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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