Nav: Home

Charcoal: Major missing piece in the global carbon cycle

July 09, 2018

Most of the carbon resulting from wildfires and fossil fuel combustion is rapidly released into the atmosphere as carbon dioxide. Researchers at the University of Zurich have now shown that the leftover residue, so-called black carbon, can age for millennia on land and in rivers en route to the ocean, and thus constitutes a major long-term reservoir of organic carbon. The study adds a major missing piece to the puzzle of understanding the global carbon cycle.

Due to its widespread occurrence and tendency to linger in the environment, black carbon may be one of the keys in predicting and mitigating global climate change. In wildfires, typically one third of the burned organic carbon is retained as black carbon residues rather than emitted as greenhouse gases. Initially, black carbon remains stored in the soil and in lakes, and is then eroded from river banks and transported to the ocean. However, black carbon is not taken into account in global carbon budget warming simulations, because its role in the global carbon cycle is not well understood as a result of a lack of knowledge about fluxes, stocks, and residence times in the environment.

First worldwide assessment of black carbon river transport

"Our study is the first to address the flux of black carbon in sediments by rivers on a global scale. We found that a surprisingly large amount of black carbon is exported by rivers," says lead author Alysha Coppola, a postdoctoral researcher in the Department of Geography at the University of Zurich (UZH). The study includes some of the largest rivers worldwide, such as the Amazon, Congo, Brahmaputra, and major Arctic rivers. It is the first global river assessment of the radiocarbon age values and amount of black carbon transported as particles. The researchers found that the more total river sediment is transported by rivers to the coast, the more black carbon travels with it and is ultimately buried in ocean sediments, forming an important long-term sink for atmospheric carbon dioxide.

Black carbon can age in intermediate reservoirs

To gain an overview of the processes occurring in the world's rivers, the UZH researchers teamed up with colleagues from ETH Zurich, and the US-based Global Rivers Observatory at the Woods Hole Oceanographic Institution and the Woods Hole Research Center. They discovered that the black carbon pathway from land to ocean is mainly shaped by erosion in river drainage basins. Surprisingly, they found that some black carbon can be stored for thousands of years before being exported to the ocean via rivers. This insight is new, since it was previously always assumed that after a fire, the remaining black carbon was quickly eroded by wind and water.

However, the authors found that black carbon does not always originate from recent wildfires, but could be up to 17,000 years old, particularly in the Arctic. "This explains the mystery as to why black carbon is continuously present in river waters, regardless of wildfire history. We found that black carbon can age in intermediate reservoirs that act as holding pools before being exported to the ocean," says Alysha Coppola.
-end-
Literature:

Alysha I. Coppola, et. al. Global scale evidence for the refractory nature of riverine black carbon. Nature Geoscience. July 9, 2018. DOI: 10.1038/s41561-018-0159-8

University of Zurich

Related Wildfires Articles:

Fire blankets can protect buildings from wildfires
Wrapping a building in a fire-protective blanket is a viable way of protecting it against wildfires, finds the first study to scientifically assess this method of defense.
Stanford researchers have developed a gel-like fluid to prevent wildfires
Scientists and engineers worked with state and local agencies to develop and test a long-lasting, environmentally benign fire-retarding material.
UCI team uses machine learning to help tell which wildfires will burn out of control
An interdisciplinary team of scientists at the University of California, Irvine has developed a new technique for predicting the final size of a wildfire from the moment of ignition.
New wildfire models to predict how wildfires will burn in next 20 minutes
While it's impossible to predict just where the next wildfire will start, new Department of Defense-sponsored research from BYU's Fire Research Lab is getting into the microscopic details of how fires initiate to provide more insight into how wildfires burn through wildland fuels.
Tiny airborne particles from wildfires have climate change implications
Wildfires are widespread across the globe. They occur in places wherever plants are abundant -- such as the raging fires currently burning in the Brazilian Amazon.
How California wildfires can impact water availability
A new study by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) uses a numerical model of an important watershed in California to shed light on how wildfires can affect large-scale hydrological processes, such as stream flow, groundwater levels, and snowpack and snowmelt.
Wildfires could permanently alter Alaska's forest composition
A team of researchers led by Lawrence Berkeley National Laboratory projected that the combination of climate change and increased wildfires will cause the iconic evergreen conifer trees of Alaska to get pushed out in favor of broadleaf deciduous trees, which shed their leaves seasonally.
How wildfires trap carbon for centuries to millennia
Charcoal produced by wildfires could trap carbon for hundreds of years and help mitigate climate change, according to new research.
A drier future sets the stage for more wildfires
November 8, 2018 was a dry day in Butte County, California.
Geography study finds hot days lead to wildfires
University of Cincinnati geography researchers found that temperature was a better predictor of wildfire than humidity, rainfall, moisture content of the vegetation and soil and other weather factors.
More Wildfires News and Wildfires Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#544 Prosperity Without Growth
The societies we live in are organised around growth, objects, and driving forward a constantly expanding economy as benchmarks of success and prosperity. But this growing consumption at all costs is at odds with our understanding of what our planet can support. How do we lower the environmental impact of economic activity? How do we redefine success and prosperity separate from GDP, which politicians and governments have focused on for decades? We speak with ecological economist Tim Jackson, Professor of Sustainable Development at the University of Surrey, Director of the Centre for the Understanding of Sustainable Propserity, and author of...
Now Playing: Radiolab

An Announcement from Radiolab