Characteristics of soil profile CO 2 concentrations in karst areas and their significance for global carbon cycles and climate change

Chen, Qiao

inline-formulaCO2 concentrations of 21 soil profiles were measured in Zhaotong City, Yunnan Province. The varying characteristics of soil profile inline-formulaCO2 concentrations are distinguishable between carbonate and noncarbonate areas. In noncarbonate areas, soil profile inline-formulaCO2 concentrations increase and show significant positive correlations with soil depth. In carbonate areas, however, deep-soil inline-formulaCO2 concentrations decrease and have no significant correlations with soil depth. Soil organic carbon is negatively correlated with soil inline-formulaCO2 concentrations in noncarbonate areas. In carbonate areas, such relationships are not clear. This means that the special geological process in carbonate areas – carbonate corrosion – absorbs part of the deep-soil-profile inline-formulaCO2. Isotope and soil pH data also support such a process.

A mathematical model simulating soil profile inline-formulaCO2 concentration was proposed. In noncarbonate areas, the measured and the simulated values are almost equal, while the measured inline-formulaCO2 concentrations of deep soils are less than the simulated in carbonate areas. Such results also indicate the occurrence of carbonate corrosion and the consuming of deep-soil inline-formulaCO2 in carbonate areas. The decreased inline-formulaCO2 concentration was roughly evaluated based on stratigraphic unit and farming activities. Soil pH and the purity of inline-formulaCaCO3 in carbonate bedrock deeply affect the corrosion. The corrosion in carbonate areas decreases deep-soil inline-formulaCO2 greatly (accounting for 5.2 %–66.3 % with average of 36 %) and naturally affects the soil inline-formulaCO2 released into the atmosphere. Knowledge of this process is important for karst carbon cycles and global climate changes and it may be a part of the “missing carbon sink”.

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Chen, Qiao: Characteristics of soil profile CO2 concentrations in karst areas and their significance for global carbon cycles and climate change. 2019. Copernicus Publications.

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