Measure mercury residues in the South China Sea

A measurement campaign carried out on marine research vessels suggests that mercury diffused into and out of the sea in the South China Sea is high, seasonal changes and worrisome.

Mercury is a strong neurotoxin. It enters the atmosphere when burning coal and during the exploitation of precious metals. Flying by wind, Hg dissolves into sea water, appears and concentrates most and is most dangerous in seafood, especially big fish. But Hg from the sea water is also evaporated out.

In order to determine the Hg flux in and out of the sea, the team led by Chun-Mao Tseng of Taiwan National University in Taipei and Carl Lamborg of the Woods Hole Oceanographic Institute in Massachusetts conduct a very sophisticated measurement test.

From 2003 to 2007, they and their colleagues across the South China Sea measured the seasonal variation. The South China Sea is the ideal place for this survey. One is because coal-fired thermal power plants are very dense in southern China, and the South China Sea weather changes seasonally.

Indeed, when Tseng and Lamborg analyzed the measurement data, they found that the data varied seasonally. In the winter, when the sea surface temperature is low and the monsoon is strong, the South China Sea transforms into a net sink of Hg in the melted atmosphere. In the summer, when meteorological conditions reverse, the South China Sea acts as a source of Hg emissions into the atmosphere. Every year, the emission source is stronger than the dissolved amount.

Although the South China Sea accounts for only 1% of the world's sea surface, it accounts for 2.6% of global emissions. Although the net flux, Tseng and Lamborg found that Hg concentrations dissolved in the South China Sea at least nine times more than the ocean.