纵向岭谷区河流碳输送及水-气界面CO2释放研究-以长江上游龙川江为例

Rivers are incredibly important component of the environment, linking and sustaining terrestrial and marine ecosystems, and are thus gaining international significance for their potentially important role in the global carbon cycle. Rivers transport organic and inorganic carbon to the ocean or downstream, and return part of carbon to the atmosphere. The former represents a carbon sink, while the latter represents an atmospheric CO2 source. Fluvial carbon fluxes and water-air CO2 emissions especially under anthropogenic activities and climate changes are particularly the focus of carbon cycling. However, processes and mechanisms controlling CO2 emission and riverine carbon transports are poorly understood, especially carbon emission from monsoon climate driven rivers is scarce. These factors are very important in understanding the role that rivers play in the global and regional carbon cycle. This proposal seeks to obtain a comprehensive understanding of biogeochemical cycling of carbon in a typical monsoon climate river-Longchuanjiang in the upper Yangtze River. Emphasis will be placed on the source, flux of carbon and mechanisms of high aquatic pCO2 production. Our objectivities are to 1) examine carbon characteristics (DOC, POC, DIC, δ13CDIC, δ13CDOC, δ13CPOC, pCO2, H2CO3, HCO3-, CO2, CO32-) in relation to land use and hydrology at multiple spatiotemporal scales covering diurnal and seasonal (spring, summer, autumn and winter), as well as main channel and different-order streams; 2) quantify the fluxes of carbon and suspended particulate material (SPM) and their relations to human activities/land use and hydrology; 3) quantify water-air interface CO2 emission using in situ infrared analyzer and newly developed carbon diffusion model; 4) use isotopic carbon approach (stable δ13C), key environmental factors and biological activity to distinguish sources of carbon and to unravel controlled mechanisms on riverine carbon flux and emission. The research will lead to a new understanding of aquatic ecosystems and their role in carbon cycle. The expected outcomes will develop biogeochemical theory for subtropical river and serve for ecological security in the rivers locating at the Longitudinal Range-Gorge Region.

研究河流的碳形态、各过程碳通量及其影响因素对了解淡水生态系统在全球碳的生物地球化学循环中的作用至关重要。我国季风性气候控制区域的纵向岭谷区河流的碳输送正影响全球及区域尺度的碳评估，但目前的研究极少关注径流变化下河流的碳通量尤其是河流水-气界面碳通量规律及驱动机制。本项目将利用密集周年取样方式，综合运用生态水文学、生物地球化学、多元统计及同位素等技术和手段，以长江上游龙川江为例，研究我国西南纵向岭谷区径流变化及人为活动影响下的河流的碳循环、影响因素及驱动机制。揭示（1）碳的格局、来源、输送通量及其对水文变化的响应；（2）多时（昼夜及季节）空（干流和不同等级支流）尺度上的水-气界面碳交换及驱动因素；最终完成河流纵向和垂直方向的碳通量的综合评估。本研究将丰富我国流域生态学及生物地球化学循环理论，发展和完善河流的碳循环机制，对认识变化环境下的纵向岭谷区河流物质循环具有突出的科学意义。

项目背景.研究河流的碳形态、各过程碳通量及其影响因素对了解淡水生态系统在全球碳的生物地球.化学循环中的作用至关重要。我国季风性气候控制区域的纵向岭谷区河流的碳输送正影响全球及区域尺度的碳评估，但目前的研究极少关注径流变化下河流的碳通量尤其是河流水-气界面碳通量规律及驱动机制。本项目将利用密集周年取样方式，综合运用生态水文学、生物地球化学、多元统计及同位素等技术和手段，以长江上游龙川江为例，研究我国西南纵向岭谷区径流变化及人为活动影响下的河流的碳循环、影响因素及驱动机制。..主要研究内容.（1）河流碳（有机及无机碳）时空格局及其控制因子.（2）河流干流及典型支流纵向碳通量的时空异质性.（3）河流水-气界面碳交换及驱动因素..重要结果.1. 阐明龙川江水体pCO2和界面CO2通量的时空格局及与环境因子的关系.2. 建立河流pCO2与DOM化学多样性及养分化学计量比关系，构建基于光谱学参数的DOC预测模型.3. 揭示纵向岭谷河流-龙川江DOC可生物降解规律及关键控制因子，阐明降解过程中DOM质量变化，建立基于光谱学的DOM降解统计学模型.4. 揭示城镇化进程中养分变化对水体CO2的影响及CO2通量情况.5. 量化我国湖泊、水库温室气体释放量，阐明温室气体释放的关键控制因素，提出水库温室气体减排-富营养化控制的双赢思路..关键数据.1. 龙川江水体基础理化指标、CNP形态指标、CO2溶存浓度及通量；.2. 龙川江水体DOM化学多样性、DOC生物降解率和流域土地利组成..科学意义.阐明龙川江水体pCO2及界面通量变化规律与关键控制因素，揭示pCO2对城镇化、养分及DOM质量的响应关系；阐释DOM迁移转化与河流连续体的关系，构建DOC的预测模型；揭示河流DOM成分、分子大小和来源等信息与BDOC的关系，建立基于光谱学的DOM降解统计学模型，预测变化环境下DOC降解规律及环境意义，初步形成DOM-pCO2-BDOC的理论体系。丰富我国流域生态学及生物地球化学循环理论，发展和完善河流的碳循环机制，对认识变化环境下的纵向岭谷区河流物质循环具有突出的科学意义。

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