Study on carbon sink effect in typical sub-tropical karst water system

Three karst water systems in South China with different geological conditions and eco-environment are selected to study the differences of the dissolved inorganic carbon and carbon sink effect. These karst water systems include Guancun underground river system in shrubbery and distinct human impact area, Mumei underground river in rock desert and Banzhai underground river in primeval forest. The results of the study prove that: (1) concentration of dissolved inorganic carbon in different locations and seasons is the highest in Guancun, Mumei the second and Banzhai the lowest; (2) the PCO2 pressure in those three studied underground river waters tend to be saturated, with Mumei the biggest, Guancun the second and Banzhai smallest; (3) the quantity of karst carbon sink in Guancun, Banzhai and Mumei is 12.34 tC/(km2.a), 11.8 tC/(km2.a) and 34.11 tC/(km2.a) respectively. Rock desertification area covered 90% of the total area in Mumei, showing a serious ecosystem environment, while Banzhai is primeval forest. Large drainage area, strong regulation and storage capacity and allogenic water contribute to high carbon sink in Mumei underground river system. Therefore the potential carbon sink in karst water systems can not be explained only in view of eco-environment.