Release of Methyl Mercury from Sediments: Effects of Mercury Concentration, Low Temperature, and Nutrient Addition
01 Nov 1982-Canadian Journal of Fisheries and Aquatic Sciences (NRC Research Press Ottawa, Canada)-Vol. 39, Iss: 11, pp 1459-1466
TL;DR: A flow-through system using plexiglass "microbasins" was used to study methyl mercury release from unpolluted, mercury polluted, and mercury enriched lake and river sediments, suggesting an effect at the sediment–water interface.
Abstract: A flow-through system using plexiglass "microbasins" was used to study methyl mercury release from unpolluted, mercury polluted, and mercury enriched lake and river sediments. Production of methyl mercury ranged up to 3.3 μg∙m−2∙d−1, increasing with increasing mercury content as if following saturation kinetics. It leveled off when mercury content was 15–20 μg Hg/g. An equilibrium between methylating and demethylating mechanisms is suggested. Release at 4 °C was 50–70% of that at 20 °C, which suggests that in polluted Canadian lakes, production in winter may be half the total for the year. Increased methyl mercury release was observed when tryptic soy broth (TSB) was added to sediments at 0.06 or 0.25 g/dm3, and very marked increases when TSB was added to the water flow at 35 mg/L, suggesting an effect at the sediment–water interface.Key words: mercury, methyl mercury, methylation, microbasin, microorganism, sediments, biomethylation
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TL;DR: The current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms is examined in this paper.
Abstract: Mercury is one of the most hazardous contaminants that may be present in the aquatic environment, but its ecological and toxicological effects are strongly dependent on the chemical species present. Species distribution and transformation processes in natural aquatic systems are controlled by various physical, chemical, and biological factors. Depending on the prevailing environmental conditions, inorganic mercury species may be converted to many times more toxic methylated forms such as methylmercury, a potent neurotoxin that is readily accumulated by aquatic biota. Despite a considerable amount of literature on the subject, the behavior of mercury and many of the transformation and distribution mechanisms operating in the natural aquatic environment are still poorly understood. This review examines the current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms.
1,481 citations
TL;DR: This work focuses on the hypothesis that sulfate-reducing bacteria are important mediators of metal methylation in aquatic systems and, moreover, that sulfATE-deposition may stimulate methylmercury production by enhancing the activity of sulfate, reducing bacteria in sediments.
666 citations
TL;DR: Reductions in the organic content of coastal sediment, a potential result of nutrient abatement programs intended to inhibit eutrophication of near-shore waters, could enhance MMHg production by increasing the bioavailability of the large reservoir of "legacy Hg" buried within the sediment.
Abstract: We examined temporal differences in sedimentary production of monomethylmercury (MMHg) at three sites in Long Island Sound (LIS). Sediment-phase concentrations of Hg species decreased from west to east in LIS surface sediments, following the trend of organic matter. However, Hg methylation potentials, measured by incubation with an isotopic tracer (200Hg), increased from west to east. 200Hg methylation potentials were enhanced in August relative to March and June, attributable to differences in activity of sulfate-reducing bacteria. Organic matter and acid-volatile sulfide influenced the distribution coefficient (KD) of inorganic Hg (Hg(II) = total Hg − MMHg) and inhibited 200Hg methylation in surface sediments. 200Hg methylation varied inversely with the KD of Hg(II) and positively with the concentration of Hg(II), mostly as HgS0, in LIS pore waters. Accordingly, we posit that a principal control on MMHg production in low-sulfide, coastal marine sediments is partitioning of Hg(II) between particle and di...
361 citations
TL;DR: In this article, the amount of methylmercury produced in a lake can play a major role in the bioaccumulation of fish from remote, low alkalinity and low pH lakes.
Abstract: Recent studies have demonstrated elevated levels of mercury in fish from remote, low alkalinity and low pH lakes. The mechanisms of this enhanced bioaccumulation are poorly understood, but the amount of methylmercury produced in a lake can play a major role. Decreased pH stimulates methylmercury production at the sediment-water interface and possibly in the aerobic water column. Decreased pH also decreases loss of volatile mercury from lake water and increases mercury binding to particulates in water – factors that may increase methylation at low pH by enhancing the bioavailability of mercury for methylation. In anoxic subsurface sediments, decreased pH decreases the rate of mercury methylation, suggesting that methylmercury formation in the water column and at the sediment-water interface may be most important in acidified lakes. Sulfate-reducing bacteria are important mercury methylators in acidified lakes. Whether enhanced sulfate reduction stimulates methylmercury production in low pH lakes is presently unclear, although most of the available data do not support this hypothesis.
358 citations
TL;DR: Higher water temperatures in smaller lakes during the open-water season influenced M/D ratios and were the cause of higher fish mercury levels.
Abstract: Mercury concentrations in planktivorous, omnivorous, and piscivorous fishes were inversely related to lake size in six lakes in northwestern Ontario. The lakes were remote from direct anthropogenic...
250 citations
References
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TL;DR: The combustion of the fossil fuels coal, oil, and lignite potentially can mobilize many elements into the atmosphere at rates, in general, less than but comparable to their rates of flow through natural waters during the weathering cycle.
Abstract: The combustion of the fossil fuels coal, oil, and lignite potentially can mobilize many elements into the atmosphere at rates, in general, less than but comparable to their rates of flow through natural waters during the weathering cycle. Since the principal sites of fossil fuel combustion are in the mid-latitudes of the Northern Hemisphere, changes in the composition of natural waters and air, as a consequence of this activity, will be most evident at these latitudes.
367 citations
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150 citations
TL;DR: Water analyses in 1968 and 1969 from 40 small lakes within a small area of the Canadian Shield in northwestern Ontario gave mean values for Ca, Na, Mg, and K with mean values of 1.6, 0.9, and 0.4 mg/liter with Ca > Na’s’ Mg” K on a molar basis.
Abstract: Water analyses in 1968 and 1969 from 40 small lakes within a small area of the Canadian Shield in northwestern Ontario gave mean values for Ca, Na, Mg, and K of 1.6, 0.9, 0.9, and 0.4 mg/liter with Ca > Na > Mg > K on a molar basis. HCO3, SO4, and Cl (on a smaller number of samples) were 4.1, 3.0, and 1.4 mg/liter. Total CO2 was variable in the range 0.3–12.0 mg/liter. Specific conductance was in the range 10–35 μmho/cm at 25 C and pH 5.4–7.5. Color was < 5–150 Hazen units, and plant pigments (as chlorophyll a) < 1–21 μg/liter. Total dissolved nitrogen was in the range 110–300 mg N/liter and total dissolved phosphorus 3–20 μg P/liter. NO3-N and PO4-P were often undetectable in summer, and reached winter maxima around 100 and 10 μg/liter.Total dissolved nitrogen and phosphorus contents of five lakes were computed at the beginning and end of periods of several weeks during summer stagnation. Changes were negligibly small in three of the deeper lakes, but the two shallowest showed increases of 0.22 and 0.62 ...
138 citations
TL;DR: A dynamic model for the transport of methyl mercury in a simplified limnic food chain is outlined in this paper, where quantitative influences on these processes of some physico-chemical and biological factors are demonstrated from field investigations and laboratory experiments.
127 citations