Dr. Yu's research seeks to gain a mechanistic understanding of the biogeochemical nitrogen cycle by investigating how biological, ecological, and hydrological drivers of the nitrogen cycle are recorded and reflected in light stable isotopes (e.g., nitrogen, oxygen, and hydrogen) and how these isotopic imprints can be effectively used to infer and model the sources, transport, and transformation of reactive nitrogen along the terrestrial-aquatic-atmospheric continuum. Research Interests Nitrogen transformations in agricultural soil. Nitrogen sources and cycling in agricultural watersheds. Nitrous oxide emissions from soil and aquatic environments.