Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

17-year study confirms that lead in the soil descends slowly

17.07.2003


In a 17-year experiment on Vermont’s Camel’s Hump, three Dartmouth researchers find that lead moves very slowly though the soil. Using the highly accurate technique of isotopic analysis for the first time at this field site, the researchers traced several varieties of lead with different atomic weights.

Their study was published online on July 12 on the Environmental Science & Technology Web site, a journal of the American Chemical Society.

"This definitively supports a few earlier studies," says Friedland, "that show that lead in forests in the Northeast moves very, very slowly. The lead that was emitted from gasoline and settled into the soil over about 30 or 40 years is not going to end up in our drinking water anytime soon."



This doesn’t mean we should be complacent, say the researchers. The Dartmouth team and others are working on mountains worldwide to discover how soil retains pollutants such as lead and why the lead moves so slowly through the soil.

According to the researchers, lead is one of the most widely dispersed natural contaminants in the world. At elevated levels, it can cause nervous system disorders. In children it has been linked to learning disabilities and other behavioral and developmental problems. Throughout most of the 20th century, people added lead to the atmosphere primarily by burning leaded gasoline, which eventually settled to the earth. High elevation forests, such as the one at Camel’s Hump, are good environmental indicators because they are very sensitive to atmospheric and climate conditions, and they effectively collect lead. Lead pollution is easily intercepted by the leaves on mountain trees, and rain washes it into the soil.

One piece of this study began in 1984 as part of Andrew Friedland’s dissertation research. Friedland, now a Professor and Chair of the Environmental Studies Program at Dartmouth, applied a trace amount of lead over a one-square-meter area in a mountain forest in Vermont. This lead, which was enriched with a stable isotopic signature of 207, is not toxic in small concentrations, and its atomic signature makes it easy to find, even when it descends into the soil.

In 2001, Friedland, James Kaste, a post-doctoral researcher in the Earth Sciences Department and with the Environmental Studies Program, and Stefan Sturup, Director of Dartmouth’s Trace Metal Analysis Core Facility, returned to the exact plot where the lead 207 was applied on Camel’s Hump, a heavily forested, undeveloped mountain near the village of Huntington, Vt. They took soil samples at the site, which is about 200 hundred yards off of a popular hiking trail at an elevation of about 3,300 feet, and brought them to the lab at Dartmouth for analysis.

"We found that the lead 207 applied in 1984 had only moved down into the soil about seven centimeters," says Kaste, the lead author on the paper. "And it will probably move slower in the future because the soil becomes denser. It’s pretty rare to have a long-term study in this field, and here’s a 17-year experiment that we were able to conduct."

Kaste also followed lead 210, which is a natural lead isotope that falls out of the atmosphere. He traced it to learn how long the forest floor, which is the top 10 centimeters of organic material at the top of the soil, retains it. He found that atmospherically deposited lead, like lead 210, will remain in the forest floor between 60 and 150 years, depending on the vegetation.

"The next step is to identify how the lead binds to the soil," he says. "We want to learn if it binds to organic matter, for example, or if it precipitates out."

The researchers explain that their findings are representative of deciduous and coniferous forests throughout much of the Northeastern U.S. and in some areas in Europe and Scandinavia.

"Since the forest floor retains lead for decades and decades," says Kaste, "it could build up if we keep depositing it in levels that would be problematic, so it’s definitely good that we stopped adding lead to our gasoline."

Adds Friedland, "No matter what you do, the natural environment records your history. So we’re leaving a legacy of this spike of lead. It will probably still be there in 500 years."

Sue Knapp | EurekAlert!
Further information:
http://www.dartmouth.edu

More articles from Ecology, The Environment and Conservation:

nachricht How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.

nachricht Using drones to estimate crop damage by wild boars
12.12.2017 | Gesellschaft für Ökologie e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Using drones to estimate crop damage by wild boars

12.12.2017 | Ecology, The Environment and Conservation

How fires are changing the tundra’s face

12.12.2017 | Ecology, The Environment and Conservation

Telescopes team up to study giant galaxy

12.12.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>