The development of novel terrestrial palaeoclimate proxies based on 3-hydroxy fatty acids

需要从古气候档案中获得广泛的陆地和海洋环境信息，以便更好地了解气候系统，并为预测未来气候变化率、影响和地球系统敏感性提供古气候背景。总体而言，与海洋领域相比，陆地环境受到的关注要少得多，这是因为普遍存在的具有定量古气候作用的生物标志物很少。我们最近发现，在革兰氏阴性细菌膜中合成的3-羟基脂肪酸(3-OH-FA)分布与环境参数之间存在很强的相关性(Wang等人，2016)。基于这一发现，我们定义了重建温度、pH和降水的新的地球化学指标。革兰氏阴性菌的普遍自然分布意味着这些重建过去气候的新技术具有巨大的潜力。我们最近提交了第一篇手稿，证明3-OH-FA生物标志物可以成功地从单个石笋中重建温度和降水信号(Wang等人提交)。这一博士项目将在开发这些生物标志物方面采取下一个令人振奋的步骤：-生产新的全球尺度校准，以扩大和完善新的pH和温度替代指标，并确保被古气候界广泛采用。-新的替代指标首次应用于各种时间尺度(全新世至新生代)上的各种古气候档案(湖泊沉积物、海洋钻探沉积物岩心)。方法：地质工作：收集土壤和沉积物样品，包括温度、水文和各种细菌和植物群落的梯度。新鲜样本将在实地考察中从区域横断面(在美国和欧洲)获得。此外，我们已经从ISRIC土壤库获得了样品，联合主管Griffiths拥有来自英国各地的土壤的冷冻档案，作为全国土壤调查的一部分，以及最近NERC资助的土壤安全计划下的项目(U-GRASS)。实验工作：所有样品都将经过有机地球化学提取和清理和分析方法：即酸解和消化王等人，有机溶剂提取，分离成化学组分，并用GC-FID，GC-MS分析。

A wide range of environmental information from both terrestrial and marine realms is required from palaeoclimate archives to better understand the climate system and to provide a palaeoclimatic context for predictions of future rates of climate change, impact and Earth system sensitivity. Overall, far less attention has been paid to terrestrial environments, compared to the marine realm, due to the paucity of ubiquitous biomarkers with quantitative palaeoclimatic utility. We have recently found strong correlations between 3-hydroxy fatty acid (3-OH-FA) distributions, synthesised within Gram-negative bacterial membranes, and environmental parameters (Wang et al., 2016). Based on this discovery we have defined new geochemical proxies for reconstructing temperature, pH and precipitation. The ubiquitous natural distribution of Gram-negative bacteria means that these new techniques for reconstructing past climate have huge potential.We have recently submitted the first manuscript to demonstrate that 3-OH-FA biomarkers can successfully reconstruct temperature and precipitation signals from an individual stalagmite (Wang et al, submitted). This PhD project will undertake the next exciting steps in the development of these biomarkers: - The production of new global scale calibrations to expand and refine the new proxies for pH and temperature and ensure wide uptake by the palaeoclimate community.- First applications of new proxies to a variety of palaeoclimate archives beyond speleothems (lake sediments, ocean drilling sediment cores) on a variety of time-scales (Holocene to Cenozoic). Methodology: Geological work: Compile a collection of soil and sediment samples which span gradients in temperature, hydrology and a diversity of bacterial and plant communities. Fresh samples will be obtained on field expeditions from regional transects (in the USA and Europe). In addition we have already obtained samples from the ISRIC soil repository and co-supervisor Griffiths possesses a frozen archive of soils from across the UK collected as part of nationwide soil surveys, and a recent NERC funded project (U-GRASS) under the Soil Security Programme.Experimental work: All samples will be subjected to organic geochemical extraction and clean-up and analytical methods: i.e. acid hydrolysis and digestion Wang et al., 2012), extraction with organic solvents, separation into chemical fractions and analysis by GC-FID, GC-MS.