Monday, April 22, 2013

Black carbon flows

Black carbon rears its head again! This time it breaks earlier notions of creating a carbon reserve in soil.

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 in order to restrain climate change will not create a permanent carbon reserve. Instead, a part of black carbon will dissolve from soil to rivers.

The burning of organic matter creates 40-250 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. In the light of new research results, much discussed "bio-carbon" may not be that beneficial in terms of mitigating climate change. 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. 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. 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.

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