权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Collaborative Research: Halocarbon Biogeochemistry in Coastal Wetland Ecosystems- Exploring the Transition from Forested Wetland to Salt Marsh

合作研究：滨海湿地生态系统中的卤碳生物地球化学——探索森林湿地到盐沼的转变

基本信息

批准号：
1530375
负责人：
Robert Rhew
金额：
$ 7.74万
依托单位：
University of California-Berkeley
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-08-01 至 2019-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1530375&HistoricalAwards=false
关键词：
Collaborative Research Halocarbon Biogeochemistry Coastal

项目摘要

The relatively flat southeastern US coastal plain, from North Carolina to Texas, is particularly susceptible to sea level rise. As sea level rises, the boundary between the low-lying coastal freshwater forest and high marsh moves upslope. Highly productive forested wetlands are replaced successively by degraded wetlands and eventually by coastal salt marsh. Not only does saltwater intrusion change vegetation composition, high halide levels (called halogens) can interact with the large pool of soil organic matter through halogenation processes that are still poorly understood. These halogenation processes are important to elucidate as they produce volatile halocarbons that act as ozone-depleting compounds in the atmosphere. Halogenation of organic matter may also affect the decomposition rates of organic matter. This interdisciplinary research will improve our understanding of chlorine and bromine biogeochemistry and demonstrate the importance of halogens in carbon cycling. This collaborative research represents a new collaboration between four investigators with different specialties from universities in the northeast, southeast and western United States. Graduate and undergraduate students will have opportunities to interact with citizen scientists in an on-going EarthWatch project and learn how to disseminate the scientific knowledge to the general public. This study will also raise the awareness of the impacts of sea level rise on low-lying coastal areas in the Southeastern US.Halogens have historically been treated as inert elements in natural humification processes. However, numerous recent studies have demonstrated that chlorine and bromine are active components in C cycles. The overall goal of this research is to assess novel decomposition process routes of terrestrial organic matter in forested wetlands with high levels of chloride and bromide. The research project includes both field investigations and controlled experiments to determine the impacts of sea level rise on C and halogen biogeochemical cycles along salinity gradients in Winyah Bay, South Carolina. Fluxes of halogenated ozone depleting C compounds and greenhouse gases, as well as concentrations of organochlorine and organobromine in soil and litter and water will be quantified along salinity transects and within controlled plots. The research team contends that the novel method of determining X-ray absorption near edge structures (XANES) of halogenated organic matter in soil and detritus layers, coupled with measurements of halocarbon emission and composition in water using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), will be useful in understanding the roles of halogens in C cycling. Determining the seasonal variation of halocarbon in air, soil, and water from freshwater forested wetland, salt-degraded wetland, and salt marsh sites, representing the transition of coastal wetland under sea level rise, will be useful in developing a mechanistic and landscape understanding of how sea level rise affects decomposition, humification, and halogenation processes of terrestrial organic matter in coastal wetlands. The controlled field experiments using different concentrations of chloride and bromide waters would illustrate their roles in humification and decomposition processes.

相对平坦的美国东南部沿海平原，从北卡罗来纳州到德克萨斯州，特别容易受到海平面上升的影响。随着海平面的上升，低洼的沿海淡水森林和高地沼泽之间的分界线向上移。高生产力的森林湿地先后被退化的湿地取代，最终被沿海盐沼取代。咸水入侵不仅改变了植被的组成，高水平的卤化物(称为卤素)可以通过卤化过程与大量的土壤有机物质相互作用，这一过程仍然知之甚少。这些卤化过程很重要，因为它们会产生挥发性的卤代烃，在大气中充当消耗臭氧的化合物。有机质的卤化作用也可能影响有机物的分解速度。这项跨学科的研究将提高我们对氯和溴生物地球化学的理解，并证明卤素在碳循环中的重要性。这项合作研究代表了来自美国东北部、东南部和西部大学的四名不同专业的研究人员之间的新合作。研究生和本科生将有机会在正在进行的地球观察项目中与公民科学家互动，并学习如何向公众传播科学知识。这项研究还将提高人们对海平面上升对美国东南部低洼沿海地区影响的认识。在自然腐殖化过程中，卤素历来被视为惰性元素。然而，最近的大量研究表明，氯和溴是C循环中的活性成分。这项研究的总体目标是评估在高氯和高溴水平的森林湿地中陆地有机物的新的分解过程路线。该研究项目包括实地调查和对照实验，以确定海平面上升对南卡罗来纳州温亚湾沿盐度梯度的碳和卤素生物地球化学循环的影响。卤化臭氧消耗碳化合物和温室气体的通量，以及土壤、凋落物和水中有机氯和有机溴的浓度将沿着盐度横断面和在受控地块内进行量化。研究小组认为，确定土壤和碎屑层中卤化有机物的X射线吸收近边结构(XANES)的新方法，结合使用傅立叶变换离子回旋共振质谱仪(FT-ICR MS)测量水中的卤碳发射和组成，将有助于理解卤素在碳循环中的作用。确定淡水森林湿地、盐碱退化湿地和盐沼湿地空气、土壤和水中卤素的季节变化，代表了海平面上升下滨海湿地的过渡，将有助于从机理和景观上理解海平面上升如何影响滨海湿地陆地有机质的分解、腐殖化和卤化过程。使用不同浓度的氯化物和溴化水的受控野外实验将说明它们在腐殖化和分解过程中的作用。