Rivers with changing bottom have a better capacity to save carbon

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To control the scattering of elements on the Earth, various elemental cyclic processes are carried out. In these, the importance of the carbon cycle has increased a lot nowadays. Carbon has been stored in many places and processes on Earth for thousands of years in the form of reserves. But due to human activities such as fossil fuels, this carbon reaches the atmosphere in the form of carbon dioxide in large quantities. Other harmful effects are seen along with increasing the temperature of the whole Earth. A study has found that rivers that keep changing their bed have better carbon sinks than straight flowing rivers.

Rivers are considered very important in terms of carbon storage. They have a fantastic ability to shed and scatter particles. It takes 8500 years for a sand particle present on the Andes Mountains to be washed away in the lowlands of the Rio Parana, Argentina. This 1200 km journey of the Rio Bermejo River has many blockages in the river’s floodplains, where these particles are dispersed. Sometimes they get stuck there for thousands of years. After this again washed away in the rain and reached the river.

Along with the sand flowing in the rivers, organic carbon is washed away from the plants and soil and comes with it. This transport of water becomes of great importance in terms of climate. Rivers carry carbon that was previously removed from the atmosphere through photosynthesis. It reaches the oceans in sediments from rivers where it remains stored for thousands of years without harming the climate. After this, by ocean biological processes, it is converted into carbon dioxide and reaches the air. In this way, rivers are an essential part of the carbon cycle.

Researchers from the German Research Center for Geosciences (GFZ) have measured these processes for the first time and published them in Nature Geoscience. The most important result of their work was that most of the carbon deposition or reabsorption occurs in the uninterrupted diversion areas of the rivers. After that, they go directly into the ocean. Whereas in the stretches of straight rivers, where there are permanent banks, only dormant particles move forward. In contrast, the carbon of the floodplains of such rivers is gradually converted back to carbon dioxide by microorganisms.

Dirksasche, who leads the GFZ working group, said the Rio Bermejo was the ideal natural river for this study because it has no significant tributaries. Sascha is the director of the Helmholtz program “Changing Earth – Sustaining our Future” titled Landscape of the Future. They say this means that the river’s natural course, which has erosion sites in the floodplains, has a greater capacity to remove carbon from the atmosphere than the straight river stretches.

In this sense, the straightening of rivers by humans can increase the amount of carbon dioxide in the atmosphere. Interestingly, by giving more space to the rivers or not obstructing their natural bends, we can help the climate. The study’s first author and GFZ’s Marcia Repache studied rivers and their floodplains with various instruments, one of which was an analysis of the amount of cosmogenic beryllium-10 that showed the time of the depression’s journey.

Based on the dating of the unstable carbon isotope 14C, the researchers could conclude the age of the particles of any biological origin. Samples were taken from many parts of the river while working in Argentina. Rupesh said that naturally, the meanders of rivers eroded the material of the flood plains and carried them to the sea. Where they live for a long time. At the same time, the flow of artificially fixed rivers is a less effective carbon sink.