湖泊沉积有机碳埋藏效率及其影响要素研究进展

Progress of research on the burial efficiency of organic carbon and its influencing factors in lacustrine sediments

湖泊是地球上重要的碳库之一,湖泊有机碳埋藏效率决定湖泊碳源-汇的转换关系,因而在湖泊碳及全球碳循环中的作用越来越受到人们的重视。本文综述了物理、化学、生物及人类活动对湖泊碳埋藏效率的影响,并探讨了湖泊碳储量和碳循环对湖泊碳埋藏效率变化的响应。目前湖泊有机碳埋藏效率的研究还存在区域研究有限、影响因子少等问题,缺乏系统性,多限于观测,对机制机理的理解比较薄弱。今后的研究可以从以下几个方面加强:(1)不同区域不同环境条件下碳埋藏效率的差异性研究;(2)在全球气候变暖大背景下,探讨碳埋藏效率对增温的响应及碳埋藏效率发生变化后如何反馈于气候变化;(3)定量分析碳埋藏效率的整个地球、物理、化学和生物过程,建立相关的模型。

Background, aim, and scope Lake ecosystem is one of the most significant carbon pools on the earth. In recent years, burial carbon efficiency of lakes plays a key role in global carbon cycle, which has been paid more and more attention. In this paper, we summarized the physical, chemical, biological, and anthropogenic factors that affect buried carbon efficiency of lakes. Accordingly, we explored carbon stock and carbon cycle of lakes in response to the burial efficiency of organic carbon. Materials and methods A comparative study of the carbon burial efficiency in lacustrine sediments from different regions of the world has been conducted in the collection, screening and sorting of published literatures, covering a number of research cases and obtaining the conclusions of series. Results The results show that the impact on organic carbon burial efficiency mainly includes the following aspects. The effect of atmospheric temperature on lake organic carbon burial efficiency varies with time and place. It is now widely accepted that as the temperature of the atmosphere increases, the decomposition rate of organic carbon is accelerated and the release of CO2 from the lake to the atmosphere increases. However, There are regional differences that the regularity of the organic carbon mineralization rate increases with increasing temperature. The variation of precipitation variability and intensity, the climate areas such as humid areas and arid and semi-arid areas have noticeable effects on the organic carbon storage of lacustrine sediments. As the variability and intensity of precipitation increase, organic carbon dissolved from land to aquatic ecosystems will increase. Compared with lakes in wet areas of eastern China, especially shallow lakes, the amount of organic carbon in lakes is much larger in arid and semiarid regions. The physical and chemical factors influencing the organic carbon burial efficiency of lakes mainly include lake water type, organic carbon source and content, oxygen penetration depth, dissolved oxygen concentration in bottom water, oxygen exposure time and lake nutrient status. The carbon burial efficiency of lacustrine is affected by the organic carbon source. In many lakes, the respiration from the input of dissolved organic carbon （DOC） is stronger than that from the buffed organic carbon in the lake. Relatively short oxygen exposure times and high levels of terrestrial organic matter contribute to organic carbon burial, while relatively long oxygen exposure times and low levels of endogenous organic matter accelerate mineralization of organic matter and thus hinder organic carbon burial. On the one hand, the burial efficiency of organic carbon is related to the depth of dissolved oxygen and oxygen, and the less oxygen in the bottom water is, the more favorable is the storage of organic carbon, the higher the organic carbon burial efficiency, the organic carbon burial efficiency and the organic matter source and sediment oxygen exposure time is closely related to the exposure time with the increase in a linear downward trend. Biological factors on the organic carbon burial efficiency mainly include types of organisms in the lake, lake basins within the vegetation coverage. As the biomass of lake increases, the organic matter content of photosynthesis increases, and the deposition rate of organic carbon in lakes will be accelerated. However, organic carbon will be decomposed and mineralized by microbe during in the process of deposition. The burial efficiency of organic carbon is not necessarily increased. Human activities include land use change, non-point pollution of farmland in lake basins, intensive agricultural development, the development of tourism in the surrounding area of lakes, the rise of urbanization. All human activities carried out in the lake and its catchment areas due to human needs have implications for the burial of organic carbon in lakes. The change of land use patterns has been considered as one of the most important human activities. Discussion The organic carbon in lacustrine is related to the research of physics, chemistry and biology. It belongs to the popular component of climate change, and there is a close relation among them. Among the many influencing factors, climatic factors have significantly influence on the organic carbon sequestration efficiency of lacustrine sediments. The impact of human activities on the organic carbon burial of lakes is becoming more and more increasingly, and the ways of impacts are diversified. With the urbanization of lakes and the rise of tourism, the change of land use pattern has a dramatically impact on the organic carbon burial of lakes. Conclusions In this paper, the factors influencing the organic carbon burial efficiency of lakes are reviewed, which is of great significance to the study of lake carbon cycle and its role in global climate change. Nevertheless, the extent of the impact of how much, the specific impact of the process mechanism and what kind of human action should be taken are not further investigated. Recommendations and perspectives There have been problems with limited regional, seldom impact factors, and with lacking of systematically, more limited to observation, and the understanding of mechanism in the study of burial efficiency of organic carbon. Further research can be strengthened from the following several aspects： （1） Carbon burial efficiency of different research should be carried out under different environmental conditions and regions. （2） Under the background of global warming, exploring carbon burial efficiency in response to warming and how its variation feedback to the climate change. （3） Quantitative analysis of buried carbon efficiency of the whole earth＇s physical and chemical biological process should be carried out, to establish relevant models. （4） How is the impact of human activities on the organic carbon burial effects of lakes？ Can human beings take appropriate measures to sequester and store carbon emissions from human activities, depending on the size of carbon burial？