Processes driving heavy metal distribution in the seawater of an Arctic fjord (Hornsund, southern Spitsbergen)

How atmospheric deposition contribute to watershed heavy metals contamination in coastal watersheds in China: A case study of Laizhou Bay

Atmospheric deposition is a significant source of heavy metal (HM) pollution. In order to understand the migration and transformation process of atmospheric HMs within the watershed and quantify the amount transported offshore by rivers, the Soil and Water Assessment Tool (SWAT) was developed to trace the migration of HMs from atmospheric deposition. The model simulates HMs in three forms: dissolved, adsorbed, and granular. It quantifies the movements of Cd, Cr, Cu, Hg, Pb, and Zn from atmospheric deposition into the sea via rivers in five coastal watersheds in East China and analyzes the effects of meteorological factors, vegetation cover, and slope on non-point pollution of these metals by Spearman correlation analysis. The results showed that the annual flux of HMs from atmospheric deposition to the sea through rivers accounted for 5 %-69 % of the total rivers flux. Among meteorological factors, precipitation demonstrated the strongest correlation with the monthly loads of HMs entering rivers from atmospheric deposition. Additionally, HMs loads entering rivers from atmospheric deposition were more closely related to vegetation cover than topographic slope. This model provides a new approach to distinguishing the flux of atmospheric HMs entering offshore waters through rivers. The findings will deepen our understanding of the migration and transformation of HMs from atmospheric deposition, enhance the ability to control offshore HMs pollution, and reduce the ecological risks associated by HMs.

Heavy metals and Pb isotopes in sediment cores from the Bering and Chukchi seas: Implications for environmental changes and human activities over the past century

The Bering Sea and the Chukchi Sea are important regions for marine ecosystems and climate change. However, the historical deposition and sources of metals in these regions are poorly understood. In this study, we utilized Pb isotopes and multi-element concentrations (Ni, Cu, Fe, Mn, Zn, Cd, Pb) coupled with Pb-210 dating to investigate the historical deposition and source identification of metals in sediment cores collected from the Bering Sea and the Chukchi Sea. Our findings reveal that the transport of organic matter was mainly transported by marine and terrestrial sources in the Bering and Chukchi Sea, respectively. Historical variations of metals were similar in both seas, showing an increasing trend of metals (excluding Mn) from the 1960s to the 1990s, followed by a gradual decrease after the 1990s, which can be attributed to the development of industrial and gasoline emission. The results of the geo-accumulation index indicated that sediment in both seas was relatively unpolluted with metals. Additionally, Pb isotopic ratios suggested that natural weathering was the primary source of Pb in the area, but the use and phase-out of gasoline were also well-reconstructed. This study provides valuable information for assessing environmental changes and human activities over the past century in the Arctic and subarctic Ocean.

Trace metals in surface water of the Pechora River and its tributaries: Content, water quality and risks assessment (Arctic Ocean basin)

The article is devoted to the study of trace metals content in the Pechora River and its tributaries, which is the largest river in the Arctic Ocean basin. The study of physico-chemical properties of water showed aerobic conditions of low-mineralised water with pH values suitable for drinking water. Analysis of the content of trace metals has revealed that the main flow of Al, Mn, Co, Cu, Zn, V, As, Mg and Fe into the Pechora River comes from its tributaries. The average content of Cr, Mn, Cu, Zn, Pb, V, As, Mg and Fe in the water of the Pechora River delta was higher than for the main river channel, which indicates the transfer of a large mass of trace metals to the Barents Sea and the Arctic water ecosystem. For the studied river and tributaries, chronic pollution of the Pechora River with Al, Mn, Ba, Fe, Cu, U and Pb metals has adverse effects on waterborne organisms. The degree of contamination of natural waters by metals has been assessed using water quality indices (TMPI, TMEI, TMTI) and public health risks (HI and CR). Low contamination and weak toxicity of the Pechora River water has been determined, but serious contamination, toxicity and high non-carcinogenic risk of some of its tributaries have been observed. A high carcinogenic risk has been established for the consumption of all water sampled. Al, Ni, As, Fe, Mn, Cr, Cd, and Ba were found to be the highest priority contaminating trace metals. At present, contamination of the Pechora River and its tributaries with trace metals is formed under the influence of dissolution processes of rocks of the Ural Mountains, the Taminsky Ridge, underlying mineral deposits, permafrost degradation processes and glacier melting. Anthropogenic factors include oil and gas production and transportation.

Shell mineralogy and chemistry - Arctic bivalves in a global context

This study provided new data on shell mineralogy in 23 Arctic bivalve species. The majority of examined species had purely aragonitic shells. Furthermore, we measured concentrations of Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn in 542 shells representing 25 Arctic bivalve species. Species-related differences in concentrations of specific elements were significant and occurred regardless of locations and water depths. This observation implies the dominance of biological processes regulating elemental uptake into the skeleton over factors related to the variability of abiotic environmental conditions. Analysis of the present study and literature data revealed that the highest concentrations of metals were observed in bivalves collected in the temperate zone, with intermediate levels in the tropics and the lowest levels in polar regions. This trend was ascribed mainly to the presence of higher anthropogenic pressure at temperate latitudes being a potential source of human-mediated metal pollution.

Distribution of Trace Metals in Ice and Water of Liaodong Bay, China

Trace metal pollution in coastal seas has been of great concern because of its persistence, toxicity, and biological accumulation through the food chain. The role of sea ice in trace metal transport and distribution in Liaodong Bay is still unknown. Sea ice and water samples were collected in Liaodong Bay in February 2021 to assess the distributions of Cu, Pb, Cd, Zn, Cr and Hg during the frozen season. Total dissolved (<0.45 μm) and particulate (>0.45 μm) heavy metal concentrations were measured by atomic absorption spectrophotometry (Cu, Pb, Cd, Zn and Cr) and atomic fluorescence spectrophotometer (Hg). The ice held significantly higher levels of total Cr when compared to water. There were no significant differences in total concentrations of Cu, Pb, Cd, Zn and Hg between water and ice samples. An analysis of dissolved-to-total metal ratios shows that all studied metals in the dissolved phase, except Hg, are found exclusively in Liaodong Bay nearshore ice as a result of desalination. Concentrations of particulate metals are higher in sea ice than in seawater due to suspended/bed sediment entrainment and atmospheric deposition. The partitioning coefficients of six trace metals are not increased with the increase in the concentration of particulate matter in sea ice due to sediment accumulation. The redistribution of trace metals between seawater and ice was a result of comprehensive effects of physico-chemical processes and environmental factors, such as chemical oxygen demand, salinity, and suspended particulate material.

Spatial distribution and risk assessment of metal(loid)s in marine sediments in the Arctic Ocean and Bering Sea

Seventy-four surface sediment samples were collected from the Arctic Ocean and Bering Sea to determine the content of metal(loid)s (As, Cu, Cd, Ni, Pb, Zn and Cr). Metal(loid)s content in these sediments varied from 2.36-41.90 mg/kg for As, 8.63-82.28 mg/kg for Cu, 0.14-0.71 mg/kg for Cd, 11.86-100.60 mg/kg for Ni, 8.30-27.58 mg/kg for Pb, 39.93-391.43 mg/kg for Zn, and 40.96-106.49 mg/kg for Cr. The pH and water-soluble organic carbon content had considerable impacts on the content of metal(loid)s in sediment, but the texture of sediment has limited influence on metal(loid)s content in sediment. In addition, the hotspots of most of these metal(loid)s appeared in the Beaufort Sea region. The geoaccumulation index (I_geo) indicated that Cd was the metal with the highest contamination in these sediments, with 55.41% of the sample sites posing moderate pollution. The ecological risk for As, Cu, Ni, Pb, Zn and Cr indicates low ecological risk (100%), while Cd posed moderate risk (35.14%), considerable risk (54.05%) and high risk (10.81%) and attributed more than 76.45% of the total potential ecological risk of these metal(loid)s.

Sources, fate and distribution of inorganic contaminants in the Svalbard area, representative of a typical Arctic critical environment-a review

Global environmental changes not only contribute to the modification of global pollution transport pathways but can also alter contaminant fate within the Arctic. Recent reports underline the importance of secondary sources of pollution, e.g. melting glaciers, thawing permafrost or increased riverine run-off. This article reviews reports on the European Arctic-we concentrate on the Svalbard region-and environmental contamination by inorganic pollutants (heavy metals and artificial radionuclides), including their transport pathways, their fate in the Arctic environment and the concentrations of individual elements in the ecosystem. This review presents in detail the secondary contaminant sources and tries to identify knowledge gaps, as well as indicate needs for further research. Concentrations of heavy metals and radionuclides in Svalbard have been studied, in various environmental elements since the beginning of the twentieth century. In the last 5 years, the highest concentrations of Cd (13 mg kg-1) and As (28 mg kg-1) were recorded for organic-rich soils, while levels of Pb (99 mg kg-1), Hg (1 mg kg-1), Zn (496 mg kg-1) and Cu (688 mg kg-1) were recorded for marine sediments. Increased heavy metal concentrations were also recorded in some flora and fauna species. For radionuclides in the last 5 years, the highest concentrations of 137Cs (4500 Bq kg-1), 238Pu (2 Bq kg-1) and 239 + 240Pu (43 Bq kg-1) were recorded for cryoconites, and the highest concentration of 241Am (570 Bq kg-1) was recorded in surface sediments. However, no contamination of flora and fauna with radionuclides was observed.

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.

Generation of a novel transgenic marine medaka (Oryzias melastigma) for highly sensitive detection of heavy metals in the environment

As typic priority pollutants in the marine environment, heavy metals can be accumulated in the human body leading to serious environmental and health problems. The metal regulatory elements (MREs) have been identified to be the main functional parts for the response to heavy metals. To develop a convenient biological monitoring tool for the detection of heavy metals in the oceans, we generated a transgenic marine medaka line Tg(OmMT: eGFP) with a truncated metallothionein promoter, which was only 193 bp and drove the expression of eGFP. After Tg(OmMT:eGFP) embryos were treated with four different heavy metals and different concentrations, the results showed that the expression level of eGFP was consistent with that of the endogenous mt. The transgenic embryos are very sensitive to Hg²⁺, and the fluorescence could be induced in the 0.0002 μM concentration, which is far lower than the primary water standard. The expression level of eGFP and mt showed a dose-dependent manner to heavy metals concentration. Taken together, the newly established marine medaka is a sensitive, efficient, and convenient tool for monitoring heavy metal pollution in the environment, especially seawater.