Collaborative Research: Vegetation assimilation as a source of mercury in a salt marsh ecosystem and implications for soil and tidal water exposures

合作研究：植被同化作为盐沼生态系统中汞的来源以及对土壤和潮汐水暴露的影响

• 批准号: 2027019
• 负责人: Inke Forbrich
• 金额: $ 8.77万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2027019&HistoricalAwards=false
• 关键词: Collaborative; Research; Vegetation; assimilation; source

The goal of this award is to determine the origin and fate of mercury in a salt marsh ecosystem in the Plum Island Sound of Massachusetts and potential export to near shore coastal oceans. Mercury is a potent neurotoxin and leading cause for fish consumption advisories in the U.S and across the world. Along the U.S. East Coast, salt marsh sparrows have shown harmful exposures to mercury with elevated blood levels posing risks for reproductive outputs. The origin of mercury in these salt marshes is largely unknown. Possible reasons for high mercury exposure are contributions from runoff from adjacent watersheds or atmospheric inputs from legacy industrial impacts. This award will study the role of direct plant uptake of atmospheric mercury by salt marsh plants as the mercury source for these salt marsh ecosystems. In this tidal system, an additional focus lies on the transfer of mercury to soils by the plants and with death of the plants its export to the coastal ocean. The award will train and involve graduate and undergraduate students in the research.This award aims to quantify mercury sinks and sources and their relationships to plant primary productivity, tissue turnover rates, and soil dynamics, in a salt marsh ecosystem where some of the highest biological mercury exposures have been reported. The first hypothesis is that that plant mercury assimilation is the dominant source of mercury in this estuary where salt marshes dominate in areal extent (50 to 90% of surface area). The second hypothesis is that vegetation assimilation of mercury is incorporated into soils upon plant senesce leading to high mercury accumulation in soils, which ultimately is mobilized to tidal water leading to net export of mercury from salt marshes to tidal water. This is analogue to the “outwelling” hypothesis for carbon that proposes that salt marshes produce an excess of autochthonous carbon over what is degraded and stored resulting in net export to the coastal ocean where it stimulates ocean net primary production. Proposed measurements include quantification of atmospheric mercury deposition inputs via deployment of a micrometeorological flux-gradient system that allows to measure ecosystem-level gaseous atmospheric mercury fluxes including plant mercury assimilation, along with detailed vegetation mercury dynamics and other deposition processes. Spatial transect sampling of tidal water from the ocean through the tidal water up to the freshwater headwater will be conducted and analyzed for mercury species (dissolved, particulate, methyl-mercury and mercury bound contained in wrack detritus) in order to assess lateral exchanges between salt marsh and tidal water. Finally, distribution patterns of total mercury and methylated mercury in salt marsh soils will be characterized to constrain processes — both natural and anthropogenic — that lead to mercury accumulation in these 2,500-to-3,500 year old soils.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.

该奖项的目的是确定汞在马萨诸塞州普拉姆岛湾盐沼生态系统中的来源和归宿，以及向近海岸海洋的潜在出口。汞是一种强大的神经毒素，也是美国和世界各地鱼类消费的主要原因。沿着美国东海岸，盐沼麻雀已经显示出有害的汞暴露，血液中的汞水平升高，对生殖产出构成风险。这些盐沼中汞的来源在很大程度上是未知的。汞暴露量高的可能原因是来自邻近流域的径流或遗留工业影响的大气输入。该奖项将研究盐沼植物作为盐沼生态系统的汞来源直接吸收大气汞的作用。在这种潮汐系统中，另一个重点是汞通过植物转移到土壤中，并随着植物的死亡而出口到沿海海洋。该奖项将培训研究生和本科生参与研究，旨在量化汞汇和汞源及其与植物初级生产力、组织周转率和土壤动态的关系，在盐沼生态系统中，一些最高的生物汞暴露已被报道。第一个假设是，植物汞同化是汞的主要来源，在这个河口，盐沼占主导地位的面积范围（表面积的50%至90%）。第二个假设是，植物衰老后，植被对汞的吸收被纳入土壤，导致土壤中汞的大量积累，最终被动员到潮汐水中，导致汞从盐沼净输出到潮汐水中。这类似于碳的“外向”假说，该假说提出盐沼产生的本地碳超过了退化和储存的碳，导致净出口到沿海海洋，刺激海洋净初级生产。拟议的测量包括通过部署微气象通量梯度系统量化大气汞沉积输入，该系统允许测量生态系统层面的气态大气汞通量，包括植物汞同化，沿着详细的植被汞动态和其他沉积过程。将对从海洋到淡水源头的潮汐水进行空间样带取样，并分析汞的种类（溶解汞、颗粒汞、甲基汞和残骸碎屑中所含的汞），以评估盐沼和潮汐水之间的横向交换。最后，盐沼土壤中总汞和甲基化汞的分布模式将被描述为限制导致汞在这些2,500至3,500年的土壤中积累的自然和人为过程。该奖项反映了NSF的法定使命，并被认为值得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来支持。