Karst biogeochemistry in China: past, present and future

摘要

The dissolution and deposition processes of carbonate rock, called CO2-water-carbonate rock interaction, are controlled by complex interactions among the biosphere, pedosphere, atmosphere, and lithosphere. The interactions between biogenic activity and the CO2-water-carbonate rock system (dissolution and precipitation of carbonate rocks, element cycles and so forth) had been named karst biogeochemistry. In order to reveal their internal control mechanism over space and time, Chinese researchers undertook an in-depth exploration of their interrelationships. The main results of karst biogeochemistry in China can be summarized as follows: (i) biogenic activity plays an important role in regulating dissolution and precipitation of carbonate rocks; (ii) biogenic metabolic effects are involved in the positive or negative modulation of delta C-13, delta N-15 and the cycling of other elements; (iii) CO2 exchange during carbonate rock dissolution and precipitation, which is mainly due to photosynthesis, results in the accumulation of organic matter; and (iv) primary karst biogeochemistry models have been established to evaluate carbon and nitrogen cycling. In addition to these findings, future studies should increasingly focus on the following topics: (i) the apparent stability and transformation of dissolved organic carbon caused by microbial activities need to be clarified; (ii) the temporal-spatial scales of microbial biomineralization and the accompanying variances of karst biogeochemical cycles should be investigated to comprehensively understand the transformations and transport of substrates from biological activity in the CO2-water-carbonate rock system; (iii) regional-global scale models on karst biogeochemical cycles should be developed for the study of large/small-scale spatial and temporal variance on karst biogeochemical cycles; (iv) new advanced techniques and methods are required and should be applied for the karst studies involving mathematics, hydrochemistry, isotope chemistry, geology, biology and so forth.