Mercury Concentration In Seawater Research Articles

Multi-proxy record of the mid-Maastrichtian event in the European Chalk Sea: Paleoceanographic implications

The Cretaceous provides us with an excellent case history of ocean-climate-biota system perturbations. Such perturbations occurred several times during the Cretaceous, such as oceanic anoxic events and the end-Cretaceous mass extinction, which have been the subject of an abundant literature. Other perturbations, such as the mid-Maastrichtian Event (MME) remain poorly understood. The MME was associated with global sea-level rise, changes in climate and deep-water circulation that were accompanied by biotic extinctions including ‘true inoceramids’ and the demise of the Caribbean-Tethyan rudist reef ecosystems. So far, the context and causes behind the MME remain poorly studied. We conducted high-resolution integrated biotic, petrological and geochemical studies in order to fill this knowledge gap. We studied, in particular, carbonate Nd and Os isotopes, whole-rock Hg, C and N content, C and N isotopes in organic matter, S isotopes in carbonate-associated sulfate, along with C and O isotopes in foraminifera from the European Chalk Sea: the Polanówka UW-1 core from Poland and the Stevns-1 core from Denmark. Our data showed that sea-level rise of ∼50–100 m lasted around ∼2 Ma and co-occurred with anomalously high mercury concentration in seawater. Along with previously published data, our results strongly suggest that the MME was driven by intense volcanic–tectonic activity, likely related to the production of vast oceanic plateaus (LIP, Large Igneous Province). The collapse of reef ecosystems could have been the consequence of LIP-related environmental stress factors, including climate warming, presumably caused by emission of greenhouse gases, modification of the oceanic circulation, oceanic acidification and/or toxic metal input. The disappearance of the foraminifer Stensioeina lineage on the European shelf was likely caused by the collapse of primary production triggered by sea-level rise and limited amount of nutrient input. Nd isotopes and foraminiferal assemblages attest for changes in sea-water circulation in the European Shelf and the increasing contribution of North Atlantic water masses.

HR3DHG version 1: modeling the spatiotemporal dynamics of mercury in the Augusta Bay (southern Italy)

Abstract. The biogeochemical dynamics of Hg, and specifically of its three species Hg0, HgII, and MeHg (elemental, inorganic, and organic, respectively), in the marine coastal area of Augusta Bay (southern Italy) have been explored by the high-resolution 3D Hg (HR3DHG) model, namely an advection–diffusion–reaction model for dissolved mercury in the seawater compartment coupled with a diffusion–reaction model for dissolved mercury in the pore water of sediments in which the desorption process for the sediment total mercury is taken into account. The spatiotemporal variability of the mercury concentration in both seawater ([HgD]) and the first layers of bottom sediments ([HgDsed] and [HgTsed]), as well as the Hg fluxes at the boundaries of the 3D model domain, have been theoretically reproduced, showing acceptable agreement with the experimental data collected in multiple field observations during six different oceanographic cruises. Also, the spatiotemporal dynamics of the total mercury concentration in seawater have been obtained by using both model results and field observations. The mass balance of the total Hg species in seawater has been calculated for the Augusta Harbour, improving previous estimations. The HR3DHG model could be used as an effective tool to predict the spatiotemporal distributions of dissolved and total mercury concentrations, while contributing to better assessing hazards for the environment and therefore for human health in highly polluted areas.

A cross-sectional study of exposure to mercury in schoolchildren living near the eastern seaboard industrial estate of Thailand.

Industrial activity in Thailand's coastal areas has significantly increased mercury concentrations in seawater, causing accumulation through the food chain. Continuous exposure to mercury has been linked to bioaccumulation in living organisms and potential adverse health effects in children. Blood samples were collected from 873 schoolchildren aged 6-13 years living in four sites near the eastern seaboard industrial estates of the Gulf of Thailand in 2011. Total mercury level in whole blood (Hg-B) was compared with standard reference values. Mean (± standard deviation) concentrations of Hg-B from schoolgirls (2.19 ± 0.5 μg/L; n = 405) and schoolboys (2.29 ± 0.3 μg/L; n = 468) did not exceed the regulatory limits of the United States Environmental Protection Agency (US EPA), the German Commission on Human Biological Monitoring (HBM I, II) or Clarke's analysis of drugs and poisons reference values. Nevertheless, 67 children (34 girls and 33 boys) had individual values that exceeded the lowest of these standards (4 μg/L). The relatively low concentrations of Hg-B detected in this study suggested a relatively low risk for schoolchildren. However, 67 children had elevated mean total Hg-B concentrations, especially in the two sites located nearest the industrial area. This information may serve as an early warning of the potential for pollution to affect children living around industrial areas. Further regular monitoring, including studies assessing the health impact of mercury pollution in this region of Thailand, is to be encouraged.

Complexation of dimethylsulfide with mercuric ion in aqueous solutions

The tendency of dimethylsulfide (DMS) to form complexes with heavy metal ions in aqueous solutions and the factors that influence it have been investigated. Among five heavy metal ions examined (Cu2+, Cd2+, Zn2+, Pb2+ and Hg2+), only Hg2+ bound significantly with DMS in aqueous solutions in which Hg2+ concentration was increased to much higher levels than that of natural seawater. The complexation capacity of Hg2+ for DMS was influenced by pH and media. The affinity of Hg2+ for DMS was generally lower at high than at low pH, presumably due to the competition of hydroxide ion to form hydroxomercury species. In different solutions, the affinity of Hg2+ for DMS followed the following sequence: ultra-purified water > 35‰ NaCl solution > seawater. It seems apparent that chloride had a negative impact on the complexation of DMS by Hg2+, owing to the competition of chloride with DMS for complexing Hg2+. In addition, the affinity of Hg2+ for DMS in the bulk seawater appeared to be higher than that in the surface microlayer seawater. The tendency of Hg2+ to form complexes with DMS in aqueous solution can be reduced by the presence of 2 mM amino-acid such as glycine, alanine, serine and cysteine, as these ligands give stable mercury complexes. However, the presence of 2 mM acetate in experimental solutions had no significant effect on the complexation of Hg2+ with DMS, even though this ligand has a relatively strong complexing capacity for Hg2+. Although mercury ions appeared to have a strong affinity for DMS, the concentration of mercury in seawater is too low to produce a great effect on the distribution of DMS in oceans.

Mercury concentrations in seawater, sediments and wild mussels from the coast of Galicia (NW Spain)

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Detection of localized methylmercury contamination by use of the mussel adductor muscle in Minamata Bay and Kagoshima Bay, Japan

Based on our previous finding that the concentrations of total mercury in mussel adductor muscle approximated those of methylmercury, we compared concentrations of total mercury in the adductor muscle of the mussel Mytilus galloprovincialis, collected from four sites around Minamata City from 1993 to 1995 and four sites in Kagoshima Bay from 1997 to 1998, to assess the level of localized methylmercury contamination. Though the input of mercury from the chemical plant had stopped by around 1970, concentrations of total mercury in the mussel adductor muscle were higher at two sites (26–121 ng/g, n=135) near the main fallout of wastewater from the chemical plant in Minamata Bay than at the other sites, i.e. two sites 1–5 km from the former sites in Minamata City (6–28 ng/g, n=52), and all sites in Kagoshima Bay (2–30 ng/g, n=287). The localized methylmercury contamination around the chemical plant in Minamata Bay was documented also by our sensitive analysis of mercury concentrations in seawater and sediment samples. The survey of concentrations of total mercury in the mussel adductor muscle seems to be useful for monitoring the methylmercury contamination in coastal areas.

Optimization of sampling and analytical procedures for the determination of mercury at sub‐ng.1‐1 levels in sea water

Abstract Cold‐vapour atomic absorption spectrophotometry (CVAAS) was used to determine mercury concentrations in sea water from the British Channel and the North Sea. Experiments were carried out to study the stability of the samples during storage and to investigate contamination from the Niskin‐satnplers used. Mercury concentrations ranged from 0.28 to 1.5 ng.l‐1 for Atlantic and for North Sea water. Somewhat higher values (up to 3.7 ng.l‐1) were found in coastal areas. There was also a significant input from the rivers Scheldt and Thames.

Posidonia as an indicator of mercury contamination

The mercury content in the marine phanerogam Posidonia oceanica, sampled in an area near a chloralkali complex, has been measured and compared with that of the samples collected in a non-impacted region. Plants growing in the seawater facing the chlor-alkali complex showed mercury content of 0.19 μg g −1 f.w., compared with 0.02 μg g −1 f.w. in the samples from the control area. Sediments of the industrial area have mercury levels 20–30 times higher than those from the control area. As the mercury concentration in seawater of both areas is comparable, the mercury content in the plant appears to be correlated with mercury levels in the sediment; probably the metal uptake in Posidonia oceanica takes place mainly through the root system.

Direct determination of mercury in sea-water by anodic stripping voltammetry with a graphite electrode

In recent determinations of mercury in sea-water, methods such as spectrophotometry [ 1, 21, atomic absorption spectrometry with cold vapour techniques as well as with flameless techniques [ 3, 41, and neutron activation analysis [4, 51 have been employed extensively in conjunction with various pm-treatment procedures. Because of the extremely low concentration of mercury in sea-water (usually a few to 100 ng Hg l-l), the sample size normally taken must be relatively large (O-5-5 1 or more) in order to achieve satisfactory accuracy. Anodic stripping voltammetry (asv.) has been applied to mercury determinations by Perone and Kretlow [ 6] and by Luong and Vydra [ 71, who used, respectively, a graphite electrode and a rotating glassy carbon electrode. The sensitivity of their methods seems to be too low for the direct analysis of sea-water. Allen and Johnson [8] , using a rotating system with a platinum ring and a glassy carbon disc, attained a detection limit of about 10 ng Hg 1-l in the sulfuric acid medium, but the applicability of this method to sea water has yet to be proved. An attempt to apply a.s.v. with the graphite electrode to direct measurements of mercury in sea-water has proved successful when a perchloric acid solution is used as the stripping medium. The procedure described below permits the determination of mercury concentrations as low as 5 ng Hg l-l, in 50-ml samples with minimum pre-treatment.

Mercury in the Kuroshio and Oyashio regions and the Japan Sea

ALTHOUGH measurements of the mercury concentration in sea water have been made by several investigators1–13, the reported values are widely scattered and it may be significant that almost all the samples were kept in polyethylene bottles after acidification. Weiss et al.14 have reported that the main source of mercury in the oceans was the degassing of the Earth's crust by way of the atmosphere. It should then be supposed that the large experimental variations for open oceans does not reflect the true situation.