Natural and anthropogenic processes affecting radon releases during mining and early stage reclamation activities, Pinenut uranium mine, Arizona, USA

Radon (Rn-air) was monitored in open air in publicly accessible areas surrounding the Pinenut uranium (U) mine during mining and reclamation activities in 2015-16 to address concerns about mining related effects to areas surrounding Grand Canyon National Park (GCNP) in Arizona, USA. During July 2015, Rn-air concentrations associated with the ore storage pile monitoring site were larger than those at the mine vent monitoring site and likely resulted from the relatively large amount of ore stored on site during this period. Higher wind velocities at the ore pile monitoring site generally resulted in lower Rn-air concentrations; however, wind velocity did not appear to be an important factor in controlling Rn-air concentrations at the mine vent monitoring site. Physical disturbances of the ore pile by heavy equipment did not coincide with elevated Rn-air concentrations at the ore storage pile or mine vent monitoring sites. The relative size of the ore storage pile showed a positive trend with the daily mean Rn-air concentration measured at the ore pile monitoring site. Principal component analysis (PCA) was applied to the ore pile and mine vent multivariate data sets for simultaneous comparison of all measured variables during 230 days of the study period. A significant positive coefficient for Rn-air was associated with a significant negative coefficient for wind speed for principal component (PC) 2(ore pile). Significant, positive PC2(mine vent) coefficients included Rn-air, wind direction, and relative ore pile size indicating that Rn-air variations at the mine vent monitoring site may be affected by Rn sourced from the ore pile. The ore pile is located about 200 m south of the mine vent Rn monitor with the prevalent wind direction coming from the south. All data generated during the field study and laboratory verification tests were published by Naftz et al. (2018) and are available online at: https://doi.org/10.5066/F79Z946T.