Tuesday, August 19, 2014

Mercury Pollution Trippled in Oceans Since 1850's

Globally, oceans contain roughly 60,000 to 80,000 tons of mercury pollution, according to a report published this week in Nature detailing the first direct calculation of mercury pollution in the world's oceans. Ocean waters shallower than about 300 feet (100 meters) have tripled in mercury concentration since the Industrial Revolution, the study found, and mercury in the oceans as a whole has increased roughly 10 percent over pre-industrial times. North Atlantic waters showed the most obvious signs of mercury pollution, since surface waters there sink to form deeper water flows. In contrast, the tropical and Northeast Pacific were relatively unaffected. "We don't know what that means for fish and marine mammals, but likely that some fish contain at least three times more mercury than 150 years ago," and possibly more, lead researcher Carl Lamborg of Woods Hole Oceanographic Institution said. "The next 50 years could very well add the same amount we've seen in the past 150." This article @ Yale 360

Abstract from the Nature magazine

Mercury is a toxic, bioaccumulating trace metal whose emissions to the environment have increased significantly as a result of anthropogenic activities such as mining and fossil fuel combustion. Several recent models have estimated that these emissions have increased the oceanic mercury inventory by 36–1,313 million moles since the 1500s. Such predictions have remained largely untested owing to a lack of appropriate historical data and natural archives. Here we report oceanographic measurements of total dissolved mercury and related parameters from several recent expeditions to the Atlantic, Pacific, Southern and Arctic oceans. We find that deep North Atlantic waters and most intermediate waters are anomalously enriched in mercury relative to the deep waters of the South Atlantic, Southern and Pacific oceans, probably as a result of the incorporation of anthropogenic mercury. We estimate the total amount of anthropogenic mercury present in the global ocean to be 290 ± 80 million moles, with almost two-thirds residing in water shallower than a thousand metres. Our findings suggest that anthropogenic perturbations to the global mercury cycle have led to an approximately 150 per cent increase in the amount of mercury in thermocline waters and have tripled the mercury content of surface waters compared to pre-anthropogenic conditions. This information may aid our understanding of the processes and the depths at which inorganic mercury species are converted into toxic methyl mercury and subsequently bioaccumulated in marine food webs.

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