Collaborative Research: The chemistry of lignin's photochemical transformation in the environment: implications for global carbon cycling

在这个由化学系环境化学科学项目资助的项目中，老道明大学的帕特里克·哈彻博士、普林斯顿大学的萨蒂什·梅内尼博士和俄亥俄州立大学的克里斯托弗·哈达德采用了多学科的方法来研究木质素，这是一种沉积在许多植物细胞壁中的复杂有机聚合物，使它们变得坚硬和木质。木质素是一种地球上丰富的有机生物聚合物，为将植物中的碳循环到环境中提供了起点。在这个项目中，研究人员探索了木质素分子重排的途径，以形成存在于土壤、水和沉积物中的分子。一名博士后助理、研究生和几名本科生接受了将地球化学、基础分子研究、高级分析技术和复杂反应路径的现代计算建模相结合的培训。这一培训为这些未来的科学家提供了跨学科的经验。在这个研究项目中，木质素被活性氧物种(ROS)氧化降解，部分重组和聚合形成腐殖质。这些腐殖质可能会有效地隔离木质素衍生的碳，而不是木质素完全氧化为二氧化碳并导致温室气体变暖的理论。本研究模拟环境氧化，研究了合成木质素和天然木质素在铁水存在下的ROS氧化分解过程。该研究采用傅里叶变换离子回旋共振质谱仪、多维液体和固体核磁共振以及基于同步加速器的X射线吸收光谱来识别分子转化途径。这项研究还提供了有关光化学和ROS影响地球大型碳库中陆地碳循环的途径和程度的新信息，影响陆地系统和海洋的化学。

In this project funded by the Environmental Chemical Sciences program of the Chemistry Division, Drs. Patrick Hatcher of Old Dominion University, Satish Myneni of Princeton University, and Christopher Hadad of The Ohio State University employ a multidisciplinary approach to study lignin, a complex organic polymer deposited in the cell walls of many plants, making them rigid and woody. Lignin is an Earth abundant organic biopolymer that provides the starting point to recycle carbon from plants into the environment. In this project, the researchers explore pathways for the molecular rearrangement of lignin to form the molecules present in soil, water and sediments. A postdoctoral associate, graduate students, and several undergraduates are trained to combine geochemistry, fundamental molecular studies, advanced analytical techniques, and modern computational modeling of complex reaction pathways. This training provides these future scientists with an interdisciplinary experience. Undergraduate and high school engagement, including diversified recruitment, is included.In this research project, lignin is subjected to oxidative degradation by reactive oxygen species (ROS) to partially reorganize and polymerize to form humic substances. These humic substances may effectively sequester lignin-derived carbon in contrast to the theory that lignin is completely oxidized to carbon dioxide and contribute to greenhouse warming. This research subjects both synthesized and natural lignin to oxidative decomposition by ROS in the presence of aqueous iron species, mimicking environmental oxidation. The study employs Fourier transform ion cyclotron resonance mass spectrometry, multidimensional liquids and solids NMR, and synchrotron-based X-ray absorption spectroscopy to discern molecular transformation pathways. The research also provides new information regarding both the pathways and magnitude with which photochemistry and ROS affect the cycling of terrestrial carbon among Earth's large reservoirs of carbon, impacting the chemistry of terrestrial systems and oceans.