic). The results provided useful information on the proportion of different mercury forms in the liver of these marine mammals.

Inorganic and methyl mercury in inland waters

Abstract The proportion of methylmercury to the amount of total mercury has been determined in river and lake water samples from the Ottawa Valley in Canada. The results showed that a relatively constant equilibrium between organic and inorganic mercury has been maintained over the last decade in the Ottawa area. A simple method to determine both organic and inorganic mercury in natural waters is described. After the extraction with dithizone-chloroform, inorganic mercury was back extracted to aqueous solution with sodium nitrite, while methylmercury was recovered to the aqueous medium with sodium thiosulfate. Mercury was determined by a two-stage gold amalgamation technique in conjunction with cold vapour atomic absorption spectrometry. Preconcentrating the mercury from 21. samples, the method provided a detection limit of 0.1 ng/l.

Heavy metal accumulation in surface sediments at the port of Cagliari (Sardinia, western Mediterranean): Environmental assessment using sequential extractions and benthic foraminifera

Superficial sediments were taken at the port of Cagliari (Sardinia, Italy), which includes the oil terminal of one of the largest oil refineries in the Mediterranean. Significant trace metal concentrations were found in the whole port area. Sequential extraction of metals from the different sediment fractions (BCR method) showed a higher risk of remobilisation for Cd, which is mostly bound to the exchangeable fraction. Foraminiferal density and richness of species were variable across the study area. The living assemblages were characterized by low diversity in samples collected close to the port areas. Ammonia tepida and bolivinids, which were positively correlated with concentrations of heavy metals and organic matter content, appeared to show tolerance to the environmental disturbance. The sampling sites characterized by the highest values of biotic indices were located far from the port areas and present an epiphytic and epifaunal biocoenosis.

An ecotoxicological approach for the Boka Kotorska Bay (south-eastern Adriatic Sea): First evaluation of lysosomal responses and metallothionein induction in mussels

Mytilus galloprovincialis was used as a biomonitoring organism in Boka Kotorska Bay, a coastal transitional ecosystem in south-western Montenegro. Native mussels were collected in June 2008 at four sites thought to be differently impacted. Biological effects were investigated analysing both generic and specific biomarkers at cellular level (metallothionein content, lysosomal membrane stability, lipofuscin and neutral lipid accumulation, lysosomal structural changes). Trace element levels in mussels were quite low, only Cu and Zn exhibiting slight increases in the two sampling sites of Tivat Bay, the first one in front of a small working dockyard and the other in the water area of a former Naval dockyard. Mussels collected from these sites exhibited the highest values in neutral lipid and lysosomal volume density and the lowest neutral red retention times. Metallothionein content was always low, reflecting the minor body burden of the trace elements and suggesting a non-relevant environmental induction.