Deployment of the Woods Hole Oceanographic Institution giant gravity corer during United States Geological Survey cruise 2008008FA aboard the National Oceanic and Atmospheric Administration research vessel Figure 4.
Example of field lithologic log, which contains core location and visual sediment description data collected during United States Geological Survey cruise 2008008FA aboard the National Oceanic and Atmospheric Administration research vessel Figure 5.
The study, published in the current online edition of Nature Geoscience, examined the radiocarbon content of river sediments collected from the Ganges-Brahmaputra system draining the Himalayas.
The basin, the scientists say, "represents one of the largest sources of terrestrial biospheric carbon to the ocean." Using radiocarbon dating, WHOI researchers Valier Galy and Timothy Eglinton found that organic carbon resides in the basin for anywhere from 500 to 17,000 years.
Because of the fossil fuel effect, this is not actually the activity level of wood from 1950; the activity would have been somewhat lower.
The fossil fuel effect was eliminated from the standard value by measuring wood from 1890, and using the radioactive decay equations to determine what the activity would have been at the year of growth.
Carbon dating has been used since the 1940s to determine the ages of archaeological finds.
Modern methods in mass spectrometry, far advanced since their development in the 1970s, now enable carbon dating to be applied to a wide range of new problems.
More traditional uses of carbon dating also benefit from an AMS, because it provides more precise measurements of carbon-14 than other methods, and it can do so with incredibly tiny samples -- as small as 1 milligram.
An accelerator mass spectrometer measures the amounts of different isotopes within a sample.
For carbon dating, the process starts in an ionizing chamber, where the atoms within a sample of pure carbon are given a negative charge.
The upper Kali Gandaki River drains semi-arid and scarcely vegetated regions north of the Himalayan Range, where conditions promote very long organic carbon residence time in soils.
Credit: Valier Galy, Woods Hole Oceanographic Institution (Phys Org.com) -- Woods Hole Oceanographic Institution (WHOI) scientists have found that carbon is stored in the soils and sediments of the Ganges-Brahmaputra basin for a surprisingly long time, making it likely that global warming could destabilize the pool of carbon there and in similar places on Earth, potentially increasing the rate of CO2 release into the atmosphere.