EAR-PF Salinity Influence on Methane Emissions from Tidal Wetlands Determined by Clumped Isotopes

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。甲烷（CH4）是地球大气中含量最多的有机气体，也是一种温室气体。美国环保署估计，甲烷占全国温室气体排放量的10% （www.epa.gov/ghgemissions）。向大气排放的甲烷包括人为和自然两种来源。其中，湿地不仅在全球甲烷收支中发挥着重要作用，而且也是相关不确定性最大的来源之一。该提案的重点是切萨皮克湾地区的湿地甲烷排放。该地区由多种产生甲烷的环境组成，最著名的是淡水潮汐湿地。拟议的研究将有助于表征由河口盐度的自然和人为强迫驱动的区域甲烷收支和微生物过程的作用。这项工作将支持一个长期项目，即建立一个区域甲烷循环模型，并对世界这一地区的大气甲烷进行建模。了解大气甲烷收支的演变对当地潮汐湿地恢复项目和国家气候变化政策决策具有重要意义。对潮汐湿地甲烷排放的估计具有高度的不确定性，而且通常受到缺乏信息的影响，但这对于确定大气甲烷预算及其随时间的变化至关重要。本研究将采用新的甲烷同位素指纹图谱方法，评估盐度（季节和区域变化）对马里兰州湿地微生物甲烷产量和消耗的影响。本工作将记录依赖于不同环境条件的团块同位素中碳和氢的特征，并寻求开发一种同位素示踪剂来跟踪不同潮汐湿地系统中受环境因素影响的微生物甲烷生产和消耗速率。双取代甲烷同位素（团块同位素）为解决盐度和电子受体变化等不同环境条件下生物甲烷形成途径的不确定性提供了另一种方法。本研究还将解决潮汐湿地系统中微生物在不同盐度影响下产生和消耗甲烷的途径的关键问题。这项工作结合了原位甲烷测量和实验室（在受控条件下）实验。本研究的结果将提高我们对马里兰州潮汐湿地在甲烷收支中的作用的理解，并将有利于环境政策的制定。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Methane (CH4) is the most abundant organic gas in Earth’s atmosphere, and a greenhouse gas. The EPA estimates indicate that methane accounts for 10% of national greenhouse gas emissions (www.epa.gov/ghgemissions). Methane emissions to the atmosphere include both anthropogenic and natural sources. Of these, wetlands not only play a significant role in the global methane budget, but are also one of the sources with the greatest associated uncertainties. This proposal focuses on wetland methane emissions within the Chesapeake Bay region. This region consists of a variety of environments that produce methane, most notably freshwater tidal wetlands. The proposed research will help characterize the regional methane budget and role of microbial processes that are driven by both natural and anthropogenic forcing of estuarine salinity. This work will support a longer-term project to construct a regional methane cycle model and to model atmospheric methane in this part of the world. Understanding the evolution of the atmospheric methane budget has important implications for local tidal wetlands restoration projects and national climate change policy decisions.Estimates of methane emissions from tidal wetlands are subject to high uncertainty and commonly suffer from the lack of information, but essential for determining the atmospheric methane budget and its change over time. The proposed research will evaluate the role of salinity (seasonal and regional changes) on microbial methane production and consumption in Maryland wetlands using new methane isotopologue fingerprinting approach. This work will document signatures of carbon and hydrogen in clumped isotopes that depend on varying environmental conditions and seek to develop an isotopologue tracer to track rates of microbial methane production and consumption influenced by environmental factors in different tidal wetlands systems. Using doubly substituted methane isotopologues (clumped isotopes) offers an additional way to resolve uncertainties about the biogenic methane formation pathways under various environmental conditions including the salinity and electron acceptors variability. This study will also address key questions regarding the pathways in methane production and consumption by microbes under the influence of various salinity regimes in tidal wetland systems. The work is a combination of in-situ methane measurements and laboratory (under controlled conditions) experiments. The results of this study will improve our understanding of the role of tidal wetlands in methane budget in Maryland and will be beneficial in environmental policy decisions.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.