Mercury concentration ocean

Thompson DR, Furness RW, Walsh PM. 1992. Historical changes in mercury concentrations in the marine ecosystem of the north and northeast Atlantic Ocean as indicated by seabird feathers. J Appl Ecol 29 79-84. 

Reported mercury values in the oceans determined since 1971 span three orders of magnitude, due at least in part to errors induced by incorrect sampling [62-64]. Olasfsson [65] has attempted to establish reliable data on mercury concentrations obtained in cruises in North Atlantic water. 

In many applications, such as the analysis of mercury in open ocean seawater, where the mercury concentrations can be as small as 10 ng/1 [468,472-476], a preconcentration stage is generally necessary. A preliminary concentration step may separate mercury from interfering substances, and the lowered detection limits attained are most desirable when sample quantity is limited. Concentration of mercury prior to measurement has been commonly achieved either by amalgamation on a noble-metal metal [460,467, 469,472], or by dithizone extraction [462,472,475] or extraction with sodium diethyldithiocarbamate [475]. Preconcentration and separation of mercury has also been accomplished using a cold trap at the temperature of liquid nitrogen. 

Nishimura, M., S. Konishi, K. Matsunaga, K. Hata, and T. Kosuga. 1983. Mercury concentration in the ocean. Jour. Oceanogr. Soc. Japan 39 2951-300. 

Seabird feathers may provide a proxy for oceanic mercury secular change (Monteiro and Furness, 1997). This unique dataset includes feathers retrieved from museum specimens of exclusively pelagic, piscivorous seabirds such as shearwaters and petrels. While there is scatter associated with the values, as should be expected from such a natural archive, an increase of —3 X between 1885 and 1994 can be seen in the mercury concentration of the feathers. Furness, Monteiro and co-workers have extended their work to include studies on the movement of mercury within hving birds and the relationship between prey concentrations of mercury and those observed in the bird s feathers (Monteiro et al., 1998 Monteiro and Furness, 2001), which aid in the interpretation of the feather record. This approach has so far been apphed to the NE... 

A cold-trap pre-concentration procedure, which is incorporated into a standard jlameless atomic absorption analysis of mercury in environmental samples, has been used for both shipboard and laboratory analyses of mercury in seawater, The coefficient of variation for seawater containing 25 ng Hg/l, is 15%, and a detection limit of approximately 0,2 ng Hg is attainable. In surface seawaters of coastal and open regions of the northwest Atlantic Ocean mercury concentrations appear to decrease with increasing distance from terrestrial sources. In the open ocean samples they are less than 10 ng/l. and rather uniformly distributed. The amounts of mercury in inshore samples can approach 50 ng/l, A significant mercury fraction characterized by a stable association with organic material may be present in coastal waters. 

Table II. Mercury Concentrations vs. Depth for Four Stations in the Northwest Atlantic Ocean...

The reported concentrations for mercury in seawater range from non-detectable to 364 ng/1. (11, 12, 15-17, 28-30). In several of these studies, the concentrations of mercury were greater than 100 ng/1. in open ocean waters (12, 28, 29, 30). The data from our investigations of the northwest Atlantic Ocean (Table II) and other studies (11, 15, 16, 17) indicate that the mercury concentrations should be closer to 10 ng/1. in these open ocean waters. 

This variability for the reported concentrations of mercury in open ocean waters may indicate that there are significant analytical diflBculties associated with the proper sample collection and the accurate measurement of mercury in seawater. These problems tend to override and preclude precise geochemical calculations and marine geochemical interpretations regarding the sources, sinks, and interactions of mercury in the oceans. These observational discrepancies for trace seawater constituents such as mercury can be resolved only through intercalibration programs and the use of standardized seawater samples. Such standards are not presently available for mercury concentrations at 100 ng Hg/1. or less in seawater. 

In our previous investigations of the amounts and distribution of mercury in the surface waters of the northwest Atlantic Ocean, we found a mean total mercury concentration of 7 ng/1. and a range of 6-11 ng/1. (26). Also, we found in open ocean surface waters no significant difference between the mercury concentrations measured directly in pre-acidified seawater ( reactive mercury) and the total mercury determination in the organic free samples. In the work shown in Table II, we also found no significant difference between the reactive mercury determination and the total mercury measurement, which was carried out in approximately one third of the samples. The total mercury measurements appear in the square brackets for the results tabulated in Table II. 

As part of the National Oceanic and Atmospheric Administration (NOAA) Status and Trends Program conducted from 1984 to 1987, mercury concentrations were analyzed in four marine bivalve species in U.S. coastal waters (NOAA 1987). Mercury concentrations in bivalve tissues ranged from 0.01 to 0.48 g/g (ppm) dry weight in oysters (Crassostrea virginica), 0.28 to 0.41 g/g (ppm) in the Hawaiian oyster (Ostrea sandwichensis), 0.05 to 0.47 g/g (ppm) in the blue mussel (Mytilus edulis), and 0.04 to... 

Recreational and Subsistence Fishers. Methylmercury concentrations in sport fish can be at least an order of magnitude higher than in commercial fish purchased in a supermarket (see Section 5.4.4). Therefore, recreational and subsistence fishers, including some Native American peoples who consume locally caught fish from mercury-contaminated waterbodies or consume long-lived predatory oceanic species such as shark and swordfish, can be exposed to higher mercury concentrations than individuals who consume similar amounts of commercially marketed fish from a variety of sources (Ebert et al. 1996 ... 

A significant amount of data on mercury concentration in Meditmanean fish has been collected under the UNEP Cowdinated Mediterranean Pollution Monitoring and Research Programme. In general, levels of mercury were higher in fish from the Mediterranean Sea than from the Atlantic, Pacific and Indian Oceans [3]. It could be explained by the fact that active mining sites in the Mediterranean account fw about S0% of the world s production of mercury. 

Slemr E (1996) Trends in Atmospheric Mercury Concentrations over the Atlantic Ocean and at the Wank Summit, and the Resulting Constraints on the Budget of Atmospheric Mercury. In Baeyens W, Ebinghaus R and Vasiliev O, eds. Global and Regional Mercury Cycles Sources, Fluxes and... 

Atmospheric methylmercury precipitated from the atmosphere is usually at less than the 1 pmol level and represents about 1-5% of total mercury. Concentration of methylmercury in the atmospheric gas phase is estimated at 5-25fmolm level. Estimates for a budget of transport fluxes of methylmercury to the oceans have recently been made. Despite these astoundingly small concentrations, amounts in fish and marine animal may be much higher, both absolutely and proportionately (Section 12.13.7.3) arising from transportation effects. 

The combined effect of transpiration from soil and vegetation can be illustrated by the following oversimplified example. With strong westerly winds (25 to 40 km/hr), the concentration of mercury in oceanic air increases from 0.7 to 2 ng/m near California s Central Valley (7), a distance of about 100 km inland from the ocean. With this number the release of mercury per km per day can be calculated. For convenience consider a land section 0.01 km wide with an inversion height of 0.4 km. In this example the distance from the coast to the valley is filled with oceanic air in about 3 hours. The surface which liberates the mercury is thus 1 km, and the corresponding air volume is 0.4 km. Because this volume is swept in 3 hours, the volume swept by oceanic air in 24 hours is 8 times larger or 3.2 km. The mercury increased by 1.3 ng/m. The amount of mercury released over the continent was thus estimated to be ... 

Inshore marine biota often contained higher mercury concentrations than the same or similar species collected offshore. In Sweden, marine fish caught near shore often had elevated methylmercury levels, with many values in the range of 5.0-10.0 mg Hg/kg FW concentrations above 1.0 mg Hg/kg FW in Swedish fish were usually associated with industrial discharges of mercury compounds. In Mediterranean fishes, the mercury body burden was about twice that of conspecifics of the same size from the Atlantic Ocean. It is speculated that the higher body burdens of mercury in Mediterranean species is due to the elevated natural geochemical levels of mercury in the Mediterranean. 

Mercury-selenium interactions are significant in marine mammals and seem to be a factor in loons however, this is not the case in marine birds. Mercury concentrations in oceanic birds were not correlated with selenium concentrations, as evidenced by values in livers of murres, Uria spp. and razorbills Alca torda, and in breast muscle of sooty terns Sterna fuscata. 

Concentrations exceeding 2.0 mg Hg/kg FW in muscle of some wide-ranging oceanic fishes -such as tuna, marlin, and swordfish - were common owing to a combination of human activities and natural processes. For most fish products sold, muscle mercury concentrations were less than 0.3 mg Hg/kg FW however, about 2% of the total catch landed may contain more than 0.5 mg Hg/kg FW. 

McLEAN That s certainly the case. I think that much of the data on the mercury concentrations in atmospheric precipitation are too high. As far as the oceans are concerned, I think oceanographers are the leaders in analytical methodology and contamination control for the determination of mercury in water. The levels of mercury which they are finding in the oceans are now much lower (vAtI-IO ng/liter) than what were being quoted five years ago. 

Mercury is a unique metal. Its oceanic background concentration (Hgx) is very low (< 1 ng/L see also Table 12-1). The risks of rapid changes in speciation, losses and contamination of samples by contact with laboratory air, materials and reagents are high. In contrast to other trace elements, seawater reference materials certified for mercury concentration are not yet available. The quality assurance with regard to accuracy of data is further hampered by the fact that most laboratories, due to the lack of alternative methods, follow almost the same analytical approach. 

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