Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Atmospheric Mercury Has Declined -- But Why?

10.06.2003

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. This welcome decline may result from control measures undertaken in western Europe and North America, but scientists who have just concluded a study of atmospheric mercury say they cannot reconcile the amounts actually found with current understanding of natural and manmade sources of the element.

An international group of scientists, led by Franz Slemr of the Max Planck Institute for Chemistry [Max-Planck-Institut fuer Chemie] 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 ship transatlantic ship cruises since 1977. They have published their findings 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. These observations accord well, the researchers say, with data on mercury deposited in peat bogs and found in ice cores.

Scientists have believed that natural processes and human activities put about equal amounts of mercury into the atmosphere. Assuming that natural emissions and re-emissions of the historically deposited mercury have remained constant, the observed reduction of about 17 percent in concentration from 1990 to 1996 would have to result from a reduction of about 34 percent in manmade emissions during that period. This, the scientists say, is three to four times larger than the 10 percent decrease in manmade emissions suggested by previous studies. Therefore, either our understanding of manmade emissions or of the ratio of natural to manmade emissions probably has to be refined, they say.

The level of atmospheric mercury is important, even though at current levels, it is not directly toxic. 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."

Further, Slemr says, some of the atmospheric mercury is deposited into soil and water, where it can be "transformed to methyl mercury, one of the most toxic compounds." In ocean water, methyl mercury concentrates in plankton and further accumulates 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.

Therefore, the researchers say, it is essential that we better understand the amount and sources of mercury in the atmosphere. The amount of mercury emitted naturally is not well understood at present. With regard to manmade emissions, coal burning definitely emits mercury, and it was recently discovered that biomass burning is another important source. Waste incineration is also a source, but not yet well quantified. Further, says Slemr, the annual re-emission of a small fraction of the 200,000 metric tons of mercury deposited into the environment since Roman times is uncertain.

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. Further research will be necessary with regard to the quantitative and qualitative sources of atmospheric mercury, both natural and manmade, for any emission inventory to be credible.

The study was funded in part by the Deutsche Forschungsgemeinschaft.

Harvey Leifert | AGU

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>