T278 Critical Zone Science in Karst and Carbonate Terrains

Wednesday, 7 November 2018
1:30 PM - 5:30 PM
Room 130-131

THE CARBON CYCLE INDUCING BY CARBONATE ROCK WEATHERING IN A KARST CRITICAL ZONE--AN CASE STUDY IN ZHUJIANG RIVER BASIN, SOUTH CHINA

Paper number: T278-3
Program: Technical Sessions
Time: 2:10 PM – 2:30 PM

Authors

  • Jianhua Cao Presenting Author
    Institute of Karst Geology,CAGS, Guilin
  • Hui Yang
    Institute of Karst Geology,CAGS, Guilin

Abstract

In a watershed, the carbon cycle induced by carbonate rock weathering mainly consists of three parts: carbonate rocks dissolution removing the atmospheric/ soil CO2 to water and to produce inorganic carbon; inorganic carbon transfer and conversion along with water flow; inter-conversion between inorganic carbon and organic carbon with the aquatic plants photosynthesis, part of the organic carbon deposit on the river/lake/reservoir beds mixing with sediments. Zhujiang river is a typical karst watershed with the 36.32% karst cover. The investigation results show: (1) The results of soil carbon cycle in karst area in Maocun, Guilin, revealed that the weathering and dissolution of carbonate rocks under the soil resulted in a lower soil respiration of 25% than that in non-karst area(sandstone and shale), it indicates the karst carbon cycle happening. (2) The comparison on carbon exchange and isotopes at the water-gas interface between the granite and carbonate rock basins in the Lijiang River, found that the CO2 emission of the karst water is 10.92 times that of the allogenic water from non-karst area, while the carbon isotope of HCO3- in karst water is lighter by 8.62‰, it means inorganic carbon contained in karst water body dominantly from soil source and a greater karst carbon sink effect. (3) the CO2 concentration of cave air of Panlong cave in Guilin, the minimum is 300-500ppmv with heavy δ13C from Oct. to April next year, and maximum is 1000-1500ppmv with light δ13C from May to Sept. (4) When the karst subterranean stream in Zhaidi, Guilin, is exposed to surface, karst water with carbon-rich stimulated the growth of aquatic plants, and the calculation indicated that 12.52% of inorganic carbon is converted into organic carbon along the 512-meter water flow. (5) With the investigation and monitoring, the estimation of carbon source and carbon sink inducing by carbonate rock weathering in Zhujiang river has made, the total carbon flux by the carbonate rocks weathering is 1167×104 tCO2/a(100%), of them, 177.83×104 tCO2/a(15%) emitted from water to air, 46.6×104 tCO2/a(5%) deposited on the river bed, 623×104 tCO2/a(53%) inorganic carbon and 320.8×104 tCO2/a( 27%)organic carbon entered sea.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-317532

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