Mercury accumulation in the sediment of the Western Mediterranean abyssal plain: A reliable archive of the late Holocene

Kwon

et al. 2021

ACS Earth Space Chem.

Despite the large climatic fluctuations in the Arctic over the Holocene, the dominant mercury (Hg) sources and the potential changes in Hg sources associated with the climate remain unclear. Here, we use Hg isotopes to reconstruct changes in Hg sources and processes in two Svalbard fjord sediment cores spanning the Holocene. The Hg isotope ratios of the fjord sediment cores are similar to bedrock and Hg bound to terrestrial total organic carbon (TOC) but different from other sediment cores influenced by atmospheric Hg drawdowns via the sinking of marine particulate organic matter. The absence of significant Hg and TOC relationships indicates that bedrock erosion caused by glacier dynamics is the major Hg source to the fjord sediment rather than those bound to marine and terrestrial TOC. Measurable shifts in Hg sources are observed at regional cooling (4.3 ka) and during the Medieval Warm Period in the late Holocene. The negative shift in δ202Hg (by −0.5‰) at 4.3 ka from baseline (∼10 ka) is consistent with the rapid increase in glacier-mediated physical and chemical erosions of bedrock. The significant positive shifts in δ202Hg (by 0.5‰) in the late Holocene are explained by enhanced input of atmospheric Hg and its drawdown via the sinking of marine particulate organic matter and some anthropogenic influence, which suppressed the positive Δ199Hg and Δ200Hg shifts. This study suggests that Hg isotope ratios measured in sedimentary archives can be used to decipher climate and other local to global changes modifying Hg sources in the Arctic.

Section: Resultscontrasting

confidence: 82%

Climate-Associated Changes in Mercury Sources in the Arctic Fjord Sediments

Kwon

et al. 2021

ACS Earth Space Chem.

“…The use of Hg stable isotopes allowed us to suggest anthropogenic sources for Hg in Mediterranean surface sediments. 104 A recent paper 105 shows that Hg accumulation rates rose from 0.4 to 8.6 μg m −2 y −1 in the last 6000 years, with a maximum deposition in the last 120 years. According to the same authors, the accumulation rate for the year 2001−2002 measured with a sediment trap, located 20 m above abyssal sediments, was 3.1 ± 0.5 μg m −2 y −1 and suggests Hg fluxes to the deep WMED sediments of 4.2 Mg y −1 .…”

Section: Updating the Mediterranean Hg Cyclementioning

confidence: 99%

Mediterranean Mercury Assessment 2022: An Updated Budget, Health Consequences, and Research Perspectives

Cossa

Knœry

Bănaru

et al. 2022

Environ. Sci. Technol.

Mercury (Hg) and especially its methylated species (MeHg) are toxic chemicals that contaminate humans via the consumption of seafood. The most recent UNEP Global Mercury Assessment stressed that Mediterranean populations have higher Hg levels than people elsewhere in Europe. The present critical review updates current knowledge on the sources, biogeochemical cycling, and mass balance of Hg in the Mediterranean, and identifies perspectives for future research especially in the context of global change. Concentrations of Hg in the Western Mediterranean average 0.86 ± 0.27 pmol L -1 in the upper water layer and 1.02 ± 0.12 pmol L -1 in intermediate and deep waters. In the Eastern Mediterranean, Hg measurements are in the same range but are too few to determine any consistent oceanographical pattern. The Mediterranean waters have a high methylation capacity, with MeHg representing up to 86 % of the total Hg, and constitute a source of MeHg for the adjacent North Atlantic Ocean. The highest MeHg concentrations are associated with low oxygen water masses suggesting a microbiological control on Hg methylation, consistent with the identification of hgcAlike genes in Mediterranean waters. MeHg concentrations are twice as high in the waters of the western basin compared to the ultra-oligotrophic eastern basin waters. This difference appears to be transferred through the food webs and the Hg content in predators to be ultimately controlled by MeHg concentrations of the waters of their foraging zones. Many Mediterranean top-predatory fish still exceed European Union 2 regulatory Hg thresholds. This underlines the necessity of monitoring the exposure of Mediterranean populations, to formulate adequate mitigation strategies and recommendations, without advising against seafood consumption. This review also points out other insufficiencies of knowledge of Hg cycling in the Mediterranean Sea, including temporal variations in air-sea exchange, hydrothermal and cold seep inputs, point sources, submarine groundwater discharge, and exchanges between margins and the open sea. Future assessment of global change impacts under the Minamata Convention Hg policy requires long-term observations and dedicated high-resolution Earth System Models for the Mediterranean region.atmosphere, surface, and deep marine waters have increased respectively by 450, 230, and 12-25 % above levels prevailing during the pre-Colombian period 11 , i.e., before ~1450 CE. This budget however presents large uncertainties, in particular, local differences are to be expected, due to specific geographical, geological, biological, and anthropogenic factors.The GMA 2018 1 also stresses that Mediterranean (MED) populations tend to have higher Hg levels than people from Asia, North America, and Europe. Already, 50 years ago, high Hg levels were observed in MED fish and marine mammals 17, 18 , and these findings have been confirmed several times 19, 20, 21 . It has been recently suggested that Hg accumulation rates in bluefin tuna are the highest in the individuals fro...

Global Biogeochemical Cycles

“…These estimates are 2‐fold higher than those of coastal regions with lower sedimentation rates (<0.5 g cm −2 yr −1 ), such as the coasts of Northern Europe (including the Baltic Sea and Portuguese margin; 57.4 μg m −2 yr −1 , n = 9; Leipe et al., 2013; Mil‐Homens et al., 2009) and the coasts of Russia (the Laptev, Siberian, and Chukchi Seas; 31.5 μg m −2 yr −1 , n = 3; Aksentov et al., 2021; Fox et al., 2014; D. V. Kim et al., 2023), as well as the coasts of Antarctica (the Ross Sea; 14.1 μg m −2 yr −1 ; Zheng et al., 2015). The contemporary Hg‐AR in the ECMS is approximately 4‐ and 5‐fold higher than the global median (∼80 μg m −2 yr −1 ), one to two orders of magnitude larger than other coastal oceans in the world with relatively low MAR (0.02–0.1 g cm −2 yr −1 ; Figure S9 in Supporting Information S1), and the currently estimated deep‐ocean average of 0.7–10.4 μg m −2 yr −1 (Cossa et al., 2021; Outridge et al., 2018; Sanei et al., 2021; Y. X. Zhang et al., 2015). Especially, the Yangtze River Estuary ranks as one of the coastal oceans' largest hotspots for Hg burial (∼1,052 ± 120 μg m −2 yr −1 ; cores DH‐1 (R. Zhang et al., 2018) and DH3‐1 (this study) between 2015 and 2016).…”

Section: Discussionmentioning

confidence: 90%

“…V. Kim et al, 2023), as well as the coasts of Antarctica (the Ross Sea; 14.1 μg m −2 yr −1 ; Zheng et al, 2015). The contemporary Hg-AR in the ECMS is approximately 4-and 5-fold higher than the global median (∼80 μg m −2 yr −1 ), one to two orders of magnitude larger than other coastal oceans in the world with relatively low MAR (0.02-0.1 g cm −2 yr −1 ; Figure S9 in Supporting Information S1), and the currently estimated deep-ocean average of 0.7-10.4 μg m −2 yr −1 (Cossa et al, 2021;Outridge et al, 2018;Sanei et al, 2021; Y. X. Zhang et al, 2015).…”

Section: Burial Flux Of Mercurymentioning

confidence: 86%

“…High‐resolution sedimentary records of Hg accumulation in the nine sediment cores (M3, M7, H28, C0307, FFJ103, DH3‐1, DH3‐2, C0803, and DH5‐1) can provide well‐defined natural and anthropogenic Hg burial fluxes in the ECMS. Notably, these ratios of anthropogenic to preindustrial were low‐bound on the ratios of anthropogenic to natural (Selin, 2018), given the impact of human activities on a longer timescale (i.e., prior to 2000 BCE; Amos et al., 2013; Cossa et al., 2021). Using the relative fractions of anthropogenic Hg estimated from sediment cores, the excess inventories that were scaled to the total areas of the ECMS seafloor, and the total sedimentary inventory of Hg in surface sediments, the total amounts of anthropogenic Hg accumulated in the BS, YS, and ECS were estimated to be approximately 9.7 ± 6.9 Mg yr −1 , 7.2 ± 5.3 Mg yr −1 , and 19.0 ± 20.8 Mg yr −1 (∼35.9 ± 33.1 Mg yr −1 in total), respectively (Figure 6b).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Mercury Burial in Modern Sedimentary Systems of the East China Marginal Seas: The Role of Coastal Oceans in Global Mercury Cycling

Sun,

Hu,

Sun

et al. 2023

Coastal oceans, the transition zones between terrestrial and oceanic systems, are susceptible to anthropogenic mercury (Hg) inputs and are regarded as critical dynamic interfaces of the global Hg cycle. However, the extent to which coastal oceans are accountable for sequestering Hg remains largely unknown owing to a lack of data on high‐resolution Hg accumulation in marine sediments. Synthesizing the results of this study (eight cores and 212 surface sediments) and the literature (three cores and 149 surface sediments), we provide a quantitative evaluation of the biogeochemical cycle of sedimentary Hg in the East China Marginal Seas (ECMS), including the response of the coastal marine sediments to anthropogenic disturbance as well as both human‐derived and natural Hg burial fluxes. We find a linear increase in Hg accumulation since the 1950s (2.0 ± 2.5% yr‐1) and a decline in Hg accumulation between 2010 and 2016. Modern burial fluxes of total and anthropogenic Hg in the ECMS (covering ∼4.8×105 km2 of sea surface) were estimated to be 89.1 ± 48.3 and 35.9 ± 33.1 Mg yr‐1, respectively. Using a compilation of 688 surface sediments and 131 sediment cores (819 samples in total) distributed globally in coastal oceans, we estimate that approximately 1,590 (range: 1,190–2,760) Mg yr‐1 (Method 1) and 540 (range: 310–960) Mg yr‐1 (Method 2) Hg are accumulated in coastal ocean regions. Our findings suggest that coastal oceans are likely the largest global marine sinks for Hg and play a dominant role in regulating the oceanic Hg cycle and budgets.