With global warming and permafrost degradation, the large amount of dissolved organic carbon (DOC) stored in the permafrost zone is becoming more susceptible to decomposition and transport. DOC decomposition will release greenhouse gases to the atmosphere and aggravate global warming. However, there is currently little understanding of how the content and degradability of DOC in soil waters of peatlands in permafrost regions vary? and the influencing factors that determine DOC degradation are not clear. Here, we measured concentrations of DOC under dark control and light-exposed experiments for surface water in peatland area in different seasons and the biodegradability of DOC in autumn. The loss of DOC caused by sunlight is different in spring, summer and autumn. The loss of DOC in spring is the most, followed by summer and the least in autumn, and the DOC produced during thawing in spring has higher photoreactivity. Compared with dark treatment, all the samples exposed to sunlight have lower DOC. In the study of DOC biodegradation, the DOC in soil at different depths gradually decreased under the action of microbial decomposition. The loss rate of biodegradable dissolved organic carbon (BDOC) in soil water at different depths was 14.04-31.61%, and the BDOC in surface water was significantly higher than that in other soil layers. During the incubation, the cumulative amount of CO₂ emission from dissolved water in frozen soil layer was significantly higher than that in other soil layers. These results demonstrate that DOC in peatland has high photodegradation and biodegradability, which highlights its crucial role in global carbon cycle under climate change.
 

permafrost peatland,dissolved organic carbon,DOC photodegradation,biodegradability