Sedimentation and nutrient accumulation: Tracking sources and cycling in waters and sediments

Deb Jaisi, PhD

Professor, Department of Plant and Soil Sciences; Earth Sciences

University of Delaware, USA

Many biogeochemical processes that bring about changes in sediment record normally begin at the sediment-water interface, continue at depth within the sediment column and may persist throughout the lifetime of sediments. Because of the differential reactivity of sedimentary phosphate phases in response to diagenesis, dissolution/precipitation and biological cycling, the oxygen isotope ratios of phosphate (d¹⁸O_P) can carry a distinct signature of these processes, as well as inform on the origin of specific P phases and sedimentary processes. In this work, loading and direction of nutrient flux at the sediment−water interface, and the extent of benthic−pelagic coupling will be discussed. A generalized approach of investigating influx/efflux, relationship with intra- and extra-basinal sources, and sediment-diagenesis identified through water chemistry and advanced characterization methods including X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and X-ray absorption spectroscopy (XAS) will be highlighted. It is anticipated these approaches will catalyze analogous research in both extinct and extant ecosystems and sediments in Nepal.

Date: 5 May 2024 (23 Baisakh 2081)

Time: 13:00-14:00

Venue: Central Department of Geology, Tribhuvan University, Kirtipur

Brief Biography of Professor Deb Jaisi

Dr. Jaisi is a Professor at the Department of Plant and Soil Sciences (joint appointment with Earth Sciences) at the University of Delaware, Newark, DE and co-director of Delaware Environmental Isotope System (EIS) Center- an instrumentation showcase of the university. He received MS in Geology at Tribhuvan University, MS in Geo-environmental Engineering at Asian Institute of Technology, Thailand, and PhD in Geological Sciences at Miami University, USA.

He was an Interdepartmental Bateman Fellow at Yale University in Geology and Geophysics and Chemical Engineering, National Science (NSF) Fellow at the California Institute of Technology (CalTech), visiting professor at Huazhong A. University, and senior visiting fellow at Xiamen University. He is an associate editor in Clays and Clay Minerals, PLOS One, Soil System, and Pedosphere, and editorial board member in ACS Earth and Space Chemistry and Soil Methods.

His honors and awards include Gold medal at Tribhuvan University, Gold (Deeswasmongkul) medal at the Asian Institute of Technology, First Geology Doctoral Award at Miami University, and first Interdepartmental Fellow at Yale. He is a Fellow of International Association of Advanced Materials (IAAM) and NSF. Other recognitions include NSF CAREER, EPSCoR Fellowship, ACS Early Investigator Award, and ORAU Innovation Award. He serves in various regional, national, and international professional organizations and advisory boards and councils in the United States and abroad.

His environmental chemistry research laboratory seeks to better understand phosphorus (P) processes in soils and waters to improve water quality and ecosystem health as well as maintain agricultural sustainability. He has published 103 research papers, book chapters, and edited books. In his professorship career, he has garnered more than $15 million research funds. He has advised 34 graduate students, postdoctoral associates, and visiting scientists from six continents in his research laboratory.