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Global assessment of the mercury pollutants in the oceans

The human contribution to environmental pollution or what is known as the anthropogenic factor has been cited in a ground breaking study released today, according to the journal Nature.

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It has long been known that there is toxic mercury which has contaminated seafood. Oceanographer Carl Lamborg with the Woods Hole Oceanographic Institutions in Massachussetts led an international team across the Atlantic, Pacific, Southern and Arctic oceans over the past 8 years collecting water samples at various depths to find the levels of mercury.

Since it is expensive and time consuming to collect seawater samples a program named GEOTRACES, whose mission is to study the trace elements and isotopes in the ocean, funded the project. The team began its collection for studies at various depths in the oceans.

Lamborg and his team began with a benchmark by using 1000 meters in the Pacific Ocean. This would allow them to compare the mercury concentration in samples across the oceans in their research selection.

The research report released today concluded that Mercury amounts of 60,000-80,000 tons are in the oceans. The highest concentration of mercury resides in shallow waters at depths of less than 1000 meters. The concentration of mercury has tripled since the pre-industrial era. This higher mercury concentration in shallower waters increases the toxin in fish which humans are eating according to the study's conclusion of marine web food.

The most vulnerable area for people lies in the countries around the North Atlantic, since it has the highest recorded levels in the study. How high is the danger level? The scientists do not know how much of the mercury transforms into toxic methyl mercury.

In the 1950’s there was a strange neurological epidemic that killed thousands of villagers in the seaside town of Minamata, Japan due to high mercury levels in the fish. The mercury was dumped by a local chemical plant.

On the California coast of the United States, the California Gold Rush of the 1850s’s was a major source of mercury run off into the oceans from the rivers. Liquid mercury was heated and used to obtain the gold from the ore. It was allowed to vaporize in the process and fall into the earth. Lamborg hypothesizes in his study that the collection in the soil at the time ran off into the ocean over time from erosion.

As of January 2013, over 100 countries have participated in the Minamata Convention. This international treaty works to reduce mercury emission levels through measures such as banning new mercury mines.

Lamborg's team studied the levels of greenhouse gas carbon dioxide as a comparison, so they could ascertain what was truly human contribution and not natural breakdown of rocks. The existing databases of CO2 measured in ocean waters allowed the team to develop an index relating the two substances. This allowed them to conclude the level of human production responsible for the mercury runoff into the oceans.

David Streets, an environmental policy scientist at Argonne National Laboratory in Lemont, Illinois, finds that this empirical data is impressive and states, “This is the first time, to my knowledge, that a group [has] tried to give an overview of all the major ocean areas.” He concluded: “It’s a valuable data set.”

Lamborg states: “I hope that these data will help countries in terms of assessing how badly we need to regulate mercury emission.”

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