Donald Sparks, University of Delaware, USA
Recipient of the 2025 Urey Award
DONALD L. SPARKS, S. Hallock du Pont Chair Emeritus and Francis Alison Professor at the University of Delaware, where he has spent his entire 45 year career.  He is internationally recognized for his research in the areas of kinetics of geochemical processes, surface chemistry of natural materials, and impacts of climate change on cycling of metals, carbon, and nutrients in soil and water environments. Dr. Sparks pioneered the application of kinetics to soils, developing methods ranging over a wide time scale and elucidating reaction mechanisms for sorption, desorption, precipitation and dissolution processes.  He was one of the first geoscientists to employ synchrotron radiation to determine sorption mechanisms of  metals and nutrients at the soil mineral/water interface and speciation of metal contaminants in soils. One of the major discoveries made in these studies was that metals such as Ni and Zn could form mixed-metal aluminum hydroxide precipitates (layered double hydroxide phases, LDH) on mineral surfaces and in contaminated field soils. In a myriad of studies spanning over a 20 year period, the kinetics and mechanisms of LDH formation and stability were determined. Using innovative quick X-ray absorption spectroscopy, the Sparks group determined that the LDH phases could occur on minute time scales similar to two-dimensional adsorption processes. Once aging of the LDH phases occur, the metal (e.g., Ni and Zn) becomes sequestered such that its mobility and bioavailability is significantly diminished. Over the past 15 years, Dr. Sparks’ research has focused on the impacts of climate change e.g., flooding, sea level rise, and salinity on carbon complexation with minerals and cycling of toxic metal(loid)s and nutrients in the Earth’s Critical Zone. Synchrotron-based tools (STXM- NEXAFS) were used to determine associations of carbon with other elements in soils and carbon speciation. Additional studies used FT-ICR-MS to determine the temporal molecular fractionation of dissolved organic matter on iron hydroxide surfaces.
Dr. Sparks is the author of three textbooks, 12 edited books, and 370 refereed papers and book chapters.  He is a fellow of five scientific societies, including the Geochemical Society and the European Association of Geochemistry and he has been the recipient of major awards and lectureships including the Geochemistry Medal from the American Chemical Society, the Liebig Medal from the International Union of Soil Sciences,  Pioneer in Clay Science award from the Clay Minerals Society, an Einstein Professorship from the Chinese Academy of Sciences, the Soil Science Research Award from the Soil Science Society of America, the Environmental Quality Award from the American Society of Agronomy, and the Philippe Duchaufour Medal from the European Geosciences Union. Dr. Sparks was the recipient of the Alison Award, the highest faculty award, and an Honorary Doctor of Science Degree from the University of Delaware. One of the highlights of his career has been the mentoring of 65 graduate students and 35 postdoctoral researchers. Dr. Sparks served as president of the Soil Science Society of America and the International Union of Soil Sciences and as chair of the U.S. National Academy of Sciences (NAS) Committee for Soil Sciences.