Collaborative Research: Identifying basin-specific controls on isotopic and chronological offsets of lake sediment leaf wax hydrogen isotope records

合作研究：确定对湖泊沉积物叶蜡氢同位素记录的同位素和年代偏移的流域特定控制

• 批准号: 1636740
• 负责人: Aaron Diefendorf
• 金额: $ 22.26万
• 依托单位: University of Cincinnati Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1636740&HistoricalAwards=false
• 关键词: Collaborative; Research; Identifying; basin; specific

To determine how future precipitation might change, it is important to have a baseline of how precipitation changed in the past. However, determining past precipitation, prior to the generation of instrumental records, has remained challenging and necessitates the use of precipitation proxies that are preserved in the geologic record. Biological proxies, such as leaf waxes, hold promise in this regard as the hydrogen isotopic composition of leaf wax primarily reflects that of precipitation. Therefore, leaf waxes preserved in lake sediments are a potential source of high resolution information about how precipitation and the water cycle have changed over geologic time. However, the transfer of modern leaf waxes to lake sediments appears to introduce offsets in hydrogen isotope values. This project will help define these offsets and identify the factors that control them, thus allowing for improved reconstructions of past hydrological conditions. Until these offsets are evaluated, and their influence measured, the quantitative link between sedimentary leaf wax and precipitation will remain limited. Identification of these factors will allow selection of lakes where the effects of these offsets are minimal. This is critical for constraining past changes in hydrology prior to the instrumental record and will help anticipate future hydrologic change. This project will benefit society by creating educational and research experiences for undergraduates through interdisciplinary collaborations with St. Lawrence University, a primarily undergraduate institution. This will improve STEM field retention by providing research and training experiences for undergraduate students to develop advanced research skill sets, expand scientific understanding, and strengthen preparation for graduate studies or a career in the geosciences. Finally, this research will promote a broader public understanding of the geosciences and appreciation of scientific research by expanding on museum exhibits in collaboration with the Cincinnati Museum Center, a large urban cultural institution.Past precipitation remains a challenge to quantify. Biological proxies, such as leaf waxes, hold promise in this regard as the hydrogen isotopic composition of leaf wax primarily reflects plant source water (i.e., precipitation). However, quantitative paleohydrology, as inferred from precipitation hydrogen isotopic composition, is limited by a poor understanding of the taphonomic processes governing the source, integration, and transport of leaf waxes from plants to sediments. This project will address two significant gaps in our understanding of lake sediment leaf waxes. First, the investigators will determine how vegetation proximity influences leaf wax hydrogen isotope signals in lake sediments. Second, they will determine how important reworking of older leaf waxes via fluvial erosion impacts the apparent age of leaf waxes in lake sediments. This project examines these two processes in temperate lakes in the Adirondack Mountains, NY, USA. Research methods will include forest inventorying, modern leaf wax (n-alkane and n-alkanoic acid) molecular and isotope (hydrogen, carbon) characterization, lake sediment coring and dating (210Pb, 137Cs, 14C), and compound-specific radiocarbonanalyses of n-alkanes in lake sediments, catchment soils, and fluvial suspended sediments. The project will benefit society by 1) establishing partnerships with St. Lawrence University, a primarily undergraduate institution, to develop interdisciplinary collaborations and undergraduate research opportunities, create graduate student mentoring opportunities, and provide a hands-on isotope workshop for undergraduates; 2) improving STEM field retention by providing research and training experiences for two undergraduate students per year to develop advanced research skill sets, expand scientific understanding, and strengthen preparation for graduate studies or a career in the geosciences; 3) increasing the number of women in STEM fields by support of a Ph.D. student and an undergraduate students; 4) providing mentoring to enhance the educational and career development of undergraduate and graduate students, and improving the success of mentoring approaches through regular assessment and professional development; and 5) promoting broader public understanding of the geosciences and appreciation of scientific research by expanding on museum exhibits in collaboration with the Cincinnati Museum of Center, a large urban cultural institution.

要确定未来的降水量可能如何变化，重要的是要对过去的降水量如何变化有一个基线。然而，在生成仪器记录之前确定过去的降雨量仍然具有挑战性，因此必须使用保存在地质记录中的降雨量指标。生物替代品，如叶蜡，在这方面很有希望，因为叶蜡的氢同位素组成主要反映降水的氢同位素组成。因此，保存在湖泊沉积物中的叶蜡是关于降水和水循环如何随着地质时间的变化而变化的高分辨率信息的潜在来源。然而，现代树叶蜡向湖泊沉积物的转移似乎带来了氢同位素值的偏移。该项目将帮助确定这些偏移量并确定控制它们的因素，从而改进对过去水文状况的重建。在对这些偏移量进行评估并测量其影响之前，沉积叶蜡和降水之间的定量联系仍将是有限的。识别这些因素将允许选择这些偏移量影响最小的湖泊。这对于在仪器记录之前限制水文学过去的变化是至关重要的，并将有助于预测未来的水文学变化。该项目将通过与圣劳伦斯大学的跨学科合作，为本科生创造教育和研究经验，从而造福社会。圣劳伦斯大学主要是一所本科院校。这将通过为本科生提供研究和培训经验来提高STEM现场留存率，以发展高级研究技能，扩大科学理解，并加强研究生学习或在地球科学领域的职业准备。最后，这项研究将通过与大型城市文化机构辛辛那提博物馆中心合作扩大博物馆展品，促进更广泛的公众对地球科学的理解和对科学研究的欣赏。过去的降水仍然是一个量化的挑战。生物替代品，如叶蜡，在这方面很有希望，因为叶蜡的氢同位素组成主要反映植物源水(即降水)。然而，从降水氢同位素组成推断的定量古水文学，由于对控制叶蜡从植物到沉积物的来源、整合和运输的攻丝过程缺乏了解而受到限制。这个项目将解决我们对湖泊沉积物叶蜡理解中的两个重大空白。首先，研究人员将确定植被的接近程度如何影响湖泊沉积物中的叶蜡氢同位素信号。其次，他们将确定通过河流侵蚀重新加工较老的叶蜡对湖泊沉积物中叶蜡的表观年龄有多大影响。这个项目研究了美国纽约州阿迪朗达克山脉温带湖泊中的这两个过程。研究方法将包括森林清点、现代叶蜡(正构烷烃和正构烷酸)分子和同位素(氢、碳)表征、湖泊沉积物取心和测年(210Pb、137Cs、14C)，以及湖泊沉积物、集水区土壤和河流悬浮沉积物中正构烷烃的特定化合物放射性碳分析。该项目将通过以下方式造福社会：1)与以本科生为主的圣劳伦斯大学建立伙伴关系，以发展跨学科合作和本科生研究机会，创造研究生指导机会，并为本科生提供亲身实践的同位素研讨会；2)通过每年为两名本科生提供研究和培训经验，提高STEM领域的留存率，以发展高级研究技能，扩大科学理解，并加强对研究生学习或地球科学职业生涯的准备；3)通过支持一名博士和一名本科生，增加STEM领域的女性人数；4)提供指导，以促进本科生和研究生的教育和职业发展，并通过定期评估和专业发展改进指导方法的成功；以及5)通过与大型城市文化机构辛辛那提中心博物馆合作，扩大博物馆展品，促进更广泛的公众对地球科学的了解和对科学研究的欣赏。

项目成果

Centennial-scale age offsets of plant wax n-alkanes in Adirondack lake sediments

阿迪朗达克湖沉积物中植物蜡正烷烃的百年尺度年龄偏移

• DOI: 10.1016/j.gca.2021.02.022
• 发表时间: 2021
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Freimuth, Erika J.;Diefendorf, Aaron F.;Lowell, Thomas V.;Schartman, Anna K.;Landis, Joshua D.;Stewart, Alexander K.;Bates, Benjamin R.
• 通讯作者: Bates, Benjamin R.

Sedimentary n-alkanes and n-alkanoic acids in a temperate bog are biased toward woody plants

• DOI: 10.1016/j.orggeochem.2019.01.006
• 发表时间: 2019-02
• 期刊: Organic Geochemistry
• 影响因子: 3
• 作者: E. Freimuth;A. Diefendorf;T. Lowell;G. Wiles

Stable source of Holocene spring precipitation recorded in leaf wax hydrogen-isotope ratios from two New York lakes

• DOI: 10.1016/j.quascirev.2020.106357
• 发表时间: 2020-07
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Anna K. Schartman;A. Diefendorf;T. Lowell;E. Freimuth;A. Stewart;J. Landis;Benjamin R. Bates