Natural vs anthropogenic components in sediments from the Po River delta coastal lagoons (NE Italy)

Scallop shells as biosorbents for water remediation from heavy metals: Contributions and mechanism of shell components in the adsorption of cadmium from aqueous matrix

To ascertain their potential for heavy metal pollution remedy, we studied the adsorption mechanism of cadmium onto scallop shells and the interactions between the heavy metal and the shell matrix. Intact shells were used to investigate the uptake and diffusion of the metal contaminant onto the shell carbonatic layers, as well as to evaluate the distribution of major and trace elements in the matrix. LA-ICPMS measurements demonstrate that Cd is adsorbed on a very thin layer on the inner and outer surfaces of the shell. Structural and thermal analyses showed the presence of 9 wt.-% of a CdCO3 phase indicating that the adsorption is mainly a superficial process which involves different processes, including ion exchange of Ca by Cd. In addition, organic components of the shell could contribute to adsorption as highlighted by different metal uptake observed for shells with different colours. In particular, darker shells appeared to adsorb more contaminant than the white ones. The contribution of the organic shell components on the adsorption of heavy metals was also highlighted by the element bulk content which showed higher concentrations of different metals in the darker specimen. Raman spectroscopy allowed to identify the pigments as carotenoids, confirmed by XRD measurements which highlighted the presence of astaxanthin phases. The results presented here provide new insights into the Cd adsorption mechanism highlighting the important contribution given by the organic components present in the biogenic carbonate matrix. Furthermore, the high efficiency of Cd removal from water by scallop shells, supported by adsorption kinetic and isotherm studies, has been demonstrated.

Current trends and challenges in the analysis of marine environmental contaminants by isotope ratio mass spectrometry

An increasing number of organic and inorganic pollutants are being detected in the marine environment, posing a severe threat to the ecosystem and human health, even in trace concentrations. Isotope ratio mass spectrometry (IRMS) is one of the critical methods for determining the origin and fate of environmental pollutants and characterising their transformation processes. It has been used for a relatively long time for ecological monitoring of some well-studied industrial hydrocarbons at contaminated sites. However, the method still faces many analytical challenges. This review provides a comprehensive overview of recent technical advances concerning IRMS analysis of various contaminants and discusses typical pitfalls encountered in marine environment analysis. Particular attention is given to the study of sampling techniques and sample preparation for examination, often the keys to successful research given the complexity of marine matrices and the diverse and numerous nature of contaminants. Prospects for developing IRMS to monitor pollution sources and pollutant transformation in the marine environment are outlined.

Multiproxy characterization of sedimentary facies in a submarine sulphide mine tailings dumping site and their environmental significance: The study case of Portmán Bay (SE Spain)

Mining activities are essential to our society, but ore extraction and treatment produce waste that must be stored in safe places without harm to the environment. For a long time, seafloor disposal has been viewed as a cheap option with barely visible impacts. In Portmán Bay, SE of Spain, large amounts of tailings from open pit sulphide mining were discharged directly into the coastal sea over 33 years, thus forming a massive deposit that completely infilled the bay and expanded seawards over the inner continental shelf. Here we present the first multiproxy physicochemical characterization of the submarine tailings in Portmán Bay, mostly by using non-destructive techniques, also including pre-dumping and post-dumping sediments. Eight distinct sedimentary facies, grouped in four stratigraphic units, have been thus identified in a set of up to 4.3 m long gravity cores totalling more than 60 m. Geogenic and anthropogenic geochemical proxies consistently allow differentiating pre-dumping sediments from tailings. Potentially toxic metals if made bioavailable can reach high concentrations in units including or formed exclusively by tailings (i.e. up to 3455, 2755 and 1007 mg kg^-1 for Pb, As, and Zn, respectively). Some physical properties, such as magnetic susceptibility, are particularly useful as the tailings are rich in Fe-bearing minerals (>30% Fe in some layers). Estimated sedimentation rates show a strong gradient from proximal to distal locations, with rates in excess of 50 cm yr^-1 to less than 1 cm yr^-1. We ultimately document the history of the transformation of Portmán Bay from an almost natural state to a new condition after a long period of massive dumping of mine tailings. Our study provides guidance to further assessments in a context where the diversity of marine environments impacted by the disposal of mine waste is expected to grow in the near future.

Traceability and Authentication of Manila Clams from North-Western Adriatic Lagoons Using C and N Stable Isotope Analysis

In the Adriatic lagoons of northern Italy, manila clam (Ruditapes philippinarum) farming provides important socio-economic returns and local clams should be registered with the Protected Designations of Origin scheme. Therefore, there is a need for the development of rapid, cost-effective tests to guarantee the origin of the product and to prevent potential fraud. In this work, an elemental analysis (EA) coupled with isotope ratio mass spectrometry (IRMS) was employed to identify the isotopic fingerprints of clams directly collected onsite in three Adriatic lagoons and bought at a local supermarket, where they exhibited certification. In particular, a multivariate analysis of C/N, δ¹³C and δ¹⁵N in manila clam tissues as well as δ¹³C in shells and Δ¹³C (calculated as δ¹³C_shell–δ¹³C_tissues) seems a promising approach for tracking the geographical origin of manila clams at the regional scale.

Sources and Metal Pollution of Sediments from a Coastal Area of the Central Western Adriatic Sea (Southern Marche Region, Italy)

Sediments represent a critical compartment of marine coastal ecosystems due to the toxic and long-lasting effects of the contaminants buried therein. Here, we investigated the properties of surficial sediments in front of the Southern Marche Region coast (Central Adriatic Sea, Italy). The grain size of the surficial sediments was determined by X-ray sedigraphy. TN and OC contents were determined by elemental analysis. The concentrations of Al, Fe, Mg, K, S, Ca, Ti, P, Na, Mn, Mg, Li, As, Ba, Ga, Pb, Sr, and Zn were determined by ICP-OES to evaluate their spatial patterns and temporal trends. A Q-mode Factor Analyses was applied and resulted in the identification of three compositional facies (Padanic, Coastal, and Residual) characterized by common biogeochemical, mineralogical, sedimentological properties, transport pathway, and source. Some pollution indicators, such as the enrichment factor, the geoaccumulation index, and the pollution load index were calculated to assess the deviation from the natural background levels. The results showed a pollution by As and Ba due to the human activities in the 20th century. Furthermore, a general decreasing of Al, Ti, P, Co, Cr, Cu, Ga, Ni, Pb, Sc, V, and Y concentrations from the background levels suggested a change in the sedimentation processes during the last decades.

Functional Feeding Groups of Aquatic Insects Influence Trace Element Accumulation: Findings for Filterers, Scrapers and Predators from the Po Basin

For this study, we measured the concentrations of 23 trace elements (Al, As, Ba, Bi, Cd, Cr, Co, Cu, Fe, Ga, Hg, In, Li, Mn, Mo, Ni, Pb, Se, Sr, Ti, Tl, V, and Zn) in the whole bodies of three functional feeding groups (FFG) (filterers-Hydropsychidae, scrapers-Heptageniidae, and predators-Odonata) of aquatic insects collected from two sites in the Po basin (Po Settimo and Malone Front, Northwest Italy) to determine: (a) how FFG influence trace element accumulations, (b) if scrapers accumulate higher elements compared to the other FFG, since they graze on periphyton, which represents one of the major sinks of metals, and (c) the potential use of macroinvertebrates to assess the bioavailability of trace elements in freshwater. The hierarchical clustering analysis generated three main groups based on trace element concentrations: the most abundant elements were Fe and Al, followed by Sr, In, Zn, V, Mo, and Cu. Tl was below the limit of detection (LOD) in all FFG. Ga was detected only in scrapers from both sites and Hg only in predators from Po Settimo. The principal component analysis showed that concentrations of Al, As, Bi, Cd, Co, Cr, Ga, Fe, In, Mn, Pb, Ni, and Sr were highest in scrapers, suggesting that trace elements accumulate from the ingestion of epilithic periphyton (biofilm). Odonata (predators) accumulate certain elements (Ba, Hg, Li, Se, V, Ti, and Zn) in higher concentrations by food ingestion composed of different aquatic organisms. Differently, Cu and Mo concentrations were the highest in filterers due to their bioavailability in the water column. Non-metric multidimensional scaling clearly differentiated the FFG based on their ability to accumulate trace elements. The findings from this study represent an important step toward the definition of an innovative approach based on trace element accumulation by macroinvertebrates.

Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Three Gorges Reservoir

In order to understand the spatial distribution and ecological risk of heavy metal pollution in the sediments of the Three Gorges Reservoir, surface sediment samples in six typical tributaries and estuaries were analyzed. The heavy metal content in sediment was detected by ICP-MS (PE Elan DRC Ⅱ, PerkinElmer, Waltham, MA, USA) after digestion by mixed acid. The data were evaluated and analyzed using multiple methods, including the potential ecological risk index, the geoaccumulation index (Igeo), and cluster analysis. The results show that the tributary surface sediments were polluted by heavy metals to a certain extent. Cu, Zn, Pb, and Cr have been enriched in sediments in recent years. The results of Igeo show that the pollution degree is as follows: Pb > Cu > Zn > Cr > Cd > Ni > As > Hg. According to the potential ecological risk index, the grades of Yunyang, Xiaojiang, and Xinjin are all medium risk, and Cd has the highest contribution rate. Combined with field investigation data, cluster analysis, and correlation analysis, we conclude that Cu, Zn, and Cr are likely to come from agricultural chemical fertilizers and industrial sewage, while Pb mainly comes from the discharge of ship fuel.

Evaluation of heavy metals background in the Adriatic Sea sediments of Abruzzo region, Italy

This work focuses on the characterization of background levels of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in seabed marine sediments of the central Adriatic Sea, collected up to 10 km far from the Abruzzo region coastline (Italy). The used approach follows the guidelines established by the Decree of the Italian Ministry of Environment, n. 173/2016, concerning the determination of threshold values of metal concentration, and including only samples with low or absent toxicological content. A statistical analysis, using the adjusted Tuckey's boxplot to identify the percentiles and potential outliers, was performed. The background concentrations were calculated as the values of the 90th percentile of distribution, according to the national regulation. This study represents the first attempt to calculate the background levels of marine sediments done at regional level in Abruzzo. A few outliers have been found, and interpreted as potential anthropic contamination.

Distribution and risk assessment of trace metals in riverine surface sediments in gold mining area

Recognizing the pollution characteristics and potential risks of trace metals in sediments are important to protect water ecosystem safety. In the present study, a systematic investigation was performed to assess the pollution and risk level of trace metals in river sediments located in the greatest gold production base in China. The geo-accumulation index was used to assess the contamination degree. The sediment quality guidelines and potential ecological risk index were employed to complete an ecological risk assessment. A non-carcinogenic health risk assessment was also carried out to evaluate potential adverse health risks. Correlations and principal component analyses were applied to check relationships among trace metals and ascertain potential pollution sources. The results suggested that the sediments in the river were most polluted by As, Cd, and Hg followed by Cu, Pb, and Zn. The assessment of potential human health risk revealed that there was no significant non-carcinogenic risk to the inhabitants. Gold mining and smelting activities and the long-term excessive application of fertilizers and agrochemicals were identified as the main anthropogenic releases. This study contributed an understanding that possible sources, contamination degree, and ecological risk level of trace metals in riverine surface sediments in a gold mining area.