Mobilisation of Buried 'Black carbon' - Deposits flow from soil to oceans

By sampling rivers all around the world, the researchers estimated that the annual amount of black carbon flowing via rivers to the ocean is 27 million tons per year.

A smaller proportion of black carbon created during combustion will remain in soil than have been estimated before.

Contrary to previous understanding, burying black carbon in the ground to restrain climate change will not create a permanent carbon reserve.

Instead, a part of black carbon will dissolve from soil to rivers. The flux of dissolved black carbon from the rivers to the ocean was estimated in a research article published in Science.

The burning of organic matter creates 40 million tons of black carbon every year. Black carbon is formed through the incomplete combustion of organic matter, e.g. in forest fires, slash-and-burn and controlled burning of fields.

The general assumption has been that black carbon would remain in soil even for millions of years.

However, recently published research indicates that a remarkable proportion of black carbon in soil will dissolve to the water system.

In the light of new research results, much discussed "bio-carbon" may not be that beneficial in terms of mitigating climate change.

Carbon is given the prefix "bio" when it is used both for energy production and soil enrichment. In any case, the stability of carbon in soil has been a central factor of bio-carbon applications.

By sampling rivers all around the world, the researchers estimated that the annual amount of black carbon flowing via rivers to the ocean is 27 million tons per year.

"Each sample included a significant amount of black carbon," says a research participant Anssi Vahatalo  Senior Lecturer from the University of Jyvaskyla, Helsinki.

"On average, the amount of black carbon was ten per cent of the amount of dissolved organic carbon. The results prove that the proportion of water soluble black carbon may be as much as 40 per cent of black carbon created annually.

Anssi Vahatalo

Water samples from the largest rivers in the world
The basis of the research was the 'Big river'-project started by Senior Lecturer Anssi Vahatalo while he was working as an Academy Research Fellow at the University of Helsinki before moving to the University of Jyvaskyla. For this project, water samples were collected from the ten largest rivers in the world.

"These rivers carry one third of fresh water running to oceans, and their catchment area covers 28% of the whole land area in the world. Water samples were taken, e.g. from Amazon, the largest river in the world," says Vahatalo.

In addition to the samples used in the river project, the research published in Science was supplemented with samples from many other rivers all over the world. The total number of researched samples was 174.

NASA MARS Curiosity: 'Mars Flower' Photo

This photo from the Mars rover Curiosity is a close-up of a transparent rock feature that some have dubbed a "flower." 

Researchers say that its origins are not biological. 

CREDIT: NASA/JPL-Caltech/Malin Space Science Systems

An odd flower-like feature spotted on Mars by NASA's Curiosity rover continues to perplex researchers, who nevertheless stress that its origins are not biological.

The object garnered a lot of attention after Curiosity photographed it last month, with many Internet users quickly dubbing it the "Mars flower."

The feature is actually a rounded, light-colored pebble slightly larger than a grain of sand, but determining its precise mineralogical makeup would require more information, researchers said.

"It could be a lot of things, but without some chemical information to back me up, I'd really hesitate to say what it is," Aileen Yingst, of the Planetary Science Institute in Tucson, Ariz., told reporters today (Jan. 15).

"I'm not trying to be cagey," added Yingst, the deputy principal investigator for Curiosity's Mars Hand Lens Imager, or MAHLI. "I'm just trying to be clear that a light grain could be a lot of different things."



The so-called Mars flower juts from a rock near an outcrop mission scientists have named "John Klein," in honor of a former Curiosity deputy project manager who died in 2011.

The car-size rover is preparing to use its drill for the first time in the area, boring into a John Klein rock over the next two weeks or so.

The outcrop and its environs show many signs of long-ago exposure to liquid water, including water-deposited mineral veins that fill fissures in the rock. John Klein is thus a suitable drilling target for Curiosity, whose main goal is to determine if Mars has ever been capable of supporting microbial life.

The Mars flower is not a sign of life, but it does add to the site's intrigue, researchers said.

"It does indicate that you have, you know, a relatively diverse set of grains just in this one sample," Yingst said.