Pollution from the Stratosphere
By Dave Armstrong - 19 Dec 2011 18:24:0 GMTNow oxidised mercury seems to be raining down on us, especially in certain parts of America and near the tropics. Recently, the Dead Sea was found to have one of the highest oxidised mercury levels outside the polar regions. The upper troposphere and the lower stratosphere present an ideal reaction site for the oxidation of mercury that finds its way there on microscopic particles. "The upper atmosphere is acting as a chemical reactor to make the mercury more able to be deposited to ecosystems," said Seth, who did the work as a research assistant professor in science and technology at the University of Washington Bothell.
It's possible that the ozone there could more easily oxidise the metal in a reaction. The model developed by him shows a rapid loss of elemental mercury from the stratosphere. The authors then suggest sedimentation of the mercury, along with the entrainment processes that occur by convection, causing the stratosphere to dump the HgO (oxidised mercury) in certain regions such as the SW United States. These pollutant areas have the climatic conditions to receive the oxidised mercury which will have originated thousands of miles away before its ascent and descent as described.
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