Sediments distribution of trace metals in a coastal lagoon (Southern Sardinia, Mediterranean Sea): assessment of contamination and ecological risk

Coastal lagoons are subject to several sources of contaminations. To shade light on the contamination level of the Santa Gilla lagoon (Tyrrhenian Sea) we investigated the spatial distribution of Cr, Ni, Pb, Zn and Hg in sediments and their correlation with grain size and organic matter contents. Moreover, sediment contamination levels and the ecological risk associated with metal concentration were assessed using different abiotic indicators. The lagoon is characterised by low levels of contamination, with exceptions for Pb and Hg, whose distribution reflects the position of an old chlor-alkali plant and that of an airport. These results indicate that the restoration put in place 30 years ago have not reached the expected target and that the presence of the airport deserves further attention. In the outer section of the lagoon, where clam fishery occurs, we observed low levels of contamination suggesting that such artisanal fishery could somehow help mobilising metals. We conclude that the area exposed to Hg pollution, though tentatively restored, still suffers of a potential risk of ecosystem deterioration. We pinpoint that further investigations on the mobility, bioavailability and toxicity of metals are needed to finally address the actual impairment of the Santa Gilla lagoon.

沿海潟湖面临多种污染来源。为阐明第勒尼安海（Tyrrhenian Sea）圣吉拉潟湖的污染水平，本研究调查了沉积物中铬（Cr）、镍（Ni）、铅（Pb）、锌（Zn）与汞（Hg）的空间分布特征，及其与沉积物粒度和有机质含量的相关性。此外，本研究采用多种非生物指标，评估了该潟湖的沉积物污染水平及与金属浓度相关的生态风险。该潟湖整体污染水平较低，但铅（Pb）与汞（Hg）除外，二者的空间分布分别与一处老旧氯碱厂（chlor-alkali plant）和一座机场的位置相吻合。研究结果表明，30年前实施的修复工程未达到预期目标，该机场周边区域仍需进一步关注。在潟湖外侧开展蛤类捕捞的区域，我们观测到较低的污染水平，这表明此类手工捕捞活动或可在一定程度上促进金属的活化迁移。综上，尽管已尝试性开展修复，受汞（Hg）污染的区域仍存在生态系统退化的潜在风险。本研究明确指出，需进一步开展关于金属迁移性、生物可利用性与毒性的研究，以最终明确圣吉拉潟湖的实际生态受损状况。