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Critical Zone (CZ) scientists have advanced understanding of Earth's surface through process‐based research that quantifies water, energy, and mass fluxes in predominantly undisturbed systems. However, the CZ is being increasingly altered by humans through climate and land use change. Expanding the scope of CZ science to include both human‐ and non‐human controls on the CZ is important for understanding anthropogenic impacts to Earth's surface processes and ecosystem services. Here, we share perspectives from predominantly U.S.‐based, early career CZ scientists centered around broadening the scope of CZ science to focus on societally relevant science through a transdisciplinary science framework. We call for increased training on transdisciplinary methods and collaboration opportunities across disciplines and with stakeholders to foster a scientific community that values transdisciplinary science alongside physical science. Here, we build on existing transdisciplinary research frameworks by highlighting the need for institutional support to include and educate graduate students throughout the research processes. We also call for graduate‐student‐led initiatives to increase their own exposure to transdisciplinary science through activities such as transdisciplinary‐focused seminars and symposiums, volunteering with local conservation groups, and participating in internships outside academia. Plain Language Summary Critical Zone (CZ) science focuses on understanding the surface of the Earth. This zone stores and transfers water and nutrients that are vital to life for flora, fauna, and humans. However, processes that control water and nutrients in the CZ are evolving under increased human and climate pressures. Asking questions about how humans alter, and are impacted by, changes to the CZ has potential to advance CZ science and benefit society. A significant portion of CZ science is conducted by graduate students who are often not trained to do transdisciplinary research. For a sustained shift toward societally relevant CZ research, increased training and collaboration should occur at the graduate student level. In this commentary, we synthesize perspectives from early career CZ scientists to share an idealized vision for the future of CZ science and ideas for improving graduate student training. Key Points Transdisciplinary science provides a framework for Critical Zone science to broaden toward environmental problems that impact humans Graduate students need transdisciplinary training to facilitate a sustained shift toward societally relevant Critical Zone research Graduate students can also take individual initiative to facilitate learning and engagement with transdisciplinary literature and research

This study integrates geochemical modeling, spatial analysis and several statistical methods including principal component analysis, multivariate regression and cluster analysis to investigate hydrogeologic controls of arsenic and uranium contamination within groundwater of the Arikaree aquifer on the Pine Ridge Reservation (PRR). Located in southwestern South Dakota, geologic strata on the PRR are enriched with uranium and arsenic due to volcanic ash deposits emplaced into the White River Group, which unconformably underlies the Arikaree Group. Groundwater samples were obtained for over 250 wellbores through collaboration with the Oglala Sioux Tribe and Indian Health Service. Cluster analysis was used to delineate differences in groundwater chemistry in these data, and spatial analysis identified four regions, which represent upgradient, intermediate, and downgradient portions of the Arikaree aquifer. Groundwater alkalinity, sodium, and pH levels increase along flowpaths in the Arikaree aquifer despite rising carbonate mineral saturation indices, indicating that volcanic ash may act as a secondary source of alkalinity in the aquifer. Elevated alkalinity and pH levels are the primary measured drivers of arsenic and uranium mobility within the Arikaree aquifer, indicating that downgradient sections of the aquifer in the northern portions of the PRR are most likely to face impacts from groundwater contamination.