陆地生态系统输入内陆水体的碳中仅有很小部分通过河流最终到达海洋，其余部分在运移中遗失，河流有机碳是碳转换的重要中间产物，对其不同时空变化规律的研究还比较缺乏。青藏高原山地河流对气候变化响应非常敏感，空间地理条件变化大，受人为活动影响小，是探讨有机质自然变化的理想对象。因此，本申请拟对高原东部小流域白龙江中有机碳的时空动态变化，特别是有机碳的降解和新生成等机制展开研究。通过对流域时空序列采样，分析河流中溶解有机质光谱特征，悬浮物C/N，颗粒态及溶解木质素的组成及13C及14C，结合地形变化、土地利用解析河流中有机碳的来源空间分布规律及控制因素，基于季节变化下有机碳的行为，尤其是不同水动力和温度条件探讨有机碳输送过程中的转换机制和规律。最后拟建立多元混合方程量化解析有机碳的来源份额的时空变化，阐述有机碳在山地河流中的降解和其它转化过程，为准确理解区域/全球碳循环提供科学基础。

Only a small fraction of carbon, the terrestrial ecosystem transporting into the inland waters, is discharged into the ocean, and the reminding carbon is lost under various biogeochemical processes. Organic carbon is one of the most important intermediate products in these processes. However, few studies have focused on the temporal and spatial variations of organic carbon. Mountainous rivers, originating from Qinghai-Tibetan Plateau, are ideal study area of organic carbon variations, where are sensitive to climate variability, less affected by anthropogenic activities, and have large spatial range of geological variability. Spatial and temporal samples will be collected in the Bailong River, and the C/N ratios of suspended matters, spectral characters, lignin, as well as the stable and radiocarbon isotopes will be analyzed in this study. Combined with geographic variations and land use, the spatial variations of organic carbon sources and the control mechanisms will be investigated. Based on the seasonal variations of organic carbon behaviors, the transform mechanisms of organic carbon under various hydrological and temperature conditions will be explored. Finally, the temporal and spatial sources of organic carbon will be quantified based on multiplex mixed equations, the biogeochemical processes such as, transform and degradation, will be clarified, in order to provide the scientific proof for understanding the biogeochemical processes and carbon budget of mountainous rivers, originating from Qinghai-Tibetan Plateau.