Prof. Johnson's research group works in environmental geology, and most current work investigates the fate and transport of redox-sensitive contaminants. The mobility and toxicity of many contaminants depends very strongly on oxidation and reduction reactions
The group applies stable isotope measurements toward detecting and quantifying these reactions in groundwater and surface water settings. Isotope geochemistry provides us with an advanced set of tools, some of which we have developed, or are developing, ourselves.
Isotope geochemistry is the study of small, but quite measureable differences in the abundance of various stable and natural radioactive elements in geological materials. The resulting tools are challenging in their use, but can provide unique information of great use in environmental studies. Our group works at the forefront of research in this rapidly developing area.
One of the frontiers in isotope geochemistry lies in developing and applying measurements of isotope ratios in elements heavier than sulfur. These "heavy stable isotope" measurements will be applied in many areas of geoscience; our current focus is mosty on the environment, but we also appy these measurements in studies of marine sediments.