Mercury's Toxic Threat: Understanding Water Pollution

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury.

Mercury pollution is a global concern due to its ubiquitous nature

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Due to this natural mercury cycle, irrespective of which part of the world releases mercury, it could affect an entirely different part of the world, making mercury pollution a global concern. Mercury pollution is now identified as a global problem and awareness has been raised on an international action plan to minimize anthropogenic mercury emissions and clean up mercury pollution. The 2002 Global Mercury Assessment concluded that "International actions to address the global mercury problem should not be delayed".

Mercury pollution is caused by the direct discharge of industrial wastes, mining wastes, or naturally occurring mercury minerals. Although there has always been some mercury in the atmosphere from natural sources (volcanoes), human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Reduction and oxidation of mercury mostly occur closer to the ocean water surface. These are either driven by sunlight or by microbial activity. Under UV radiation, elemental mercury oxidizes and dissolves directly in ocean water or binds to other particles. The reverse reaction reduces some mercury Hg2+ to elemental mercury Hg(0) and returns to the atmosphere. Fine aerosols in the atmosphere such as ocean water droplets can act as small reaction chambers in this process providing the special reaction conditions required.

Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury. Plankton absorb methylmercury from the water and sediment. Fish eat contaminated plankton and smaller fish, and the methylmercury accumulates in their tissues. Methylmercury formed by bacterial action on ionic mercury (Hg(II)) is far and away the leading environmental contaminant for consumption advisories of fish in the United States, as well as globally. This is because mercury emissions are ubiquitous, and almost no other contaminant bioaccumulates to the extent of methylmercury. Typical bioconcentration factors are a million- to a hundred million-fold more than water concentrations, giving levels of toxicological concern even in the most remote sections of the planet.

Mercury pollution is a global concern because of its ubiquitous nature. Mercury emissions are ubiquitous, and almost no other contaminant bioaccumulates to the extent of methylmercury. Typical bioconcentration factors are a million- to a hundred million-fold more than water concentrations, giving levels of toxicological concern even in the most remote sections of the planet. Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Due to this natural mercury cycle, irrespective of which part of the world releases mercury, it could affect an entirely different part of the world, making mercury pollution a global concern.

Mercury emissions are ubiquitous and almost no other contaminant bioaccumulates to the extent of methylmercury

Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury. Plankton absorb methylmercury from the water and sediment. Fish eat contaminated plankton and smaller fish, and the methylmercury accumulates in their tissues. Methylmercury formed by bacterial action on ionic mercury (Hg(II)) is far and away the leading environmental contaminant for consumption advisories of fish in the United States, as well as globally. This is because mercury emissions are ubiquitous, and almost no other contaminant bioaccumulates to the extent of methylmercury. Typical bioconcentration factors are a million- to a hundred million-fold more than water concentrations, giving levels of toxicological concern even in the most remote sections of the planet.

Some water bodies also receive mercury from direct discharge of industrial wastes, mining wastes, or naturally occurring mercury minerals. Although there has always been some mercury in the atmosphere from natural sources (volcanoes), human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Reduction and oxidation of mercury mostly occur closer to the ocean water surface. These are either driven by sunlight or by microbial activity. Under UV radiation, elemental mercury oxidizes and dissolves directly in ocean water or binds to other particles. The reverse reaction reduces some mercury Hg2+ to elemental mercury Hg(0) and returns to the atmosphere. Fine aerosols in the atmosphere such as ocean water droplets can act as small reaction chambers in this process providing the special reaction conditions required. Oxidation and reduction of mercury in the ocean are not very simple reversible reactions.

Mercury can be turned into a highly toxic form called methylmercury through biological processes

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury. Plankton absorb methylmercury from the water and sediment. Fish eat contaminated plankton and smaller fish, and the methylmercury accumulates in their tissues.

Reduction and oxidation of mercury mostly occur closer to the ocean water surface. These are either driven by sunlight or by microbial activity. Under UV radiation, elemental mercury oxidizes and dissolves directly in ocean water or binds to other particles. The reverse reaction reduces some mercury Hg2+ to elemental mercury Hg(0) and returns to the atmosphere. Fine aerosols in the atmosphere such as ocean water droplets can act as small reaction chambers in this process providing the special reaction conditions required. Oxidation and reduction of mercury in the ocean are not very simple reversible reactions.

Some water bodies also receive mercury from direct discharge of industrial wastes, mining wastes, or naturally occurring mercury minerals. Although there has always been some mercury in the atmosphere from natural sources (volcanoes), human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Methylmercury formed by bacterial action on ionic mercury (Hg(II)) is far and away the leading environmental contaminant for consumption advisories of fish in the United States, as well as globally. This is because mercury emissions are ubiquitous, and almost no other contaminant bioaccumulates to the extent of methylmercury. Typical bioconcentration factors are a million- to a hundred million-fold more than water concentrations, giving levels of toxicological concern even in the most remote sections of the planet.

Ocean water droplets can act as small reaction chambers in the reduction and oxidation of mercury

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Due to this natural mercury cycle, irrespective of which part of the world releases mercury, it could affect an entirely different part of the world, making mercury pollution a global concern. Mercury pollution is now identified as a global problem and awareness has been raised on an international action plan to minimize anthropogenic mercury emissions and clean up mercury pollution. The 2002 Global Mercury Assessment concluded that "International actions to address the global mercury problem should not be delayed".

Some water bodies also receive mercury from the direct discharge of industrial wastes, mining wastes, or naturally occurring mercury minerals. Although there has always been some mercury in the atmosphere from natural sources (volcanoes), human activities have increased the amount of mercury emitted to, and deposited from the atmosphere.

Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury. Plankton absorb methylmercury from the water and sediment. Fish eat contaminated plankton and smaller fish, and the methylmercury accumulates in their tissues.

Reduction and oxidation of mercury mostly occur closer to the ocean water surface. These are either driven by sunlight or by microbial activity. Under UV radiation, elemental mercury oxidizes and dissolves directly in ocean water or binds to other particles. The reverse reaction reduces some mercury Hg2+ to elemental mercury Hg(0) and returns to the atmosphere. Fine aerosols in the atmosphere such as ocean water droplets can act as small reaction chambers in this process providing the special reaction conditions required. Oxidation and reduction of mercury in the ocean are not very simple reversible reactions. Shown below is the proposed pathway of ocean aerosol mercuric photochemistry suggesting that it occurs through a reactive intermediate: Photo oxidation is suspected to be driven by OH.

Sunlight and microbial activity drive the reduction and oxidation of mercury in the ocean water surface

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Some water bodies also receive mercury from direct discharge of industrial wastes, mining wastes, or naturally occurring mercury minerals. Once mercury is in the water, biological processes can turn it into a highly toxic form called methylmercury. Plankton absorb methylmercury from the water and sediment. Fish eat contaminated plankton and smaller fish, and the methylmercury accumulates in their tissues.

Reduction and oxidation of mercury mostly occur closer to the ocean water surface. These are either driven by sunlight or by microbial activity. Under UV radiation, elemental mercury oxidizes and dissolves directly in ocean water or binds to other particles. The reverse reaction reduces some mercury Hg2+ to elemental mercury Hg(0) and returns to the atmosphere. Fine aerosols in the atmosphere such as ocean water droplets can act as small reaction chambers in this process providing the special reaction conditions required. Oxidation and reduction of mercury in the ocean are not very simple reversible reactions.

The 2002 Global Mercury Assessment concluded that "International actions to address the global mercury problem should not be delayed". Mercury emissions are ubiquitous, and almost no other contaminant bioaccumulates to the extent of methylmercury. Typical bioconcentration factors are a million- to a hundred million-fold more than water concentrations, giving levels of toxicological concern even in the most remote sections of the planet.

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