Metal isotopes as chemical weathering tracers

金属同位素作为化学风化示踪剂

• 批准号: RGPIN-2020-05442
• 负责人: Phan, Thai
• 金额: $ 2.19万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750857
• 关键词: Metal; isotopes; chemical; weathering; tracers; Metal; isotopes; chemical; weathering; tracers

The rising global temperature is leading to increasing glacial melting and permafrost thawing, resulting in enhanced silicate, sulfide, and carbonate weathering. Elevated sulfide weathering in glaciated regions dominated by high physical erosion generates acidity that can dissolve carbonate, partially counteracting CO2 consumption by silicate weathering. Understanding the balance of the weathering fluxes, which affect the release or drawdown of CO2, is critical for understanding future global warming. Thus, there is a pressing need to develop reliable chemical weathering tracers which will require a comprehensive understanding of isotope fractionation processes. The long-term goal is to use metal isotopes to advance the understanding of metal cycles, which have important implications on the exploration of natural resources, fate and transport of contaminants, impacts of resource development such as mining, shale gas extraction, and geological carbon storage on the quantity and quality of surface water and groundwater. The specific goal for a five-year period (2020-2025) is to develop the applications of 7Li/6Li and 71Ga/69Ga as chemical weathering proxies, particularly in distinguishing silicate, sulfide, and carbonate weathering processes with the support of 87Sr/86Sr. This goal can be achieved through three highly innovative objectives: 1) Assess the role of secondary mineral formation and organic accumulation in controlling Li concentration and isotope composition in arid environments; 2) Determine the magnitudes and mechanisms of Ga isotope fractionation during continental weathering processes, through laboratory experiments and geochemical modelling; then experimental results will be used to interpret Ga isotope behavior in the Zackenberg River Catchment of Greenland; 3) Evaluate the Ga isotope geochemistry in sulfate rich and acidic environments by characterizing Ga isotopes in precipitates and hot spring waters in equilibrium with a variety of bedrock terrains; then the role of adsorption by iron colloids on Ga isotope fractionation during transport in rivers fed by Tamagawa hot springs (Japan) will be tested. Radiogenic Sr isotopes are mainly used as a tool to support the understanding of geochemical processes controlling Li and Ga isotope geochemistry. This research program will advance understanding of Ga isotope fractionation processes, thus, providing a foundation to use Ga isotopes as a geochemical tracer, particularly in tracing silicate vs. sulfide weathering processes, which is necessary for understanding future global warming. Understanding of Li cycles in arid environments will advance knowledge of economically significant sources of Li. Moreover, there is a shortage of highly qualified personnel (HQP) in Canada. HQP trained under this program will gain strong knowledge and technical skills in geochemistry to tackle scientific challenges regarding environmental issues related to natural resource development and climate change.

全球温度的上升导致冰川融化和多年冻结融化，从而导致硅酮，硫化物和碳酸盐风化增强。高物理侵蚀主导的冰川区域中硫化物风化会产生酸度，可以溶解碳酸盐，部分抵消硅酮风化的二氧化碳消耗。了解影响二氧化碳释放或缩减的风化通量的平衡对于理解未来的全球变暖至关重要。这是迫切需要开发可靠的化学风化示踪剂，这将需要对同位素分馏过程有全面的理解。长期目标是使用金属同位素来提高对金属周期的理解，金属周期对探索自然资源，污染物的命运和运输具有重要意义，资源开发的影响，例如采矿，页岩气提取以及地质碳存储对地表水和地下水的数量和质量。五年（2020-2025）的具体目标是开发7LI/6LI和71GA/69GA作为化学风化的代理，尤其是在区分硅胶，硫化物和碳酸盐风化过程中，并支持87SR/86SR。可以通过三个高度创新的目标来实现这一目标：1）评估二次矿物形成和有机积累在干旱环境中控制LI浓度和同位素组成中的作用； 2）通过实验室实验和地球化学建模，在连续风化过程中确定GA同位素分馏的尺寸和机制；然后，实验结果将用于解释格陵兰Zackenberg河流集水区中的GA同位素行为。 3）在富含硫酸盐和酸性环境中的GA同位素地球化学来评估珍贵的情况下的GA同位素，并在平衡中以各种基岩地形的平衡来表征GA的同位素；然后，将测试铁胶体在Tamagawa Hot Springs（日本）喂养的河流中的GA同位素分馏中增加的作用。放射性SR同位素主要用作支持控制LI和GA同位素地球化学的地球化学过程的工具。该研究计划将促进对GA同位素分馏过程的了解，从而为使用GA同位素作为地球化学示踪剂提供基础，尤其是在追踪硅胶与硫化物风化过程中，这对于理解未来的全球变暖是必不可少的。在干旱环境中对LI周期的理解将提高对经济上重要的LI来源的了解。此外，加拿大缺乏高素质的人员（HQP）。根据该计划培训的HQP将获得地球化学方面的强大知识和技术技能，以应对与自然资源开发和气候变化有关的环境问题的科学挑战。