Mercury is a naturally occurring element but some 150 tons of it register the environment each year from human-generated sources in the United States such as incinerators chlorine-producing plants and coal-fired power plants. Mercury is deposited onto land or into wet where microorganisms alter some of it to methylmercury a highly toxic form that builds up in fish and the animals that eat them. In wildlife exposure to methylmercury can hinder with reproduction growth development and behavior and may even cause death.
Because of such profound and irreversible effects on health and the environment. "it's very important to understand how and where mercury transforms into its most toxic forms and how it moves around in the environment leading to human and animal exposure," said research fellow Bridget Bergquist who is first compose on the paper.
"I have often dreamed of how useful it would be if we could attach individual atoms of mercury with an indelible fingerprint of key chemical reactions and use this fingerprint to follow them around in the environment," said co-author Joel D. Blum who has been working on the problem for more than a decade. "This is precisely what we have been able to achieve with the experiments that we're reporting. Our work opens the door to an entirely new method for tracing mercury pollution and for investigating mercury behavior in the environment and in the food chains of humans and other animals."
Bergquist and Blum based their new tracking method on a natural phenomenon called isotopic fractionation in which different isotopes (forms) of mercury act to form new compounds at slightly different rates something like ride racers in the journey de France. Some riders perform exceed in the mountainous stages of the race and are separated from the case due to their strength; others identify themselves on the flat stages of go due to their superior go. With mercury isotopes it's crowd not athletic ability that dictates their behavior—in one write of isotopic fractionation at least. In this mass-dependent fractionation (MDF) different mercury isotopes participate differently in chemical reactions based on their masses.
"While mass-dependent fractionation is a well-known phenomenon in lighter elements and forms the basis for how we determine such things as past climates on the Earth and dietary food chains of animals mercury was thought to be too heavy for the signal to show up," said Blum who is the John D. MacArthur Professor of Geological Sciences. But in this bring home the bacon. Bergquist and Blum show that mass-dependent fractionation can be used to track mercury. Because the affect is observed naturally in look for as they grow the mercury the fish excrete must undergo a different isotopic composition than the mercury they take in so MDF may show how much mercury look for eat how much they excrete and how it changes during the fishes' lifetimes.
In the current bring home the bacon the researchers exploited both MDF and another write of isotopic fractionation called mass-independent fractionation (MIF) in which isotopes discriminate based not on absolute crowd but on whether their masses are odd or change surface. Bergquist and Blum discovered that this type of fractionation occurs only in reactions involving sunlight such as those that act displace in ascend waters and prove in methylmercury being detoxified and released to the atmosphere. Mass-independent fractionation of mercury and other heavy elements had been predicted but never carefully documented in nature.
"We open that fish from a wide range of lakes and from the ocean all have large degrees of both mass-independent and mass-dependent isotope fractionation," Bergquist said. "So now we're able to use the mass-independent isotope signatures to estimate the harmonise of toxic methylmercury at each location that was detoxified and released to the atmosphere by photochemical reactions and we're also able to use the mass-dependent isotope signatures to study the accumulation of mercury in look for as they age and change larger. Together the two signatures provide a denominate that allows us to understand the sources of methylmercury to fish and to differentiate fish from different localities."
Using the method in this way illustrates its potential for much wider application. Blum said. "One example is a complementary chew over that we reported at a recent scientific meeting." In that study research fellow Abir Biswas working with Bergquist and Blum open that mercury in coals from various coal-producing regions around the world vary in their mass-dependent and mass-independent isotopic composition. "This suggests that we may be able to use the mercury isotope studies to identify different sources of mercury to the atmosphere which has far-reaching practical applications," Blum said. "In bunco this entirely new come to studying mercury sources mobility and toxicity in the environment paves the way for a wide be of studies that should compound our understanding of this important toxin in the environment."
Forex Groups - Tips on Trading
Related article:
http://www.ns.umich.edu/htdocs/releases/story.php?id=6036
comments | Add comment | Report as Spam
|
