Collaborative Research: Identification of Lignin-derived Ligands Associating With Iron

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With support from the Environmental Chemical Sciences Program of the NSF Division of Chemistry, Yu Yang of the University of Nevada, Reno and Rene Boiteau of Oregon State University are studying iron complexes derived from lignin-based organic compounds. Iron oxide-associated organic carbon is one of the largest reservoirs of carbon on the Earth’s surface. Predicting changes to the size of soil carbon reservoirs and sustainably managing soil and water quality is an important challenge. A rigorous understanding of the chemical nature of iron-organic carbon complexes has the potential to assist scientists in this endeavor. So far, the origin and formation mechanism of soil organic carbon in complex with iron remain poorly understood. As a primary precursor for soil organic carbon, plant-derived lignin can be degraded into compounds that may bind to iron oxides. This project aims to uncover the chemical nature of lignin-derived ligands for iron. Soil carbon is an important part of the Earth's carbon cycle, and an element of this cycle that is highly relevant to climate. Graduate, undergraduate, and K-12 students will be engaged in this research at both institutions. Leveraging an NSF-funded Innovations in Graduate Education project, a summer camp module will be developed focusing on environmental chemistry relevant to sustainability, to increase the representation of first-generation students and underrepresented groups in graduate studies in science. This project sets out to develop targeted and non-targeted methods to detect and quantify lignin-derived ligands and their iron complexes by liquid chromatography together with high resolution electrospray ionization mass spectrometry and inductively coupled plasma mass spectrometry. The method will be developed and validated with a set of known lignin degradation products and used to characterize the iron-binding products formed by microbial degradation of lignin in pure culture and soil incubation. It is expected that these studies will help elucidate the chemical nature of biopolymer (lignin)-derived iron ligands and their complexes and provide insights into the chemical mechanisms that fractionate soil organic carbon, ultimately governing soil organic carbon stocks. Such understanding is critical for developing predictive models for the nature and form of soil-constrained organic carbon. The methods developed in this project are expected to be broadly applicable for the investigation of other biopolymer (cellulose, cutin, and others)-derived ligands in soil and aqueous environments.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.