image: Four components are involved in land-water-air interface C cycle processes (DIC, DOC, POC, and CO2) at three different interfaces (the water-land interface, the water-air interface, and the sediment-water interface). This process mainly includes the following sources: river and groundwater DOC, DIC, and POC inputs; river and groundwater DOC, DIC, and POC outputs; atmospheric DIC, DOC, and POC deposition inputs; and the absorption and emission of CO2. Photosynthesis, mineralization, and flocculation are the main factors that effectuate the mutual conversion of DIC, DOC, and POC. POC is deposited in sediment, and carbon is released from sediment. Carbon flux is equal to the carbon concentration multiplied by the carbon released. view more
Credit: ©Science China Press
The study was led by Prof. Yu Guirui and Gao Yang's team from the Institute of Geographic Sciences and Natural Resources Research, CAS. This paper analyzes global land-water-gas carbon transport and carbon budget changes and their influencing mechanisms, focusing on the important role of inland water carbon budget and carbon cycle in land-sea-gas carbon budget, and reveals the regulation mechanism of land-water-gas carbon budget and carbon balance under global change. In addition, the present situation of land-water-gas carbon budget and lake carbon sequestration potential in China are further evaluated.
The land-water-air coupling process include the combined significance of the four components involved in cycling processes regarding the link between land-air exchanges and land-sea interactions (DIC, DOC, POC, and CO2) at three different interfaces (the water-land interface, the water-air interface, and the sediment-water interface). Although the conversion of CO2 from inland water systems to the atmosphere is a recognized component of the global carbon cycle, there is no usable framework to estimate global water surface area and gas exchange rates and no existing global CO2 database.
The carbon fixation process of inland water systems mainly includes the conversion of inorganic carbon into organic carbon by plants through photosynthesis, water carbon fixation, and sediment carbon fixation. The conversion process between inorganic carbon and organic carbon pools mainly includes the following: floating leaf plants and emergent plants that directly absorb atmospheric CO2, while phytoplankton use aqueous CO2 and bicarbonate in water during photosynthesis, which effectually produces gross primary productivity; phytoplankton and emergent plants release CO2 directly to the atmosphere through respiration, and phytoplankton and animal species release CO2 through respiration, which effectually generates the DIC found in inland water bodies; organic carbon can also be converted into inorganic carbon through microbial-induced degradation and mineralization of organic carbon pools.
Climate change is an important driver of riverine-based carbon transport processes, and dam construction, urban sewage discharge, dredging, waterway storage as well as other anthropogenic-derived activities have gradually become important factors that affect carbon sources, carbon cycling, and carbon budgets at the land-water-air interface.
Complexities and uncertainties related to carbon budget assessments at the land-water-air interface under global climate change make it difficult to determine how natural or anthropogenic activities will affect carbon cycling processes. Anthropogenic activities are known to affect several driving factors, such as land-water carbon flux and land-air and water-air carbon exchanges. However, it remains difficult to quantitatively analyze the effects of these anthropogenic activities on carbon flux. Understanding the precise direction and magnitude of various anthropogenic-induced impacts on land-water-air interface carbon transport and carbon exchange processes is therefore critical to balance the global carbon budget and to measure the global terrestrial carbon sink.
See the article:
Carbon budget and balance critical processes of the regional land-water-air interface: Indicating the earth system’s carbon neutrality
https://doi.org/10.1007/s11430-021-9883-3
Journal
Science China Earth Sciences