【作者】 吕昌伟；

【导师】 何江；

【作者基本信息】 内蒙古大学 ， 生态学， 2008， 博士

【摘要】 湖泊碳循环是陆地生态系统碳循环的重要组成部分。湖泊是地球表层系统各圈层相互作用的联结点，它以高分辨率沉积物敏感地记录着区域气候环境的变化历史。C、N、P、Si等生源要素在湖泊水-沉积物界面及其附近发生剧烈的生物地球化学循环，并控制C、N、P、Si等在上覆水体和沉积物间的物质平衡、形态转化和沉积剖面分布。湖泊水-沉积物界面的碳通量和碳过程及其变化直接影响沉积物的碳源汇功能。沉积物是全球碳的重要源与汇，在全球碳循环中扮演重要角色。碳形态及其变化对湖泊水-沉积物界面的碳通量及碳过程起关键控制作用，沉积物中碳形态是探讨碳循环的重要基础和前提。内蒙古高原湖泊湿地资源丰富，类型多样，在我国湖泊湿地的整体研究中占有重要位置。在内蒙古高原西部湖泊中，以乌梁素海和岱海的富营养化类型及湖水盐度的差异性最为明显，是探讨富营养化类型和水平对湖泊水-沉积物界面碳通量和碳过程及碳的源／汇功能等影响机制的典型区域。然而，有关该区湖泊湿地生态系统碳循环的研究迄今尚属空白。本文以碳形态研究为基础，以湖泊水-沉积物界面碳通量和碳过程的影响机制研究为主线，深入探讨了2个不同类型湖泊水-沉积物系统中碳形态分布的差异性，阐释了无机碳形态对2个湖泊生态系统碳循环的贡献，判识了2个湖泊沉积物的碳源／汇功能，取得了如下主要成果和进展。1．开展了内蒙古高原西部湖泊水-沉积物界面DIC交换通量的模拟实验研究，判识了浅水草型和深水藻型等2个不同类型湖泊沉积物的碳源汇功能。该项研究成果对评价内蒙古高原西部干旱半干旱地区湖泊沉积物的碳源汇功能和强度，厘定内蒙古高原西部湖泊碳的时空分布格局等具有重要意义。2．发现了恢复湖泊古环境古气候新的有效代用指标，拓展了古环境古气候恢复研究的方法和思路，利用陆源有机碳和形态无机碳成功恢复与重建了浅水草型和深水藻型等2个不同类型湖泊的古环境古气候。3．对比总结了浅水草型和深水藻型等2个不同类型湖泊沉积物中无机碳形态分布的关键控制因子。研究发现，湖泊富营养化类型、湖泊初级生产力、C-N-P-Si的耦合作用、氮的硝化与反硝化作用及水-沉积物界面的扰动等均是影响沉积物中无机碳形态分布及水-沉积物界面碳通量和过程的重要机制。4．给出了浅水草型和深水藻型等2个不同类型湖泊沉积物中无机碳的主导形态，探讨了无机碳形态对湖泊生态系统碳循环的贡献及其差异性机制，阐释了无机碳形态对水-沉积物界面碳通量和碳过程及沉积物碳源／汇功能的控制作用机理。5．利用BSi，结合湖泊水体营养状况及生产力水平，反演了浅水草型和深水藻型等2个不同类型湖泊的富营养化进程。6．以无机碳形态研究为基础，紧密围绕湖泊水-沉积物界面碳源／汇功能及其转化机制这条主线，首次系统开展了内蒙古高原西部湖泊水-沉积物系统的碳循环研究，填补了该区湖泊碳循环研究的空白。上述研究成果对厘定内蒙古高原湖泊碳源汇的时空分布格局，为干旱半干旱区湖泊沉积物碳源汇功能的研究提供借鉴，为与湿润区湖泊的对比研究积累基础资料，为湖泊湿地资源的合理开发与保护利用提供科学依据等均有重要意义。更多还原

【Abstract】 Carbon （C） shares with nitrogen （N） and phosphorus （P） the characteristic of being the major chemical elements in the global biosphere, and the photosynthetic fixation of C by phytoplankton is accompanied by the uptake of major chemical elements such as N and P for diatoms. So the chemical, geological, biological, and physical processes of carbon are important to many fundamental geochemical processes. Interest in the biogeochemical cycles of important elements like C, N, P and trace elements has been heightened by issues associated with global, regional and local environmental problems caused by increased fluxes of C, N and P compounds arising from anthropogenic activities. Due to concern associated with the increase of atmospheric CO₂ concentrations and a future enhanced greenhouse effect, numerous studies have focused on the global carbon cycling. This increase has led researchers worldwide to examine the sources and sinks of carbon and to calculate carbon balances. Apart from the binding of carbon in peat lands, mineral soils and the tree layer vegetation, it is also present in large quantities in lake sediments, which constitute one of the few permanent sinks in the global carbon cycle.Therefore, this study was carried out on the Wuliangsuhai Lake （WLSH） and the Daihai Lake （DH） based on their representativeness on the mechanism and characteristic of eutrophication, and on the different mechanism of carbon form distribution in the water/sediment system. Based on the theories and methods of environmental geochemistry, biogeochemistry, pollution ecology and limnology, the form distribution, the geochemistry characters and the contribution to carbon cycling of carbon in the Wuliangsuhai Lake and the Daihai Lake are researched in this paper.To say concretely, the patter of horizontal distribution of dissolved inorganic carbon （DIC）, total inorganic carbon （TIC）, dissolved organic carbon （DOC） and total organic carbon （TOC） in overlying water and the form distribution of inorganic carbon （IC） in sediment of the two lakes are studied, which includes the impacts of environmental factors on the form distribution of inorganic carbon, the pulling function to the carbon cycling of the lake ecosystem by the eutrophication status and types. Meanwhile, the form transformation of IC and their contribution to carbon cycling in sediment, and the DIC fluxes across water-sediment interface in the two lakes are also discussed. In addition, based on accurate interpretation of the information of IC form distribution, allochthonous organic carbon （OC） and BSi archived in sediment cores, the palaeoenvironment and palaeoclimate of the two lakes and their catchments basins were well reconstructed, which may provide valuable database for the studies of environmental geochemical cycle and function transformation of source/sink of carbon in lakes sediment. The results are described as follows:1. Based on the calculation of fluxes of DIC across the water-sediment interface, there about 2.64×10⁴t DIC is released from sediment to overlying water in WLSH in summer （90 days）; there about 1.70×10⁴t DIC is released from sediment to overlying water in DH’s shoal water zone, while there about 2.00×10⁴t DIC transfers into sediment from overlying water across the water-sediment interface in DH’s deepwater area, thus there about 0.30×10⁴t DIC transfers into sediment in DH.2. For the first time, based on the accurate interpretation of the information of allochthonous OC and NH₂OH-HC1 form IC archived in sediment cores, the palaeoenvironment and palaeoclimate of the Daihai Lake and its catchment basin in recent 250 and 550 years are well reconstructed respectively. So the research does some significative works in rinding new effective indexes of palaeoenvironment and palaeoclimate studies.3. Because of the impacts of lake types especially eutrophication level and character, the key factors affecting the form distribution of IC are TOC, TN, Org-N, NH₄⁺-N and NO₃^--N in WLSH sediment, while TOC, TN, Org-N, water ratio, BSi, TP and inorganic phosphorus （IP） in DH sediment.The content of IC from biogenic origin and organic matter decomposition controlled by TOC, TN and Org-N, the pulling function to carbon cycling by coupling effects of C-N-P-Si and the exchange function of pore water are the key mechanisms affecting the forms distribution in sediments and the fluxes and processes of IC across the water-sediment interface.The nitrification and denitrification in sediment of shallow lake, the eutrophication character, the disturbance intension of water-sediment interface, the primary conductivity and the mass action law also play important roles in affecting the forms distribution in sediments and the fluxes and processes of IC across the water-sediment interface.4. The contributions to carbon cycling of IC forms rank as: NaCl form > NaOH form and NH₃-H₂O form > NH₂OH-HC1 form > HC1 form.Further, at a certain extent, the HCl form of IC also contributes to carbon cycling of IC, which is related to the rhizosphere environment of submerged macrophyte and emergent plant in WLSH; while the HCl form of IC does not contribute to carbon cycling of IC because of DH’s sediment lacking of impacts by aquatic organisms.5. The dominant forms of IC in sediment from WLSH and DH are NH₂OHHCl form and HCl form indicating that calcite and aragonite, which are the main source of IC, are the dominant carbonate minerals in the two lake sediment.The differences of NaCl form, NH₃·H₂O form and NaOH form IC between WLSH and DH sediment reveal that form distribution of the three IC forms are the key controlled factors of the fluxes and processes of carbon across the water-sediment interface, which further affect the function transformation of sediment as carbon source/sink. Meanwhile, the difference of vertical distribution of the three IC forms of DH indicate that the sediment in different lake areas play different role in functioning as carbon source/sink. 6. The DIC and TIC distributions in overlying water show that the contents of DIC and TIC in DH are higher markedly than those in WLSH, which mainly results from the photosynthetic fixation of DIC and TIC by submerged macrophyte of WLSH, stronger chemical weathering, more IC input by surface runoff and the enclosed character of DH and its catchment basin.The correlation between NH₄⁺-N, NO₃^--N, DTP, DRP, SiO₃^-2 and TIC, DIC, TOC, DOC indicate that the photosynthesis and respiration of phytoplankton in DH overlying water, which is related to the bio-geochemical cycling of carbon, is controlled by NH₄⁺-N, DTP, DRP and SiO₃^2- revealing the pulling function to carbon cycling by eutrophication level.7. The concentration levels of SiO₃^2- and BSi in the overlying water and surface sediment reflect the difference of eutrophication character between the two lakes. Further, based on the vertical distribution of BSi, TN and TOC in the sediment cores, the past eutrophication trends of WLSH and DH is well reconstructed.更多还原