Posted on 06/11/2003 11:24:02 AM PDT by cogitator
cientists Puzzled by Decline of Atmospheric Mercury
WASHINGTON, DC, June 10, 2003 (ENS) - Though the amount of gaseous mercury in the atmosphere has dropped sharply from its peak in the 1980s and has remained relatively constant since the mid-1990s, scientists cannot figure out why it has declined.
The lower numbers, the scientists say, may result from control measures undertaken in western Europe and North America, but a scientific study of atmospheric mercury says they cannot reconcile the amounts actually found with current understanding of natural and human sources of the element.
An international group of scientists, led by Franz Slemr of the Max Planck Institute for Chemistry in Mainz, Germany, studied the worldwide trend of total gaseous mercury at six sites in the Northern Hemisphere, two sites in the Southern Hemisphere and on eight transatlantic ship cruises since 1977. Their findings were published in "Geophysical Research Letters," a journal of the American Geophysical Union.
The fixed sites ranged from the Canadian Arctic to Antarctica. In both hemispheres, total gaseous mercury increased in the late 1970s, apparently peaked in the late 1980s, decreased to a minimum in the mid-1990s and has remained relatively constant since then.
Concentrations in the Southern Hemisphere are about one-third less than in the Northern Hemisphere, which fits well with data on mercury deposited in peat bogs and found in ice cores, the researchers found.
The level of atmospheric mercury is important even though it is not directly toxic at current levels. The problem, says Slemr, "is that some 5,000 metric tons of atmospheric mercury are currently deposited worldwide every year. The atmospheric lifetime of elemental mercury is about one year and, thus, the mercury is deposited even in remote areas."
Some of the atmospheric mercury is deposited into soil and water, Slemr says, where it can be "transformed to methyl mercury, one of the most toxic compounds."
In ocean water, methyl mercury concentrates in plankton and in fish, especially those high in the food chain, such as tuna. High methyl mercury levels in tuna can lead to chronic diseases in persons who eat the fish, with pregnant women most in danger.
Slemr and his colleagues conclude that future emission inventories must take into account the difference between atmospheric mercury levels in the Northern and Southern hemispheres, as well as the historic and present day emission trends.
I gave that a chemical chuckle.
Next thing you know, some Economist will say actual events were higher, lower or unexpected as related to his well studied prediction. (giving him a 100% batting average).
Last night's weather forecast may have even been wrong.
We're heroes, I suppose. Except to the fish.
But, seriously, the EPA isn't being totally candid in this regard.
Not known to the general public, but all the mercury glass fever thermometers were recalled in 1968 because they were all contaminated with tuna.
Which of course explains the spike and subsequent decline...it was an anomoly caused by tons of tuna burdened mercury being crushed at secret EPA recycling centers in Hoboken and Palm Springs.
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