September 1, 2010

Synchrotron Detects Black Carbon

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With a 768 meter circumference and the capability to send electrons and positrons flying at 99.9999995 percent the speed of light, the Cornell High Energy Synchrotron Source (CHESS) attracts more than 500 scientists per academic year. One such scientist, Ph.D. candidate Karen Heymann, crop and soil sciences, used the university’s synchrotron to research and analyze one of the world’s “dirtiest” specimens – soil.

“Black carbon” is a form of carbon, formed through the incomplete combustion of fossil fuels and other carbon-containing compounds.  It is frequently found in human-made and naturally-occurring soot, either in the atmosphere or the soil.  Black carbon may increase global warming by absorbing heat in the atmosphere and reducing the Earth’s ability to reflect sunlight.

Because soil is abundant in black carbon, it plays an important role in global carbon cycling. While the detection and chemical characterization of black carbon has posed difficulty for scientists in the past, Heymann shared an effective testing technique in her recent seminar, “Black Carbon in Soil and Material Matter.”

“Typical techniques include spectroscopic approaches like FTIR or NMR. FTIR is a qualitative technique for analyzing soil carbon, while NMR is a quantitative technique for characterization of soil carbon. Both of these are problematic because they require a lot of pretreatment of the soil sample, which might alter our findings,” Heymann explained.

For more accurate results, Heymann recommended performing near-edge X-ray fine edge structure spectroscopy with a synchrotron, like the CHESS. “If we use the synchrotron for detection and research, we don’t have to pre-treat the sample. It is very ‘point and shoot.’ It detects all the carbon by using the x-rays as a light source and exciting all the protons within the atoms. It’s very precise.”

According to Heymann, detecting and characterizing black carbon in soils is extremely important because soils contain the largest pool of organic carbon in terrestrial ecosystems, and can thus have a multitude of effects on global carbon budgets and the environment.

Some scientists, like Heymann, believe black carbon is valuable. One particularly controversial type of black carbon is biochar, which results after some biomass is heated in the absence of oxygen until in decomposes in a process called “pyrolysis.”  Biochar has multiple uses as a soil amendment.

“Biochar provides the structural habitat needed for a rich community of microorganisms to take hold,” Heymann said. “The use of biochar has been shown to increase water retention, microbial activity, uptake of minerals by plants, as well as continued deposition of healthy soil,” she added.

Opponents of biochar as a soil amendment argue that it will lead to the exploitation of forests for carbon trading. “People tend to glorify harmony with nature, or maybe they fear corporate control,” she said.

Heymann explained that moral and political discourse often occurs due to a lack of understanding of scientific fact. “Such discourse only polarizes the subject, and doesn’t give people the opportunity to look at the science,” she said. “There is no need for such discourse because it only hinders progress in the research.”

Original Author: Maria Minsker