Understanding the Modern and Past Mercury Biogeochemical Cycle Using Hg Stable Isotopes

使用汞稳定同位素了解现代和过去的汞生物地球化学循环

• 批准号: RGPIN-2018-06569
• 负责人: Bergquist, Bridget
• 金额: $ 5.25万
• 依托单位: University of Toronto
• 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=751221
• 关键词: Understanding; Modern; Past; Mercury; Biogeochemical

The long-term goal of my research program is to use Hg isotopes to improve our understanding of the Hg biogeochemical cycle and to develop Hg isotopes as a proxy of past environmental changes. Mercury is a globally distributed metal that bioaccumulates in aquatic food webs leading to dangerous exposure in humans and wildlife. Mercury is often emitted to the atmosphere in its reduced form, gaseous elemental Hg (GEM), by both natural and anthropogenic sources. GEM is relatively stable and has a long residence time (~1 yr), which allows it to be distributed globally. Eventually GEM is oxidized and deposited to terrestrial and aquatic systems quickly (hours to weeks). One of the major complexities of the Hg cycle is that after deposition, Hg can be reduced back to GEM and emitted back to the atmosphere. This results in primary sources making up less than half of the Hg emissions to the atmosphere (30% anthropogenic, 10% natural) with 60% of inputs to the atmosphere being Hg re-emissions dominantly from soils and the ocean. Many key knowledge gaps still hinder our understanding of both the modern and past Hg cycle and make it challenging to predict how changes in emissions and climate will affect the Hg cycle. For example, assessing the relative contributions of different anthropogenic sources versus re-emissions on local, regional and global scales is a huge challenge and is often dependent on models without enough constraints from data. Also, a recent assessment of GEM exchange to and from soils highlighted that very large uncertainties still exist especially in forested ecosystems. A rapidly growing tool to study Hg is Hg stable isotope geochemistry, which was largely driven by the discovery of large mass independent fractionation (MIF) of Hg isotopes. My Discovery program will focus on three goals that are exciting new areas where Hg isotopes are likely to make large impacts on the field of Hg research: (1) the development and application of new methods to measure Hg concentrations and isotopic compositions of atmospheric Hg species, (2) the use of Hg isotopes to quantify and understand sources and remobilization of Hg in soils, and (3) the development and testing of Hg and Hg isotopes as a proxy of ancient volcanic emissions. Objectives 1 and 2 will advance modelling and assessment of sources of Hg to the atmosphere and to soils through much needed experimental studies, novel development of samplers for collection and isotopic analysis of Hg, and fieldwork to verify and apply new techniques. The third objective will investigate a primary natural source of Hg to the atmosphere, volcanism, and the isotopic signatures of volcanic Hg species along with how these signatures are preserved in geological records. The isotopic characterization of this geogenic source of Hg will contribute to our understanding of the modern Hg cycle and will establish the baseline for Hg isotopes as a reliable tracer of ancient volcanic emissions.

我的研究计划的长期目标是使用HG同位素来提高我们对HG生物地球化学周期的理解，并开发HG同位素作为过去环境变化的代理。汞是一种全球分布的金属，在水生食物网中产生生物累积的金属，导致人类和野生动植物的危险暴露。汞通常以自然和人为的来源以其降低形式的气态元素Hg（GEM）发射到大气中。宝石相对稳定，停留时间很长（约1年），可以在全球范围内分布。最终，宝石被氧化并沉积在陆地和水生系统上（数小时至几周）。 HG循环的主要复杂性之一是，在沉积后，可以将HG简化回GEM，然后散发回大气。这导致主要来源构成了大气排放的一半（30％人为，自然10％），而大气中有60％的投入是HG从土壤和海洋中占主导地位。许多关键知识差距仍然阻碍了我们对现代和过去的HG周期的理解，并使预测排放和气候变化如何影响HG周期变得具有挑战性。例如，评估不同人为来源的相对贡献与对本地，区域和全球量表的重新排放的相对贡献是一个巨大的挑战，通常取决于模型，而没有数据的足够约束。同样，最近对与土壤的GEM交换的评估强调，在森林生态系统中仍然存在非常大的不确定性。 HG稳定的同位素地球化学是一种快速增长的研究HG，它在很大程度上是由于发现大型质量独立分馏（MIF）的HG同位素的驱动。我的发现计划将集中于三个令人兴奋的新领域，在这些目标中，HG同位素可能会对HG研究领域产生很大影响：（1）开发和应用新方法来测量HG浓度和大气HG物种的同位素组成，（2）HG同位素的使用来量化和理解HG的来源和探索HG和HG的HG和HG的HG，以及HG的HG，以及HG的HG，（3）（3），（3），（3）（3）（3），（3）（3），（3）（3）（3），（3）（3），（3）（3）（3）（3），（3）（3）（3）（3）（3）（3），（3），（3）的HG同位素（3）使用HG。作为古代火山排放的代理。目标1和2将通过急需的实验研究，新的采样器开发进行收集和同位素分析以及验证和应用新技术的现场工作，将HG来源的建模和评估推向大气和土壤的建模和评估。第三个目标将调查汞的主要自然来源到大气，火山和火山汞种类的同位素特征，以及这些特征如何保存在地质记录中。这种地球源的地球来源的同位素表征将有助于我们对现代HG周期的理解，并将建立HG同位素作为古代火山排放的可靠示踪剂的基线。