多年冻土退化下碳、氮和污染物循环研究进展

Cycling of carbon,nitrogen and pollutants under permafrost degradation:a review

多年冻土储存了大量的有机碳、氮素以及持久性有机污染物和汞等污染物。全球变暖背景下,目前全球大部分的多年冻土都处于退化状态。多年冻土区土壤温度升高、多年冻土层解冻后,土壤温度水分会发生变化,从而改变微生物的生长代谢过程,进而改变多年冻土区的物质循环。通过综述多年冻土区的碳、氮及污染物的储量及其在多年冻土退化下的迁移转化及输出特征,研究发现:多年冻土退化增加活动层厚度、形成热喀斯特地貌,一方面导致碳基和氮基温室气体快速释放到大气中,另一方面也向水生系统中输出溶解性碳氮组分及可溶性污染物,这些过程会导致多年冻土由碳、氮和污染物储存的“汇”转变为“源”,并最终影响全球生物地球化学循环。明确多年冻土区碳、氮和污染物的生物地球化学循环过程对于全面理解气候变化对自然和人类社会系统的影响具有重要作用。未来研究中,还需要结合多学科技术手段,开展多年冻土退化过程、水文过程与生物化学循环过程的系统集成研究,此外,还需加强汞、POPs等污染物的二次释放过程与碳氮循环的耦合关系研究,定量多年冻土中污染物二次释放的环境效应,以深刻认识多年冻土中物质循环过程并为气候和环境变化提供预测依据。

Permafrost degradation has been widely recorded.As the ground temperature increase and permafrost thaw,soil temperature and water content changes accordingly.These changes can greatly affect soil microbes and further exert strong effects on materials cycling in permafrost regions.Here,we summarize the storage of soil organic carbon,nitrogen,POPs and mercury in high-latitude and high-altitude permafrost regions,as well as the migration,transformation and loss of these substances.We found that active layer increase and thermo⁃karst terrain development promotes the release of carbon-based and nitrogen-based greenhouse gases.Mean⁃while,permafrost degradation also increases the lateral export of dissolved carbon,nitrogen,and pollutants.As a result,permafrost regions may shift from sink to source for these materials,and further affect their global cy⁃cles.It is of great importance to clarify the biogeochemical cycles of carbon,nitrogen and pollutants in perma⁃frost regions to fully understand the impact of climate change on ecological and social systems.In the future stud⁃ies,it is necessary to strengthen the investigation of permafrost degradation,hydrology and biogeochemistry in permafrost regions.In addition,it is also necessary to conduct the study of the relationship between the second⁃ary release of pollutants and the carbon and nitrogen cycle for provide a scientific basis for climate and environ⁃mental changes.