The river brought a third black carbon from forest fires into the ocean

Every year rivers bring into the ocean more than 30 percent of black carbon — a byproduct of incomplete combustion of biomass in wildfires. In the ocean, this carbon is derived from biological circulation in the thousands and even tens of thousands of years, undermining the sustainability of the prevailing biogeochemical cycle of carbon. The authors of an article published in the journal Nature Communications, believe that the cause of this dangerous trend is the rise of wildfires in the subtropical latitudes and the Arctic.

As a result of natural fires formed an important by-product of incomplete combustion of organic matter — the so-called black carbon. It is practically not available for processing by microorganisms because of their polycondensating aromatic molecular structure. Each year, through incomplete combustion of biomass produces about 40-215 million tons of black carbon, and from 2 to 29 million tons are the result of emissions of black carbon (as a result of natural fires and anthropogenic burning of fossil fuels). About 80 percent of this mass is in tropical forests and savannas.

A large part of black carbon is preserved in the soil, where it is subjected to microbial mineralization over a several hundred — several thousand years. However, part of the black carbon falls into the river, where it becomes either dissolved organic matter (dissolved organic carbon, DOC) or particulate organic matter (particulate organic carbon, POC). The residence time of black carbon in ocean basins is far superior to its conservation in the soil and is thousands and even tens of thousands of years. For so long the removal of carbon from the biological cycle can disrupt planetary biogeochemical cycles of carbon, if the loss of the black carbon will increase as a result of increased wildfires.

Scientists led by Matthew Jones (Matthew W. Jones) from the University of East Anglia investigated the transfer of black carbon in the World ocean with the river runoff. For this, they used data of 17 scientific publications, including measurement of black carbon in 409 points across the planet, and evaluation of migration mobility.

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