中亚地区伊塞克湖沉积记录的近千年环境演化过程与机理

Considering the key issues of water resources and ecological environments in arid regions of Central Asia，Lake Issyk-Kul and its catchment are selected for the study on the process and its mechanism of climate and eco-environmental changes recorded in the lake sediments. Firstly, through developing the datasets on climate and environment in the lake catchment, together with the principles combined with limnology and paleolimnolohy, we try to calibrate climatic and environmental proxies from lake sediments, and then to establish quantitatively effective series of proxies for lake environments, regional climate and human impacts. Secondly, by analyzing environmental sequences from multi-proxies in lake sedimentary records with the aid of the mathematical models，combining with analysis of the terraces and historical documents of lakes basin, we intend to quantitatively reconstruct the evolutionary sequences of salinity variations, water level fluctuations and human activities in the past thousand years. With this, we can obtain the information on regional hydrothermal combinations during Medieval Warm Period and the Little Ice Age, and diagnose the lake ecological environmental events, reveal the characteristics and regulations of lake ecological response to different climatic conditions. Finally, by comprising of the sedimentary records from different types of lakes, the pattern and principle of lake environment evolution will be discovered and environment change mechanism of mountain lake under the disturbance of nature and human influence will be probed, which will provide scientific support for lake restoration and protection in arid regions of Central Asia.

基于中亚干旱区湖泊流域资源与生态环境所面临的关键科学问题，本项研究选择吉尔吉斯坦伊塞克湖开展湖泊沉积记录的气候环境演化过程与机理研究。首先，通过建立湖泊流域气候环境数据集，依据湖沼学技术方法，进行沉积记录的气候环境可代用性标定，确立定量表征湖泊环境及区域气候的有效沉积指标系列。然后，通过典型沉积钻孔岩芯的多环境代用指标序列分析，借助于数理方法及模型，结合流域湖泊阶地与历史文献记载分析，定量重建过去千年来湖泊矿化度变化、水位波动序列。将湖泊沉积记录与区域树轮及冰芯等记录比较，分析中世纪暖期及小冰期等典型时期区域水热组合特征，剖析并诊断湖泊生态环境事件，揭示不同气候背景下湖泊生态环境响应的特征与规律。最后，通过不同区域湖泊环境变化的综合比较，研究不同区域气候变化背景下湖泊生态演化特征及差异，探讨中亚干旱区湖泊生态环境变化的机理，为干旱区湖泊及流域的环境治理与规划提供科学依据。

中亚国家和我国西北领土相连，一些重要湖泊处于同一水系，在气候、生态环境和生物资源等方面有很大的相似性与相关度，开展与中亚国家在生态环境领域内的合作，有利于解决我国西北地区面临的生态环境问题，也有利于科学地协调跨境河流的整体水资源布局。因此，本项研究针对干旱区湖泊资源与环境变化的特点，重点选择吉尔吉斯坦伊塞克湖及其流域，并通过其相邻区域不同水土环境数据比较分析，结合湖泊沉积岩芯多气候环境代用指标包括总有机碳（TOC）、总氮（TN）和正构烷烃生物标记物以及有机氯农药（OCPs）、多环芳烃（PAHs）、磁化率、粒度和多种元素等，开展了吉尔吉斯坦伊塞克湖沉积记录的环境变化及机理研究。通过沉积记录与器测多种资料比较，建立了湖泊沉积环境代用指标和湖泊水位之间的函数关系，明确了沉积物OCPs和PAHs变化指示了流域人类活动的强度。由于人为内源和“全球蒸馏效应”外源的不同，空间尺度上人类活动造成的环境污染程度存在显著差异，但是流域内污染的生态风险小或者偶发生态负效应。在此基础上，通过沉积岩芯多环境指标综合比较分析，恢复了伊塞克湖近千年来的水位变化，划分了四个气候环境变化阶段，识别了多次水文环境事件，并与相邻区域树轮及冰芯等记录进行比较，揭示了不同环境阶段气候和人类活动驱动的过程与机理。总体上，在区域水土生态环境特征与生态风险评估、沉积记录的气候环境代用指标确定以及湖泊流域环境演化过程及机理等方面取得了进展，也填补了研究区湖泊流域环境基础数据方面的空白。研究成果对于正确认识未来气候变化对于干旱区山地生态环境的影响、跨境流域水土环境保护和合理利用以及有效管理均具有重要意义。