Prof. Johnson's group focuses on environmental geochemistry, isotope geochemistry, and hydrogeology. The group is working to better understand several redox-sensitive contaminant elements, including chromium, selenium, uranium, and mercury. They develop and use methods for measurement of the stable isotopes of these and other elements as indicators of key geochemical reactions, contamination sources, and past environments on Earth.
The group uses the department's multicollector ICP-MS laboratory constantly to make these measurements and often develops or improves measurement methods.
Ph.D., University of California at Berkeley
- GEOL 117: The Oceans
- GEOL 118: Natural Disasters
- GEOL 370/GEOG 370/ESE 320: Water Planet/Water Crisis
- GEOL 470: Hydrogeology
- GEOL 562: Isotope Geochemistry
- GEOL 579: Isotope Hydrogeology
Additional Campus Affiliations
Lu, Z., Zhu, J. M., Tan, D., Johnson, T. M., & Wang, X. (2023). Double Spike-Standard Addition Technique and Its Application in Measuring Isotopes. Analytical Chemistry, 95(4), 2253-2259. https://doi.org/10.1021/acs.analchem.2c03802
Basu, A., Schilling, K., Halliday, A. N., Wasserman, N., & Johnson, T. M. (2022). Te(IV) immobilization by siderite: Reaction kinetics, mechanism, and Te isotopic fractionation. Chemical Geology, 612, Article 121123. https://doi.org/10.1016/j.chemgeo.2022.121123
Dwivedi, P., Schilling, K., Wasserman, N., Johnson, T. M., & Pallud, C. (2022). Oxidation of Dissolved Tetravalent Selenium by Birnessite: Se Isotope Fractionation and the Effects of pH and Birnessite Structure. Frontiers in Earth Science, 10, Article 909900. https://doi.org/10.3389/feart.2022.909900
Johnson, T. M., Druhan, J. L., Basu, A., Jemison, N. E., Wang, X., Schilling, K., & Wasserman, N. L. (2022). A review of the development of cr, se, u, sb, and te isotopes as indicators of redox reactions, contaminant fate, and contaminant transport in aqueous systems. In Isotopic Constraints on Earth System Processes (pp. 237-269). Wiley. https://doi.org/10.1002/9781119595007.ch10
Vengosh, A., Coyte, R. M., Podgorski, J., & Johnson, T. M. (2022). A critical review on the occurrence and distribution of the uranium- and thorium-decay nuclides and their effect on the quality of groundwater. Science of the Total Environment, 808, Article 151914. https://doi.org/10.1016/j.scitotenv.2021.151914