Southeast Asian River CO2 Outgassing Regulated by Water pH.

Inland waters and especially rivers which exist at the transition between the terrestrial biosphere, the ocean and the atmosphere are an integral part of the global carbon cycle. Southeast Asia has been recognized as a hotspot for river carbon dioxide (CO₂) outgassing because of large peatland areas in this region. These peatlands represent a globally important carbon store that is destabilized by deforestation and drainage. Despite the fact that peatland degradation is assumed to have increased carbon leaching from peat soils by about 200%, recent estimates suggest only moderate CO₂ emissions from Southeast Asian rivers. We investigated the cause for the limited emissions and found that water pH, which decreases along with increasing dissolved organic carbon concentrations, hampers respiration processes. However, high concentrations of carbonate, e.g. derived from rock weathering or soil erosion upstream of the coastal peatlands can suspend these natural limits due to its buffering impacts on pH.