July 8, 2014
Wildfires Found To Release A Previously Unidentified Type Of Soot
Alan McStravick for redOrbit.com - Your Universe online
Globally, wildfires are responsible for creating veritable ecological wastelands across millions of hectares of land each year. As the effects of climate change have become ever more pronounced over the previous years, we have seen both the number and severity of wildfires increase drastically.
Another dangerous by-product of the fires is the massive amount of soot that careens skyward from the flames. It is estimated wildfires are responsible for 34 percent of global soot mass into the atmosphere. In some areas, such as Southeast Asia and Russia, fires can actually be expected to contribute upwards of 63 percent of regional soot mass.
A new study authored and led by Rajan Chakrabarty from Nevada's Desert Research Institute has, for the first time, observed a previously unrecognized form of soot particle which the research team has identified as a “superaggregate,” from wildfire emissions. The paper, recently published in Nature's journal Scientific Reports, claims this new soot particle has been detected in smoke plumes from wildfires in Northern California, New Mexico, Mexico City and India.
One of the reasons this study is both interesting and important is that scientists have, for several decades, been trying to quantitatively assess the impacts on climate change and human health as a result of wildfire soot. Hampering previous study was the unpredictability of wildfire occurrences paired with the extreme difficulty in being able to sample a smoke plume in real-time.
The team noted the structural differences between common soot particles, like those emitted from cook stoves and vehicle tailpipes, and superaggregates. The newly discovered soot particle is, on average, 10 times longer while also having a more compact shape than its more familiar cousin. Despite the greater length, superaggregates have low effective densities. This, according to the study team, allows the wildfire-emitted soot to travel over long distances and more easily invade a human lung.
"Our observations suggest that we cannot simply assume a universal form of soot to be emitted from all combustion sources. Large-scale combustion sources, such as wildfires, emit a different form of soot than say, a small-scale, controlled combustion source, such as vehicles." says Chakrabarty, who also holds a faculty appointment at Washington University in St. Louis.
Chakrabarty believes this study should be the first step in revisiting and reclassifying the soot formation mechanism in wildfires.
First becoming aware of the presence of superaggregates while studying the 2012 Nagarhole National Forest fire in western India, the team wanted to verify the presence of these same particles in other fires around the globe. This led them to analyze smoke samples that were collected from the 2010 Millerton Lake fire in Northern California as well as the Las Conchas fire in New Mexico which occurred in 2011. These three fires, as well as other fires in and around Mexico City, showed that a large portion of soot emitted during the flaming phase of these fires were superaggregates.
Now that the team had determined the existence of this new soot particle, the next step was to attempt to assess the potential impact it could have on global climate. To do this, the team calculated the radiative properties of soot superaggregates using numerically-exact electromagnetic theory.
"We found that superaggregates contribute up to 90 percent more warming than spherical sub-micrometer soot particles, which current climate models use," said Chakrabarty. "These preliminary findings warrant further research to quantify the significant impact these particles may have on climate, human health, and air pollution around the world."
These findings are especially salient in light of research presented earlier this year by scientists from Yale University who claimed particulate matter and smoke put off from wildfires during the Pliocene epoch effectively swung the radiation balance of the Earth resulting in an exceptionally hot era for the planet.
“The discovery is important for better understanding climate change throughout Earth’s history, and has enormous implications for the impacts of deforestation and the role of forests in climate protection strategies,” said Nadine Unger, an assistant professor of atmospheric chemistry at Yale.
Some scientists believe that the Pliocene epoch is not only a snapshot of Earth’s past, but could be an example of Earth’s future.
“We might do a lot of work to reduce air pollution from road vehicle and industrial emissions, but in a warmer future world the natural ecosystems are just going to bring the ozone and aerosol particles right back,” Unger said. “Reducing and preventing the accumulation of fossil-fuel CO2 is the only way to ensure a safe climate future now.”
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