Effects of photodegradation on carbon components of different land use types in typical fault subsidence lakes: taking xingyun lake as an example

The burial of organic matter in the fault-sinked lakes on the plateau is an important aspect of the global cycle. Among them, terrestrial sources are a major source of dissolved organic matter (DOM) in the aquatic environment. The fault-sinked area of the plateau receives strong ultraviolet radiation on the one hand, and is also impacted by the convergence of fault geological structures on the other hand. Therefore, the photodegradation of DOM in the soil structure near the plateau faulted lake is of great significance to the carbon cycle in the natural environment. The composition and composition of DOM photodegraded into terrestrial DOM were studied. It provides a theoretical basis for the rapid photodegradation process of the structure. The simulated ultraviolet radiation photodegradation technology was used to study the changes of dissolved carbon (DC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in three types of land near wetland, forest and farmland near Xingyun Lake in the plateau faulted lake. The DOM was characterized by ultraviolet spectroscopy and infrared spectroscopy. The degree of organic carbon decomposition in different soils was strongest in wetlands, followed by forests and weakest in farmlands. The photodegradation rate of DOC increased with the increase of light intensity and duration, and the strongest photodegradation rate was found in wetlands. DIC also showed a fluctuating increase. After photodegradation, the DOM UV spectra S275--295 and S-R of all three soils will keep increasing and a350 keeps decreasing. The study showed that: a) The degradable carbon in DOC. It is the content of CDOM that is an important influencing factor in measuring the strength of photodegradation, with wetlands having the strongest photodegradation rate, followed by forests, and farmlands the weakest. b) DOM from wetland sources is characterized by strong aromaticity and high humification of large molecular weight compounds, which results in wetlands being more susceptible to photochemical degradation than DOM from farmland and forest sources. c) DIC can also be one of the effective indicators for determining the changes in DOM composition and molecular size during photobleaching.