Carbonic anhydrase activity of the water-body in different eco-environments of river basins: A case study in the Guijiang river basin

The water-bodies in six tributaries and mainstream, which have different geologic types and different degrees of human activities, are chosen as the research object during investigating the Guijiang river basin. The carbonic anhydrase (CA) activity, free CO2 and HCO3- concentration of the water-bodies under different ecological environments are compared. The data of normalized difference vegetation index (NDVI) among some areas within the river basin are also compared. The following results are obtained :( 1) It is confirmed that the water has CA activity. Its activity is negatively correlated with free CO2 concentration and positively correlated with HCO3- concentrations; (2)Large number of human activities exacerbate the deterioration of the ecological environment in the river basin and result in vegetation cover reduction, so that the CA activity and HCO3- concentration of the water-bodies in the river decreases, indicating that the influence of CA on karst carbon sinks cannot be ignored; (3)The geological type in the river basin would affect CA activity of the water-bodies. Under the condition of similar degrees of human activity, the CA activity of the water-bodies in the karst area is higher than that in the non-karst areas. In summary, to investigate the carbon sink potential in the river basin, the impacts of human activities, eco-environments and geologic types should be comprehensively considered, and scientific segment research and calculation should be conducted. Furthermore, the biological karstification induced by CA cannot be ignored, and its contribution to the carbon sink potential deserves research.