Distribution pattern of mercury in northern Barents Sea and Eurasian Basin surface sediment.

Marine sediment is a significant sink for the global pollutant mercury. In a rapidly changing Arctic region, mercury (Hg) bioaccumulation in the marine ecosystem remains a prominent environmental issue. Here, we report surface sediment (0-2 cm) concentrations of Hg and other toxic elements of interest (Cr, Ni, Zn, Cu, As, Cd, Pb) in the northern Barents Sea and Eurasian Basin. We observed average Hg concentrations of 65 ± 23 ng/g with the highest concentration of 116 ng/g in the Eurasian Basin. Our calculated enrichment factors suggest low anthropogenic enrichment for mercury, chromium, nickel, and copper. Mercury and trace element geographic patterns are best explained by the origin and transportation of fine grain sediment towards the Eurasian Basin, with scavenging by both particulate organic carbon and metal oxides as significant delivery mechanisms.

Climate change mitigation effects: How do potential CO2 leaks from a sub-seabed storage site in the Norwegian Sea affect Astarte sp. bivalves?

Carbon capture and storage (CCS) is one of the most promising mitigation strategies for reducing the emissions of carbon dioxide (CO2) to the atmosphere and may substantially help to decelerate global warming. There is an increasing demand for CCS sites. Nevertheless, there is a lack of knowledge of the environmental risk associated with potential leakage of CO2 from the storage sites; and even more, what happens when the seepage stops. Can the environment return to the initial equilibrium? Potential effects on native macrofauna were studied under a scenario of a 50-day CO2 leakage, and the subsequent leak closure. To accomplish the objective, Trondheim Fjord sediments and clams were exposed to an acidified environment (pH 6.9) at 29 atm for 7 weeks followed by a 14-day recovery at normal seawater conditions (pH 8.0, 29 atm). Growth and survival of clams exposed to pressure (29 atm) and reduced pH (6.9) did not significantly differ from control clams kept at 1 atm in natural seawater. Furthermore, bioaccumulation of elements in the soft tissue of clams did not register significant variations for most of the analysed elements (Cd, Cr, Pb, and Ti), while other elements (As, Cu, Fe, Ni) had decreasing concentrations in tissues under acidified conditions in contrast to Na and Mg, which registered an uptake (Ku) of 111 and 9.92 µg g-1dw d-1, respectively. This Ku may be altered due to the stress induced by acidification; and the element concentration being released from sediments was not highly affected at that pH. Therefore, a 1 unit drop in pH at the seafloor for several weeks does not appear to pose a risk for the clams.

Trace metal mobility in sub-seabed sediments by CO2 seepage under high-pressure conditions.

Carbon capture and storage (CCS) is the third contributor to cumulative carbon emission reductions required by the second half of this century. Although this is a promising technology for reducing atmospheric CO2, it is only affordable if the confinement of the gas is guaranteed for hundreds of years. Hence, it is of paramount importance to figure out and predict the chemical and biological effects associated with potential CO2 leakage, to provide decision makers with a good basis for choosing technology and potential storage sites. To this end, a titanium reactor (1.4 m3) was used to study CO2 seepage under realistic sub-seabed conditions (30 bar pressure and 7 °C). The injection of CO2 was calibrated to decrease the pH value from 8.1 to 7.3, which may be the pH found near a leakage point. This pH value also coincides with predictions for near-future ocean pH under current CO2 emissions worldwide. The results from this study demonstrate that there are some elements, i.e., Fe, Co, Pb, Ce, Zn and Cu, present in deep marine sediments, that are strongly affected by the reduced pH levels related to CO2 addition. The dissolved concentrations of Fe, Pb and, to a lesser extent, Cr increased, due probably to weakening of the Fe/Mn shuttle by increased dissolved concentrations of CO2. Desorption processes from oxyhydroxide surfaces due to acidification may explain the release of Co, Ni and Ce observed during the experiment. The increased CO2 concentration also led to increased metal bioavailability, suggested by higher values for labile metal species. Conversely, Cd mobility seems not to be affected by CO2-associated acidification. It is concluded that the determination of those elements most affected by CO2-related acidification in a sub-seabed CO2 storage perimeter (i.e., sediment, sediment-water interface and water column) would be a simple and effective technique to verify suspected leakage.

Anthropogenic impact on marine ecosystem health: A comparative multi-proxy investigation of recent sediments in coastal waters.

Hazardous substances entering the sea, and ultimately deposited in bottom sediments, pose a growing threat to marine ecosystems. The present study characterized two coastal areas exposed to significant anthropogenic impact - Gulf of Gdansk (Poland), and Oslofjord/Drammensfjord (Norway) - by conducting a multi-proxy investigation of recent sediments, and comparing the results in light of different available thresholds for selected contaminants. Sediment samples were analyzed for benzo(a)pyrene (B(a)P) and other polycyclic aromatic hydrocarbons (PAHs), nonylphenols (NPs), organotin compounds (OTs), toxic metals (Cd, Hg, Pb), as well as mutagenic, genotoxic and endocrine-disrupting activities (in CALUX bioassays). In general, a declining trend in the deposition of contaminants was observed. Sediments from both basins were not highly contaminated with PAHs, NPs and metals, while OT levels may still give rise to concern in the Norwegian fjords. The results suggest that the contamination of sediments depends also on water/sediment conditions in a given region.

Effects of experimental CO2 leakage on solubility and transport of seven trace metals in seawater and sediment.

The impact of CO(2) leakage on solubility and distribution of trace metals in seawater and sediment has been studied in lab scale chambers. Seven metals (Al, Cr, Ni, Pb, Cd, Cu, and Zn) were investigated in membrane-filtered seawater samples, and DGT samplers were deployed in water and sediment during the experiment. During the first phase (16 days), "dissolved" (<0.2 microm) concentrations of all elements increased substantially in the water. The increase in dissolved fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb in the CO(2) seepage chamber was respectively 5.1, 3.8, 4.5, 3.2, 1.4, 2.3 and 1.3 times higher than the dissolved concentrations of these metals in the control. During the second phase of the experiment (10 days) with the same sediment but replenished seawater, the dissolved fractions of Al, Cr, Cd, and Zn were partly removed from the water column in the CO(2) chamber. DNi and DCu still increased but at reduced rates, while DPb increased faster than that was observed during the first phase. DGT-labile fractions (Me(DGT)) of all metals increased substantially during the first phase of CO(2) seepage. DGT-labile fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb were respectively 7.9, 2.0, 3.6, 1.7, 2.1, 1.9 and 2.3 times higher in the CO(2) chamber than that of in the control chamber. Al(DGT), Cr(DGT), Ni(DGT), and Pb(DGT) continued to increase during the second phase of the experiment. There was no change in Cd(DGT) during the second phase, while Cu(DGT) and Zn(DGT) decreased by 30% and 25%, respectively in the CO(2) chamber. In the sediment pore water, DGT labile fractions of all the seven elements increased substantially in the CO(2) chamber. Our results show that CO(2) leakage affected the solubility, particle reactivity and transformation rates of the studied metals in sediment and at the sediment-water interface. The metal species released due to CO(2) acidification may have sufficiently long residence time in the seawater to affect bioavailability and toxicity of the metals to biota.