Archive for September 2013

The Threat of Terrestrial Carbon

September 17, 2013
Dr. Margaret Torn at an NGEE field test site near Council, Alaska. Lawrence Berkeley National Laboratory – Roy Kaltschmidt, photographer.

Dr. Margaret Torn at an NGEE field site near Council, Alaska. Photo: Lawrence Berkeley National Laboratory – Roy Kaltschmidt, photographer.

In the northernmost city of the United States – Barrow, Alaska – the treeless flat tundra looks stark and forbidding to many people. The permanently frozen soil (permafrost) is only capable of supporting plants like moss, heather and lichen and the temperatures can drop as low as -60 °F.

However, this tundra is a mecca for climate scientists like Dr. Margaret Torn, co-lead of the Climate and Carbon Sciences Program at Lawrence Berkeley National Laboratory (Berkeley Lab). Torn just returned from performing field experiments near Barrow. She is part of the 10-year Next-Generation Ecosystem Experiment, a large collaboration of scientists and engineers who are trying to better understand the Arctic terrestrial ecosystem so they can improve vital climate predictions. These scientists are finding new ways to study the complex ecosystem of the Arctic landscape, including looking deep into the soil.

“Soil is a big mystery,” explained Torn. “We don’t understand why soil holds so much carbon. And we don’t understand how a warming climate will affect soils. The question being whether a warming climate will result in carbon transferring from soils to the atmosphere as greenhouse gases, creating additional global warming.”

Soils are an important part of the carbon cycle. In the natural carbon cycle, carbon dioxide is taken up by plants and photosynthesized. If the plants aren’t harvested for food or fuel, they decay and their organic matter makes its way to the soil where it is processed by tiny microbes – bacteria and fungi – that release the carbon dioxide back into the atmosphere.

Soils are critical because they store about 2.3 trillion tons of carbon – more than twice as much as the atmosphere or vegetation. In comparison, burning fossil fuels releases about 9 billion tons of carbon dioxide per year.

Soils are also a long-term reservoir of carbon. Carbon cycles very slowly deep in the soil, where it can remain for 50,000 years. So a critical question is how long will soils contain these rich deposits of carbon? Will the carbon stay put? Or will it enter the atmosphere in the near future, greatly amplifying climate change?

The Arctic tundra is an area that is particularly worrisome. Cold temperatures suppress microbial growth, which helps trap the vast stores of carbon in the soil. But global warming is causing the Arctic permafrost to thaw, triggering the microbes to become active and respire carbon dioxide into the atmosphere.

Equipment Ron and her team use to sample greenhouse gases flowing from the land to the atmosphere. They later determine how old the carbon is in these gas samples using carbon-14 dating. Photo: Margaret Torn.

Equipment Torn and her team use to sample greenhouse gases flowing from the land into the atmosphere. They later determine how old the carbon is in these gas samples using carbon-14 dating. Photo: Margaret Torn.

Torn’s group drills wells in the Alaskan ground to directly measure the flow of carbon dioxide and methane from the land to the atmosphere. They measure these gas flows in areas where the permafrost is intact and where it is thawing, trying to understand the environmental variables that are controlling the release of greenhouse gases.

They see very high methane concentrations in areas where the permafrost is thawing. However, this summer they found that in some areas specialized microbes consume this methane before it is released, so carbon dioxide is released into the atmosphere instead. This is good news for the environment, because carbon dioxide is a less potent greenhouse gas than methane.

They also take soil core samples from different regions in Barrow, and then incubate them at different temperatures back home at Berkeley Lab. They find that one handful of soil has thousands of different kinds of microbes and billions of cells, which respond to the environment differently. They also determine how old the carbon is in the samples using carbon-14 dating.

“One thing we’ve seen this summer is that the carbon that is being decomposed just above the permafrost is more than 2500 years old,” described Torn. “So this place that we’re studying has been storing carbon for a long, long time. But that carbon can be decomposed and released as carbon dioxide very quickly when the conditions are right.”

These results have been validated by other recent experiments, but they contradict the old belief that carbon hidden deep in soil will remain there forever due to the soil’s material properties. “The field is evolving rapidly. We’re trying to unravel the mystery of why we see older carbon in the soil, trying to create a more realistic view,” explained Torn. “It is more complex. It’s the interaction between the entire ecosystem and the material properties that’s important.”

Of course the more complicated, realistic view makes climate modeling more challenging. Climate models are computer programs that simulate how the climate has changed in the past and how it will change in the future. They are critical to understanding our planet and how to limit the impact of human activity upon it. But scientists know that their climate models are wrong when it comes to soil carbon. This is why scientists need new data, like they are acquiring in Alaska, to test and improve their models.

“We can do so much better than we’re doing,” exclaimed Torn. “So we feel pretty confident that we can make improvements. It may not be perfect, but our work is going to make predictions more robust and believable.”

This is a repost of my KQED QUEST blog titled, “The Great Escape: How Soil Protects Us from Carbon Emissions.”

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New Portable Device Quickly Measures Radiation Exposure

September 4, 2013
Scientists are developing a portable device that can measure a person's radiation exposure in minutes using radiation-induced changes in the concentrations of certain blood proteins. This image shows a magneto-nanosensor chip reader station, chip cartridge, and chip. (Credit: S. Wang)

Scientists are developing a portable device that can measure a person’s radiation exposure in minutes. This image shows a magneto-nanosensor chip reader station, chip cartridge, and chip. (Credit: S. Wang)

Picture the scene of the Fukushima nuclear accident. The Daiichi nuclear reactors were hit by an earthquake of magnitude 9.0 and flooded by the resulting tsunami, which caused a nuclear meltdown and release of radioactive materials. Over 100,000 people were evacuated from their homes due to the threat of radiation contamination.

In a large-scale radiological incident like this, emergency medical personnel need a rapid way to assess radiation exposure so they can identify the people who need immediate care. This radiation-dosimetry technology needs to be sensitive, accurate, fast and easy to use in a non-clinical setting.

Local scientists have developed a small, portable device that can quickly test the level of radiation exposure victims have suffered in such emergencies. This technology was developed by scientists from Berkeley Lab, Stanford University and several other institutions, as reported in a journal article recently published in Scientific Reports. The lead researchers were Dr. Shan Wang from Stanford University and Dr. Andrew Wyrobek from Berkeley Lab.

This new dosimetry device is a novel type of immunoassay. Immunoassays are chemical tests used to detect or measure the quantity of a specific substance in a body fluid sample using a reaction of the immune system. For example, a common immunoassay test for pregnancy measures the concentration of the human chorionic gonadotropin hormone in a woman’s blood or urine sample.

In order to measure a person’s radiation dose, the new device measures a blood sample for the concentration of particular proteins that change after radiation exposure. Scientists, including those in Wyrobek’s group, have previously identified these target proteins as excellent biological markers for radiation dosimetry. Basically, blood exposed to radiation has a special biochemical signature.

But scientists needed more than just target proteins. They also needed an accurate, sensitive way to quickly measure the proteins’ concentrations in a few drops of blood. So at the heart of the new device is a biochip developed by Wang’s group.

The biochip system relies on a sandwich structure where a target protein is trapped between a capture antibody and a detection antibody. The capture antibodies are immobilized on the surface of the biochip sensor. When a drop of blood is placed on the biochip, those antibodies capture the target proteins and the other proteins are washed away. Detection antibodies labeled with magnetic nanoparticles are then added, forming a sandwich structure that traps the target proteins. When an external oscillating magnetic field is then applied, the magnetic nanoparticles generate an electrical signal that is read out. This signal measures the number of magnetic nanoparticles bound to the surface, and this indicates the number of target proteins that have been trapped.

The researchers tested the biochip system using blood from mice that had been exposed to varying levels of radiation. Their novel immunoassay results were validated by comparing them to conventional ELISA immunoassay measurements. Overall the scientists demonstrated that the new biochip dosimetry system is fast, accurate, sensitive and robust. In addition, the whole system is the size of a shoebox so it is very portable.

“You add a drop of blood, wait a few minutes, and get results,” explained Wyrobek in a press release. “The chip could lead to a much-needed way to quickly triage people after possible radiation exposure.” Although the technology is still under development, hopefully it will be available before the next radiological accident or terrorist attack occurs.

For more information about this biochip system, check out my KQED Science blog.


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