It takes about 8500 years for a grain of sand from the Andes to be washed across the Argentine lowlands into the Río Paraná.
It takes about 8500 years for a grain of sand from the Andes to be washed across the Argentine lowlands into the Río Paraná. The 1200-kilometer journey in the river called Río Bermejo is interrupted by many stops in river floodplains, where the grain is deposited, sometimes over thousands of years, and then washed free again. The sand is accompanied by organic carbon, washed in from soil and plants. The transport in water thus gains relevance for the climate: Rivers carry the carbon, which was previously removed from the atmosphere via photosynthesis, as sediment into the sea, where it is stored for thousands of years without harming the climate.
Researchers at the GFZ German Research Centre for Geosciences have now quantified the individual processes of the journey for the first time and report on them in the journal Nature Geoscience. An important result of the work: It is in particular undisturbed meandering sections of a river where carbon is deposited and reabsorbed, and then transported further into the sea. In river sections with straight, stable banks, on the other hand, only the suspended particle load passes through, while the carbon in the river floodplains is slowly decomposed again to CO2 by microorganisms. GFZ working group leader Dirk Sachse says, "The Río Bermejo was an ideal natural laboratory for us because it has no significant tributaries." Sachse is also director of the "Landscapes of the Future" topic in the Helmholtz program "Changing Earth – Sustaining Our Future." He says, "This means that natural river courses that have space to erode floodplains can remove more carbon from the atmosphere than straight river sections. In this respect, straightening of rivers by humans could also contribute to the increase in atmospheric CO2 concentration. What's exciting now is answering the question of whether we can help the climate by giving rivers more space again and not impeding natural river meandering."
Read more at GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Photo Credit: smarkov2 via Pixabay
