Collaborative Research: Magnitude and Pathway of Gaseous Atmospheric Mercury Deposition in Forests

合作研究：森林中气态大气汞沉积的幅度和途径

• 批准号: 1848212
• 负责人: Daniel Obrist
• 金额: $ 62.23万
• 依托单位: University of Massachusetts Lowell
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-01-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1848212&HistoricalAwards=false
• 关键词: Collaborative; Research; Magnitude; Pathway; Gaseous

Mercury (Hg) is released from both natural sources and human activities. The goal of this project is to make measurements of mercury for an entire year in two contrasting forest locations. This rich dataset will be used to better understand how Hg moves through trees, soil, and the atmosphere. Understanding the distribution of mercury is important because it is a toxic substance, which can cause negative neurological effects in humans and react with other atmospheric gases. The knowledge from this project will be useful for assessing the global distribution of a mercury so that international recognized goals for reducing Hg pollution can be achieved. Additionally, the project will provide partial support for a postdoctoral researcher, two graduate students, and one undergraduate student per year.Atmospheric mercury deposits via various dry and wet (e.g., rainfall) deposition processes, including gaseous mercury uptake by plants. Mercury in vegetation is transferred to soils when plants die off or shed leaves, contributing 54-94% of mercury in soil. In the absence of direct measurements, gaseous elemental mercury (Hg[0]) deposition is inferred from litterfall and passive membranes, yet these are not ideal proxies for net Hg(0) deposition as they don?t account for re-emission. Consequently, first objective of this project is to quantify the magnitude and temporal dynamics of net gaseous dry Hg(0) deposition (sum of gross deposition minus emission) in two forests with different seasonalities, a deciduous temperate forest and an evergreen subtropical rain forest. Net Hg(0) deposition will be measured using micrometeorological measurements on large towers, the only available method for direct, non-intrusive and time-extended measurements of net Hg(0) exchange at the ecosystem level encompassing all underlying sinks and sources. The second objective is to partition Hg(0) fluxes into canopy and soil contributions via deployment of two corresponding flux systems - one above the forest canopy to measure ecosystem-level Hg(0) exchange and a second system below the canopy to quantify soil contributions. Canopy Hg(0) fluxes will be calculated by difference. Flux partitioning will provide annual, seasonal and diurnal Hg(0) sink (e.g., to canopies) and source strengths (e.g., from soils) needed to constraint Hg(0) deposition in global and regional chemical transport models. Finally, the third goal of this work is to elucidate pathways of deposition by comparing Hg(0) fluxes to those of carbon dioxide, ozone, water vapor, and carbonyl sulfide. All these trace gases have different sinks and sources in ecosystems and vary in their degree of canopy, stomatal, mesophyll and soil contributions to fluxes. Comparison among fluxes, including seasonality, diurnality and component fluxes will allow us to quantify the degree to which Hg(0) exchange is coupled to photosynthetic activity, stomatal conductance, enzymatic activity within leaves, external cuticular uptake and soil exchange.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

汞（Hg）从自然来源和人类活动中释放出来。该项目的目标是在两个截然不同的森林地点测量一整年的汞含量。这个丰富的数据集将用于更好地了解汞是如何在树木、土壤和大气中移动的。了解汞的分布很重要，因为它是一种有毒物质，会对人类的神经系统造成负面影响，并与其他大气气体发生反应。该项目的知识将有助于评估汞的全球分布，从而实现国际公认的减少汞污染的目标。此外，该项目每年将为一名博士后研究员、两名研究生和一名本科生提供部分支持。汞通过各种干湿（如降雨）沉积过程在大气中沉积，包括植物对气态汞的吸收。当植物死亡或落叶时，植被中的汞会转移到土壤中，占土壤中汞的54-94%。在没有直接测量的情况下，从凋落物和被动膜中推断出气态元素汞（Hg[0]）沉积，但这些并不是净汞(0)沉积的理想代表。T表示再发射。因此，本项目的第一个目标是量化两种不同季节森林（落叶温带森林和亚热带常绿雨林）中净气态干汞(0)沉积（总沉积减去排放量的总和）的大小和时间动态。净汞(0)沉积将使用大型塔上的微气象测量来测量，这是在包括所有底层汇和源的生态系统水平上直接、非侵入性和长时间测量净汞(0)交换的唯一可用方法。第二个目标是通过部署两个相应的通量系统，将Hg(0)通量划分为冠层和土壤贡献——一个在森林冠层之上，用于测量生态系统水平的Hg(0)交换，另一个在冠层之下，用于量化土壤贡献。冠层汞(0)通量将通过差值计算。通量分配将提供限制全球和区域化学运输模式中汞(0)沉积所需的年度、季节和日汞(0)汇（例如，到冠层）和源强度（例如，来自土壤）。最后，本工作的第三个目标是通过比较汞(0)通量与二氧化碳、臭氧、水蒸气和羰基硫化物的通量来阐明沉积途径。这些微量气体在生态系统中有不同的汇和来源，其对林冠、气孔、叶肉和土壤通量的贡献程度也各不相同。通量之间的比较，包括季节性、昼夜性和组分通量，将使我们能够量化Hg(0)交换与光合活性、气孔导度、叶片内酶活性、外部角质层吸收和土壤交换的耦合程度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Vegetation uptake of mercury and impacts on global cycling

• DOI: 10.1038/s43017-021-00146-y
• 发表时间: 2021-03
• 期刊: Nature Reviews Earth & Environment
• 影响因子: 42.1
• 作者: Jun Zhou;D. Obrist;A. Dastoor;M. Jiskra;A. Ryjkov

Global Mercury Assimilation by Vegetation

• DOI: 10.1021/acs.est.1c03530
• 发表时间: 2021-10-07
• 期刊: ENVIRONMENTAL SCIENCE & TECHNOLOGY
• 影响因子: 11.4
• 作者: Zhou, Jun;Obrist, Daniel
• 通讯作者: Obrist, Daniel