Research progress on land-based aquatic photosynthesis carbon sequestration in geochemistry
How to accurately and effectively assess the atmospheric carbon budget has long been regarded as one of the major challenges in the global carbon cycle. One important scientific question that needs to be answered is the distribution, size and change of carbon sources and sinks in the region and even in the world. For the time being, the known carbon sources and sinks have not yet reached equilibrium, and there is still a considerable amount of “lost carbon sinksâ€. Although a large proportion of carbon sinks are thought to be found in terrestrial ecosystems, their exact size and magnitude are still controversial.
In order to answer the possible whereabouts of carbon sequestration, Liu Zaihua, a researcher at the Institute of Geochemistry of the Chinese Academy of Sciences, proposed a new model of carbonate weathering carbon cycling based on the water-rock-atmosphere-biomass interaction on the basis of the study of the traditional rock weathering carbon cycle. It is believed that this carbon cycle process is the result of coupling and interaction between water, carbonate rocks, CO2 gas, and aquatic photosynthetic organisms. It also emphasizes the important role played by terrestrial aquatic photosynthesis, which is global The whereabouts of lost carbon sinks in the carbon cycle provide a new possibility. However, at present, the organic carbon fixation in this model, namely the use of dissolved inorganic carbon by terrestrial aquatic photosynthetic organisms, the comprehensive study of the interplay between physical, chemical and biological processes and corresponding control mechanisms is still lacking. Therefore, the development of related research is of great significance.
To this end, Liu Zaihua's karst carbon cycle research team conducted a series of field experiments. They conducted high-resolution day-night observations and comparative studies of different seasons on the water chemistry dynamics of surface karst springs in the Maolin Nature Reserve in southwestern China and their downstream water systems, and the CO2 exchange at the water-gas interface: whether in the summer, In autumn and winter, the water chemistry parameters in the middle reaches of the lake all show a significant diurnal change, with DO, pH, and SIC being lower during the day and higher at night, while EC, [HCO3-], [Ca2+], and pCO2 are during the daytime. Low night high.
At the same time, there is a significant bio-carbon pump effect in the middle pool at noon and evening when there is sufficient sunlight, which is reflected by the reverse CO2 flux (CO2 enters the pool water from the atmosphere). This is mainly caused by the metabolic processes of a large number of submerged plants in the middle reaches of the lake (daytime photosynthesis is dominant, and night respiration is dominant). In contrast, the diurnal variations of water chemistry parameters were not significant in the Quankou and downstream pools. This is due to the fact that there are fewer submerged plants in the mouth of the pool and downstream pools. According to the principle of conservation of mass, the calculated carbon sink fluxes due to the effect of bio-carbon pump in the middle of autumn and winter can reach 892±300 t C km-2 yr-1 and 285±193 t C km-2 yr-1 respectively. , equivalent to 43 to 135 times that of marine bio-carbon pumps. The results of this study indicate that photosynthesis of terrestrial aquatic organisms can use and fix dissolved inorganic carbon in water, resulting in a large amount of carbonate weathering carbon sinks, which has important implications for the correct evaluation of rock weathering carbon sinks.
International peer reviewers believe that the study has systematically discussed the mechanism of terrestrial aquatic photosynthetic carbon fixation and its flux, and has important implications for the further study of rock weathering carbon cycle.
Relevant research results were published in the Journal of Hydrology, an international journal of hydrology, and Applied Geochemistry, a journal of geochemistry.
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