Determination of metals in species of commercial interest from marine wetlands, coastal and offshore areas influenced by Po River outflows

The impact of heavy metal pollution on estuaries and coastal environments is a matter of major concern worldwide because of their persistency and tendency to bioaccumulate in the aquatic ecosystems, in addition to their toxicity [1]. These elements can derive from natural sources, influenced by bedrock geology of the drainage catchment and by weathering. However, along the Italian Northern Adriatic coast, anthropogenic pressure, in particular agriculture, industrial and municipal discharges, significantly increased the naturally occurring amounts of metals in the aquatic environment [2]. At the same time, Po delta and neighboring areas are traditionally exploited for fishery and mollusks farming, providing many species commonly used in Italian diet. In this context, the aim of this study is to evaluate the concentration of several metals (Hg, As, Cd, V, Cr, Mn, Fe, Ni, Cu, Zn, Ba, Pb) in five marine species of commercial interest collected in different environments influenced by Po River outflow. Farmed mollusks come from both wetland (Tapes philippinarum) and coastal areas (Chamelea gallina), while native mussels (Mytilus galloprovincialis) and fish species (Solea solea and Squalus acanthias) were caught offshore. All species were sampled twice between 2018 and 2019. Furthermore, the metal content was measured also in surface sediments, to assess the environmental contamination of farming and capture areas. The analytical determination was carried out by different atomic spectroscopy techniques, which were selected based on their analytical figure of merit. In detail, graphite furnace atomic absorption, cold vapor atomic absorption spectrometry (mercury analyzer), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectrometry (ICP-MS) were employed. Certified Reference Materials (CRMs) were employed for quality control purposes. The results highlighted a correlation between the environmental state of the sites and metals content in the selected samples. The metals distribution in sediments were compared with the lithogenic composition, to attempt to discriminate between natural and anthropic input sources. In addition, the concentrations found in the selected marine species were correlated with those in surface sediments, thus confirming the tendency to bioaccumulate of heavy metals. Finally, contamination levels of hazardous metals in sediments and biota were compared with Environmental Quality Standard (EQS) and threshold levels (TL) for human health.