Stable Isotope Approaches in Vadose Zone Research

Recent developments in the measurement, modeling, and application of stable isotope tools to provide insights on water flow, transport, biogeochemical, and ecological processes in the vadose zone have motivated a special section in . We give an overview of recent advances and challenges in stable isotope approaches in the vadose zone and present the key findings from the five manuscripts in this special section. These five manuscripts advance our understanding of (i) analytical developments in water stable isotope analysis, (ii) modeling of water and transport within the soil matrix using water stable isotopes, and (iii) using compound-specific isotope analysis for identifying the fate of nonaqueous-phase liquids in the unsaturated zone