18th April 2011 Paper and Carbon-13

Why study carbon-13 uptake by trees?

The uptake of carbon-13 instead of carbon-12 by plants is dependent on environmental conditions, and as such is an indicator of environmental changes. Plants prefer carbon-12 over carbon-13. When photosynthesis is intense, they have to use carbon dioxide which contains carbon-13.  Due to the burning of fossil fuels, themselves low in carbon-13, the fraction of carbon-13 compared with carbon-12 in the air has decreased.

How can carbon-13 uptake be measured?

When testing trees for the amount of carbon-13 in atmospheric carbon dioxide, scientists have to take samples from many trees from different places. It can also be measured by using ice cores.

So what's new?

Instead of travelling the world in search of trees, Prof. Dan Yakir, Weizmann Institute of Science, went to the library. He took samples from magazines and newspapers dated 1880-2000. These magazines were from two European and two American publishers. He analysed the amount of carbon-13 in these paper samples to see if they reflected the changes in environment caused by fossil fuel burning.

Why does this matter?

The analysis of the carbon-13 content of the paper showed that its concentration in the atmosphere has decreased demonstrating the increased use of fossil fuels. The change in the carbon-13 levels in paper are consistent with the carbon-13 levels in the air and tree rings. This means that the technique could perhaps be used to provide data for climate scientists.  If independent sources for air levels of carbon-13 are available, then this technique could be used to date manuscripts.

Sources

Weizmann Institute of Science: Pollution history preserved in paper
Reading between the lines: Papers report on global change
Wikipedia: Suess effect