Science for Decision Making on Uranium Mining in Arizona

Exposure Characterization in Plants and Animals through the Mine Life Cycle

At Kanab North Mine

Kanab North Mine Life Cycle

Kanab north represents conditions during (2016) and after (2018) reclamation.

Vegetation, terrestrial invertebrates, and small rodents were collected for chemical and radiological exposure characterization at

  • Arizona 1 Mine and reference areas in the summer of 2015 (before reclamation ).1
  • Pinenut Mine and reference areas in the summer of 2015 (during active mining).1
  • Pinyon Plain (formerly Canyon) Mine in the summer of 2013 (before mining).2
  • EZ breccia pipes in the summer of 2015 (vegetation only; known uranium-mineralized but undeveloped breccia pipes).
  • Kanab North Mine in 2015 (decades after mining, before reclamation).3


  • We used traditional and new survey tools to understand how mining activities can affect local food webs. Chemicals can enter animals by ingestion, inhalation, absorption, and dietary transfer.1,2,3,4,5,6,7,8
  • Plants and animals take up mining-related radionuclides, uranium, other elements but direct effects were not linked.1,2,3
  • Radiation levels in plants and animals were low. Radiation enters rodents through soil interactions (burrowing, incidental ingestion, bathing, etc.) or their diet. Radium-226 was below protective levels. It is of most concern for rodent health.2,3,8
  • Tadpoles in the mine pond accumulated mining-related chemicals. Arsenic and selenium levels exceed protective thresholds.2

Kanab North Mine Activities

Kanab North Mine is considered a chronic exposure site because of its decades-long postmining, unreclaimed status. Exposure and effects of elements and radioisotopes were anticipated to be greater at the Kanab North Mine than at the Pinyon Plain (formerly Canyon) Mine, a breccia pipe mine where ore has not yet been extracted.

Translocation (movement out of soil into vegetation) of elements and radioisotopes in roots and above-ground vegetation collected from the former mine yard was also evaluated to determine plant species that store elements in the soil and roots, rather than translocating them to the above ground vegetation, as a method of disrupting an exposure pathway for browsers and grazers using the area post reclamation.

Results of this study4, 5 include

  • Chemical and radiological characterization included Al, As, Bi, Cd, Co, Cu, Fe, Pb, Hg, Mo, Ni, Se, Ag, Tl, Th, U, and Zn, gross alpha and beta activities, and U and Th radioisotopes in soil, vegetation (Hesperostipa comata, Artemisia tridentata, Tamarix chinensis), and rodents (Peromyscus maniculatus, P. boylii). Rodent tissues were also analyzed for radium-226 and microscopic lesions.
  • Radioactivities (gross alpha and beta) and some elemental concentrations (e.g., Co, Pb, U) were greater in the Kanab North mine biota than in Pinyon Plain (formerly Canyon) Mine biota, indicating a mining-related elemental signature.
  • Root uptake and translocation occurred for some species and elements. Tamarix chinensis can translocate Pb and Mo from the soil to the leaves. Translocation (including hyperaccumulation), surficial dust loading capability, and soil stabilization should be considered during remediation re-seeding to minimize the dietary uptake and bioaccumulation of mining-related elements by animals consuming vegetation at former mine sites.
  • Mean rodent radium-226 was 3 times greater than expected, indicating radioactive disequilibrium.
  • Lesions associated with metals exposure were also observed more frequently in rodents at Kanab North than those at Pinyon Plain (formerly Canyon) Mine but could not be definitively attributed to U mining.
  • Kanab North biota have taken up U mining-related elements owing to chronic exposure to surficial contamination. However, no literature-based effects thresholds for small rodents were exceeded, and only a few soil and vegetation thresholds for sensitive species were exceeded. Therefore, adverse effects to biota from U mining-related elements at Kanab North are unlikely despite chronic exposure.



Specific Tasks

Task 5a: Compile/evaluate existing and newly collected monitoring data from various agencies/sources
Task 5c: Collect/analyze samples from biota with focus on trust resources
Task 7a: Conduct species surveys
Task 17: Determine biological effects of uranium + trace element mixtures


1 Cleveland, D., Hinck, J.E., Lankton, J.S., 2021, Elemental and radionuclide exposures and uptakes by small rodents, invertebrates, and vegetation at active and post-production uranium mines in the Grand Canyon watershed: Chemosphere, vol. 263,

2 Hinck, J.E., Cleveland, D., Brumbaugh, W.G., Linder, G., and Lankton, J., 2017, Pre-mining trace element and radiation exposure to biota from a breccia pipe uranium mine in the Grand Canyon (Arizona, USA) watershed: Environmental Monitoring and Assessment, February 2017

3 Cleveland, D.M., Hinck, J.E. and Lankton, J.S., 2019, Assessment of chronic low-dose elemental and radiological exposure of biota at the Kanab North uranium mine site in the Grand Canyon watershed: Integrated Environmental Assessment and Management 15:112-125,

4 Hinck, J.E., Linder, G., Darrah, A.J., Drost, C.A., Duniway, M.C., Johnson, M.J., Mendez-Harclerode, F.M., Nowak, E.M., Valdez, E.W., Wolff, S., and van Riper III, C., 2014, Exposure pathways and biological receptors--Baseline data for the Canyon Uranium Mine, Coconino County, Arizona: Journal of Fish and Wildlife Management, v. 5, no. 2, p. 422-440

5 Klymus, K.E., Richter, C.A., Thompson, N., and Hinck, J.E., 2017, Metabarcoding of Environmental DNA Samples to Explore the Use of Uranium Mine Containment Ponds as a Water Source for Wildlife: Diversity 2017, v. 9, no. 4.

6 Valdez, E.W., Hanttula, M.K., and Hinck, J.E. 2021. Seasonal activity and diets of bats at uranium mines and adjacent areas near the Grand Canyon. Western North American Naturalist: Vol. 81 :1-18,

7 Mann, R.K., Duniway, M.C., 2020, Vegetation cover and composition data in environments surrounding uranium mines in the Grand Canyon ecosystem, U.S. Geological Survey data release,

8 Minter, K.M., Jannik, G.T., Hinck, J.E., Cleveland, D., Kubilius, W.P.,and Kuhne, W.W., 2019, Biota dose assessment of small rodents sampled near breccia pipe uranium mines in the Grand Canyon watershed: Health Physics 117:20-27

Kanab North Mine Sources:

4 Cleveland, D.M., Hinck, J.E. and Lankton, J.S., 2019, Assessment of chronic low-dose elemental and radiological exposure of biota at the Kanab North uranium mine site in the Grand Canyon watershed: Integrated Environmental Assessment and Management 15:112-125,

5 Cleveland, D.M., Hinck, J.E. and Lankton, J.S., 2018, Chemical analyses of small rodents, vegetation, and soil collected from the Kanab North breccia pipe uranium mine in the Grand Canyon watershed: U.S. Geological Survey data release,