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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716337
• 关键词: 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 (20202025) 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.

全球气温上升导致冰川融化和永久冻土融化，导致硅酸盐、硫化物和碳酸盐风化作用增强。在以高物理侵蚀为主的冰川地区，高硫化物风化产生的酸性可以溶解碳酸盐，部分抵消硅酸盐风化对二氧化碳的消耗。了解影响CO2释放或减少的风化通量的平衡对于了解未来全球变暖至关重要。因此，迫切需要开发可靠的化学风化示踪剂，这将需要全面了解同位素分馏过程。 长期目标是利用金属同位素来促进对金属循环的理解，这对自然资源的勘探，污染物的归宿和运输，资源开发（如采矿，页岩气开采和地质碳储存）对地表水和地下水的数量和质量的影响具有重要意义。具体目标是在五年内（2020 - 2025年）开发7 Li/6Li和71 Ga/69 Ga作为化学风化指标的应用，特别是在87 Sr/86 Sr的支持下区分硅酸盐、硫化物和碳酸盐风化过程。这一目标可以通过三个高度创新的目标来实现：1）评估次生矿物形成和有机积累在干旱环境中控制Li浓度和同位素组成的作用; 2）通过实验室实验和地球化学模拟确定大陆风化过程中Ga同位素分馏的幅度和机制;然后利用实验结果解释格陵兰Zackenberg河流域Ga同位素行为;第三章通过表征沉淀物和温泉沃茨中与各种元素平衡的Ga同位素，评价富硫酸盐和酸性环境中Ga同位素地球化学。基岩地形;然后将测试铁胶体的吸附作用在由玉川温泉（日本）注入的河流中的迁移过程中对Ga同位素分馏的作用。放射成因Sr同位素主要用于支持对控制Li和Ga同位素地球化学的地球化学过程的理解。 这项研究计划将促进对Ga同位素分馏过程的理解，从而为使用Ga同位素作为地球化学示踪剂提供基础，特别是在追踪硅酸盐与硫化物风化过程中，这对于了解未来全球变暖是必要的。了解干旱环境中的锂循环将促进对锂的经济重要来源的认识。此外，加拿大缺乏高素质人才。在该计划下接受培训的HQP将获得地球化学方面的丰富知识和技术技能，以应对与自然资源开发和气候变化相关的环境问题的科学挑战。