Mercury, coastal sediment levels

O2 concentrations, such as found in marine wetlands. High biomethylation rates have also been observed in coastal sediments. Because methylmercury is transferred up the food chain, the marine fish that occupy high trophic levels have very high mercury concentrations. In some cases, such as for tuna and swordfish, concentrations are high enough to pose human health risks. 

Bottom sediments in the coastal zone of the sea may be polluted with copper, zinc, nickel and cadmium. The highest levels of toxic heavy metals are found in the mouths of rivers. The bottom sediments in the Black Sea have a high mercury level—from 0.28 to 0.40 pg/1. In the coastal waters of the Krasnodar Territory the mercury level is 0.15-1.55 pg/1, while its maximum concentrations are registered in the Danube and Dnieper mouth areas. The Danube alone brings annually up to 50-60 tons of mercury, while the Dnieper brings up to 5 tons. The distribution of heavy metals in bottom sediments in the Russian shelf of the Black Sea is not uniform. Their greatest quantities are accumulated in sediments in the deepest part of the shelf where their concentration is 3-5 times higher than in sediments in the shallower part. Toxic metals contained in sea water in the dissolved and suspended forms are ac-... 

The use of stable isotopes of mercury to track pathways of inputs and uptake is innovative. The additions will be increased over time to levels comparable to the current mercury deposition in the northeastern US. The work is ongoing and, as of 2002, one paper has been published (Hintelmann et al., 2002). We wish to reemphasize that in productive near-shore regions of marine ecosystems, the legacy of pollution derived mercury in the surficial sediments is likely to predominate over new mercury as a substrate for methylation. The intense bioturbation in coastal marine sediments can keep much historical mercury active, relative to the more quiescent sediments of lakes. Unfortunately, the mechanistic predictions for declines in fish mercury levels following controls on mercury emissions, derived from the anticipated successful METAALICUS program, will not be applicable to the marine environment. 

Mercury is a dynamic element, and its chemical behavior in waters, sediments, and soils is complex and is influenced by several factors. These factors include redox, pH, salinity, alkalinity, hardness, and organic matter (i.e., composition, reactivity, concentration, etc.). As with other metals, sediments and soils serve as the main reservoirs for Hg consequently, the levels, distribution, and speciation of Hg in these media must be established to understand its complex behavior. In Table 2, we present selected data on Hg levels that exist in coastal, marine, lagoonal, and estuarine sediments from distinct regions of Mexico. These data show that sediments... 

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