冰川流域生物活性Fe的迁移转化及冰冻圈过程的影响机制研究

Rapid shrinkage of the Cryosphere results in an obvious increase of meltwater runoff, evidently enhances the water-soil/rock interactions, and then leads to largely release of bioavailable Fe, and eventually influences the ecological system and carbon cycles in oceans. Studies found that the spatial variations of bioavailable Fe concentrations is extremely significant, resulting in a large error of estimated Fe fluxes and its influence evaluated on the ecological system and carbon cycles in oceans. However, the magnitude of the concentrations/fluxes of bioavailable Fe from glacial meltwater and its environmental significance remained unknown. Thus, it is extremely necessary to study the coupled studies of meltwater hydrochemistry processes. Based on snow cover/soil hydrothermal processes, glacier/permafrost hydrological processes, water chemistry process and soil/plant investigation, together with runoff-producing and flow tracing and incubation experiments, we are going to separate the sources of bioavailable Fe, to analyze the temporal and spatial variations of the concentrations and fluxes of bioavailable Fe and its relationship with plant coverage, light, organic ligand and so on, and then to reveal the migration and transformation of bioavailable Fe and the varying pattern of bioavailable Fe fluxes. We are going to quantity the relationship between meltwater runoff and hydrochemistry process, to identify the influencing pattern of the Cryospheric process to river runoff/sediment processes and the chemical process of bioavailable Fe, to establish a conceptual model about the chemical process of bioavailable Fe response to the degradation of the Cryosphere, and then to reveal the pattern of the Cryospheric process influencing the migration and transformation of bioavailable Fe. We hope that this study will lay the foundation for estimating the fluxes of meltwater-sourced Fe and for evaluating its influence on the ecological system.

冰冻圈加速退化导致融水径流明显增加、水-土/岩作用显著增强、生物活性Fe大量释放，最终影响海洋初级生产力和碳循环！研究发现Fe浓度的空间差异很大，以致由点向面外推的通量估算及其影响评估的误差较大。然而，冰川融水源Fe的浓度/通量的数量级、变幅及环境意义究竟如何？目前还不清楚！为此急需开展冰冻圈水文水化学过程的耦合研究。基于典型冰川流域积雪/土壤水热-冰川/冻土水文-水化学过程监测及土壤植被调查，结合产汇流示踪和融水培养试验，解析Fe来源，辨析Fe浓度/通量的时空变化过程/特征及其与植被盖度、光线、有机配体等的相关关系，揭示Fe的迁移转化及通量变化规律；量化融水径流与水文水化学过程的关系，识别冰冻圈过程对河流径流/泥沙过程及Fe化学过程的影响规律，交互对比分析，建立Fe化学过程响应冰冻圈退化的概念性模型，揭示冰冻圈过程对Fe迁移转化的影响机制，为融水源Fe的通量估算及其生态影响评估奠定基础。

冰川加速消融导致融水径流明显增加、水-土/岩作用显著增强、生物活性铁大量释放，最终将影响海洋初级生产力和碳循环！由于铁浓度的空间差异很大，以致由点向面外推的通量估算及影响评估误差较大。研究内容：冰川源可溶性铁（dFe）和可溶性有机碳（DOC）浓度的时空变化过程及迁移转化规律、dFe和DOC通量的变化过程及其时空变化规律、以及冰川消融对dFe和DOC迁移转化的影响机制。重要成果：亚洲冰川dFe和DOC的释放率分别为23.8 Gg/a和194 Gg/a，阿拉斯加冰川的释放率分别为71.1 Gg/a和98 Gg/a，欧洲中部冰川的释放率分别为3.5 Gg/a和2.8 Gg/a，斯瓦尔巴德/扬马延岛冰川的释放率分别为2.1 Gg/a和165 Gg/a。低纬度冰川dFe的释放率为7.4 Gg/a，冰岛冰川的释放率为1.3 Gg/a；加拿大西/美国冰川DOC的释放率为16 Gg/a，加拿大北极冰川的释放率为110 Gg/a。亚洲冰川内DOC的储量为8800-13800 Gg。全球冰川dFe和DOC的释放率分别为185 Gg/a和786 Gg/a，南极冰盖DOC的释放率为255-299 Gg/a。在有冰川补给的河流中一些有毒或有害元素的浓度已经超过了饮用水标准，所以有融水补给的高山河流可能面临着水质变差或恶化的潜在风险，开展径流变化与水质变化关系的监测十分重要。关键数据：采集并获取了一个完整消融期内亚洲三条典型冰川径流中主要离子、微痕量元素和有机碳浓度的逐日资料，以及气温、降水和流量的逐日资料；收集并获取了全球已发表的冰川径流中主要离子、铁、硅和有机碳的流域平均浓度资料，同时收集并获取了全球不同区域冰川年平均径流量的模拟资料。科学意义：首次评估了区域冰川DOC的释放率，准确评估并修订了前人估算的全球冰川DOC的释放率；首次评估了区域及全球冰川dFe的释放率，填补了国际上的研究空白。证明了冰川是dFe和DOC的重要来源，指出先前研究可能没有充分认识到冰川作为铁和有机碳来源的重要性，预计冰川在全球铁循环和碳循环中的重要性可能会越来越显著。本研究有助于深刻认识未来的冰川/冰盖消融对下游水生生态系统和全球碳循环的影响。