Spatial patterns and temporal trends of trace metal mass budgets in the western Adriatic sediments (Mediterranean Sea)

Geochemistry of trace metals in surface sediments from the continental slope of the states of Sergipe and Alagoas, Northeastern Brazil

Geochemical analyses were used to determine the origin and identify the main factors that lead to the metal trace distribution on the surface sediments from the continental slope of Sergipe in Brazil. Sediment samples were collected during the dry and rainy periods, from 36 sampling points distributed at water depths from 400 to 3000 m. In general, no effect of seasonality was observed on the metal concentrations and no significant differences were observed between the depth ranges. The correlation analysis indicated the continental origin as the most predominant, followed by authigenic deposition. Anthropogenic enrichment was not noted, nor was the possibility of adverse aquatic biota effects. The results made it possible to understand the contribution of rivers in the transport and transfer of particulate matter to the coastal region, in addition to providing new information on the content of trace metals in tropical Atlantic sediments.

Trace metals and polycyclic aromatic hydrocarbons in the Eastern Mediterranean sediments: Concentration ranges as a tool for quality control of large data collections

Assessing the status of marine pollution at regional and sub-regional scales requires the use of comparable and harmonized data provided by multiple institutions, located in several countries. Standardized data management and quality control are crucial for supporting a coherent evaluation of marine pollution. Taking the Eastern Mediterranean Sea as a case study, we propose an approach to improve the quality control procedures used for sediment pollution data, thus supporting a harmonized environmental assessment. The regional ranges of contaminant concentrations in sediments were identified based on an in-depth literature review, and the lowest measured concentrations were evaluated to determine the "background concentrations" of chemical substances not yet targeted in the Mediterranean Sea. In addition, to verify the suitability of the approach for validating large data collections provided by multiple sources, the determined ranges were used to validate a regional dataset available through EMODnet data infrastructure.

Assessment of potential variability of cadmium and copper trace metals using hindcast estimates

Trace metals are vital to primary productivity and play an essential role as main components in regulating oceanic biogeochemical cycles. Dissolved and particulate trace metals within the water column may vary due to primary production, temperature, and nutrient changes, factors that may also vary spatially and temporally. Furthermore, assessment of trace metals mainly relies on in situ observation, and so wide-area investigation of trace-metal concentration may be challenging and subject to technical constraints. A specific approach is therefore necessary that combines biogeochemical proxies, satellite data, and trace-metal linear correlation. This study aims to assess the potential spatio-temporal variability of sea surface cadmium (Cd) and copper (Cu) concentrations in Indonesian seas and surrounding areas. The correlations of Cd and Cu concentrations with primary production and nutrient data were used to convert hindcast satellite data into estimates of the metals' concentrations. The potential variability of trace metals can be determined by overlaying both data. Indonesia's Fisheries Management Areas (FMAs) were used for data clustering and analysis. The results show that Cd and Cu trace metals have similar distribution patterns throughout the year. However, dissolved Cu has a more diverse coverage area than dissolved Cd, including within the Halmahera, Seram, and Maluku Seas (FMAs 716 and 717), the Makassar Strait (FMA 717), and the Java-Sumatra upwelling area (FMA 573). Both Cd and Cu concentrations in the Java-Sumatra upwelling region follow the periodic upwelling pattern. Overall, both Cd and Cu show a declining trend in concentration from 2012 to 2019. It is estimated that dissolved Cd concentration declined from 1500-2000 pmol/kg in 2012 to 1000-1500 pmol/kg in 2019 for all locations. Dissolved Cu concentration decreased from 30-35 nmol/kg in 2012 to 25-30 nmol/kg in 2019. Estimated dissolved Cd and Cu follow the linear functions of silicate (SiO₄), nitrate (NO₃), and primary productivity. The fluctuation of anthropogenic activities and global warming are likely to indirectly impact the decline in metal concentrations by affecting nutrients and primary productivity.

Vertical profiles of trace elements in a sediment core from the Lambro River (northern Italy): Historical trends and pollutant transport to the Adriatic Sea

River sediments generally act as a sink for trace elements but, when resuspended, they contribute to long-term downstream transport of contamination, which may finally reach the marine environment. This study analyzed these processes in a complex aquatic system that includes a contaminated tributary, the Lambro River (Northern Italy) and its recipient and main Italian watercourse, the Po River, with the prodelta in the Adriatic Sea. The study was conducted from a historical perspective which, covering the last 50 years, examined the main driving events such as the inputs of contaminants, the construction of WWTPs and the evolution of environmental legislation. The time trend of trace element contamination was analyzed in a sediment core collected in the Lambro River and dated 1962-2011. The highest enrichments were found for Hg, Zn, Cu, Pb and Cd, which showed similar trends, with EF maxima in the '60s-'90s (172, 56, 40, 28 and 21, respectively), following industrial and urban development, and a general decreasing pattern after the late '90s. Only in the 2000s the ecological risk associated with metal contamination showed mean PEC Quotients stably below 1. The results of a literature survey on sedimentary trace elements in the Po River and the prodelta for the last 50 years were then compared to the Lambro sediment core. A significant contribution to Cu, Zn, Pb, Hg and Cd contamination was proved to derive from Lambro sediment transport. In the prodelta, increasing Ni and Cr concentrations were also evidenced, likely as a result of enhanced soil erosion in the Po basin. This study highlights the key role of WWTPs, of lower-impact industrial processes and of environmental legislation in reducing contaminant inputs. It also emphasizes the active contribution of riverine sediment-bound contamination to long-distance marine sediment quality.

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.

Natural Versus Anthropic Influence on North Adriatic Coast Detected by Geochemical Analyses

This study focused on the geochemical and sedimentological characterization of recent sediments from two marine sites (S1 and E1) located in the North Adriatic Sea, between the Po River prodelta and the Rimini coast. Major and trace metal concentrations reflect the drainage area of the Po River and its tributaries, considered one of the most polluted areas in Europe. Sediment geochemistry of the two investigated sites denote distinct catchment areas. High values of Cr, Ni, Pb and Zn detected in sediments collected in the Po River prodelta (S1 site) suggest the Po River supply, while lower levels of these elements characterize sediments collected in front of the Rimini coast (E1 site), an indication of Northern Apennines provenance. Historical trends of Pb and Zn reconstructed from the sedimentary record around the E1 site document several changes that can be correlated with the industrialization subsequent to World War II, the implementation of the environmental policy in 1976 and the effects of the Comacchio dumping at the end of 1980. At the S1 site, the down core distributions of trace elements indicate a reduction of contaminants due to the introduction of the Italian Law 319/76 and the implementation of anti-pollution policies on automotive Pb (unleaded fuels) in the second half of the 1980s.

Trace metal variability controlled by hydrodynamic processes in a polluted inner shelf environment (Besòs prodelta, NW Mediterranean)

Trace metal pollution of coastal sediment is monitored in many countries to control its evolution and the effectiveness of preventive and corrective measures. However, temporal variability of trace metal pollution is not always due to changes in pollution management, as natural processes can induce a significant variability in the trace metal content of sediment and particulate matter, especially in strongly polluted coastal areas. To study this variability, time series of trace metals in particulate matter and bottom sediments were recorded along with hydrographic and hydrodynamic parameters in the most highly polluted zone of the Besòs River prodelta. Two benthic tripods equipped with current meters, turbidimeters and sediment traps were deployed at 20 and 30 m water depth from late-September to mid-June and sediment cores were taken four times at each site during the deployment period. Trace metal content in the trapped particulate matter and the surface sediment increased during storm events, which can resuspend and erode several cm of subsurface sediments with higher pollution levels from earlier industrial times. After the storms, significant accumulation of less polluted sediment began, and near-bottom currents redistributed it, decreasing trace metal contents in surface sediments and trapped particulate matter. Therefore, energy conditions previous to monitoring sampling must be considered in order to evaluate the evolution of trace metals in inner shelf polluted sediments.

Sediment Dynamics of the Neretva Channel (Croatia Coast) Inferred by Chemical and Physical Proxies

We examined the transport of sediments and their surficial pathways from the mouth of Neretva River, through the Neretva Channel, toward the Adriatic Sea. This research was based on twelve box-cores and five grab samples collected within the Neretva Channel. Sediment dynamics were evaluated using several proxies, such as organic matter, radiochemical isotopes and select metal concentrations and physical parameters. The data analysis showed that the influence of the river on particle distribution along the Neretva Channel decreases northward, with an estimated sediment accumulation rate ranging from 1.9 to 8.5 mm/yr. The lowest accumulation rate was found in the sector not influenced by river inflow, whereas the preferential sediment accumulation area is in the center of the basin. We speculate that dispersion and accumulation of sediments are both driven by an eddy in the waters of the Neretva Channel triggered/or intensified seasonally by the interaction of karstic springs, river input and Adriatic Sea waters. Our results indicate that the anthropogenic factor does not affect the concentration of metals within the channel and that the river particles dynamics determine the Pb areal distribution, while Cr and Ni have a possible source located to the northwest of the river-mouth.

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.

Combined classification and source apportionment analysis for trace elements in western Philippine Sea sediments

Trace elements have been widely used for classification (of variables and of samples) and source apportionment studies, but the comparison and combination of the two is uncommon in previous works. In this paper, the grouping of trace elements, clustering of samples, and source identification were merged for an integrated understanding of the origin and distribution of trace elements in western Philippine Sea sediments. The grouping and clustering studies were implemented by a nonlinear clustering method called a self-organizing map (SOM), and the source identification was accomplished by a nontraditional factor analysis method called positive matrix factorization (PMF). Through visualization and clustering techniques, the SOM simultaneously classified a database of 26 trace elements into four groups of trace elements and five clusters of samples. Each sample cluster occupies a certain geographic area and is characterized by high concentrations of trace elements that are classified within one or two groups. Five potential sources were identified by PMF, representing the land mass of Taiwan Island, anthropogenic emissions from Taiwan, nutrient exportation from the South China Sea, mineral attachment in the deep ocean, and biogenetic components and riverine inputs from the Luzon Islands. The spatial distributions of the sample clusters are comparable to the ranges of high contributions from the five sources distinguished by PMF. This conclusion was further supported by displaying the PMF outputs on the SOM plane. Furthermore, a corresponding relationship was observed between every factor profile and every trace element group. Our work tests the consistency of the classification (of the trace elements and of the samples) and source identification and improves the application of multiperspective methodology in environmental studies.

Source apportionment and source-to-sink transport of major and trace elements in coastal sediments: Combining positive matrix factorization and sediment trend analysis

Major and trace elemental concentrations in coastal marine sediments were incorporated into positive matrix factorization (PMF) to identify potential sources and source contributions. Transport pathways of fine-grained sediments and sediment-bound elements were inferred from sediment trend analysis (STA). The spatial distribution patterns of 21 elements (Co, Cu, Ni, Sr, Zn, V, Ba, Sc, Ga, Pb, Cr, Zr, SiO₂, Al₂O₃, Fe₂O₃, MgO, CaO, K₂O, MnO, TiO₂, and P₂O₅) coupled with sediment grain sizes were investigated. The natural and anthropogenic sources of the elements were distinguished by their medium enrichment factors (EFs). Seven sources were recognized by PMF: weathering products, anthropologic emissions, sand, older sediment, biogenic carbonates, products of siliceous organisms, and mine exploitation. Some land-derived elements, including weathering products, anthropogenic-related elements, and mining-related elements, had a significant positive correlation with sediment silt, clay, and organic carbon contents. The spatial patterns of the land-derived elements' concentrations and source contributions were consistent with the sediment transport pathways inferred from the STA. This result revealed that the delivery of the land-derived elements was determined by marine current flows and the associated sediment transport processes. Conversely, elements originating from marine sources, such as sand and older sediment, and from the biological activities of calcareous and siliceous organisms showed little response to sediment transport and deposition processes. Our study links the outputs of statistically oriented approaches (e.g., PMF) to a process-based understanding of elemental transport in marine environments.

Detecting long-term temporal trends in sediment-bound metals in the western Adriatic (Mediterranean Sea)

Major and trace metal concentrations were determined in western Adriatic sediment cores. Based on sediment chronology, the earliest anthropogenic influence appeared as a Zn and Pb increase in the Po River prodelta starting from ~1914. The increasing contamination signal of these trace metals propagated southward as far as 450km with a growing delay, taking ~10years to reach the south Adriatic Sea. Although greater inventories of excess trace metals in the northern sector pointed to the influence of the intense human activities in the Po River drainage basin and Venice lagoon system, we observed a reduction of excess trace metals from mid-1980s, related to the implementation of stricter environmental regulations on chemical wastewaters. In contrast, an increase in trace metal accumulation in surficial sediment from the 2000s in front of the cities of Ancona and Bari suggested a recent local input of trace metals, probably due to harbor activities.