Assessment of environmental radiological impact in former metallic mines in Extremadura (Spain): A case study

Metal mining in the Extremadura region was very important in the 19th and 20th centuries. However, due to different reasons the great majority of mines ceased operations, leading to plenty of abandoned mining sites, most of them with on-site waste dumps. Although metal extraction is not radioactive per se, it is considered a NORM activity. In this study, three former mining sites, in which Pb-V-Zn-Ag, Pb-Ag, and Pb-Zn were extracted, were selected to assess the radiological impact on the population and the environment. The external γ exposure was estimated by determining the effective dose and elaborating isodose maps of the sites. The presence of the mining sites increased up to 0.41 mSv/y the effective dose over the surrounding background, which is below the reference value of 1 mSv/y. In only one mining site, the uranium and radium activity concentration of waste dumps were higher than the surrounding soil. The soil to plant (wild grass) transfer factors were similar to other reported values without the influence of NORM activities. So, no enhanced transfer of radionuclides was observed. The radiological impact on the environment was assessed by the risk to non-human biota using the tiered approach developed in ERICA Tool. The sum of the risk quotients of all considered radionuclides in the most conservative Tier 1 was below 1. Total dose rates for several terrestrial Reference Animal and Plants (RAPs) were estimated using Tier 3, obtaining values below 40 µGy/h. Therefore, the impact on non-human biota can be considered as negligible.

Ultrasound speed in red deer antlers: a non–invasive correlate of density and a potential index of relative qualit

Deer antlers can be used as an index of individual performance both in ecological and productive contexts. Their quality is often measured only by their biometrical features, such as size, asymmetry or weight. Mechanic characteristics cannot normally be measured without destroying the antler and hence losing the commercial value of the trophies. Here, we studied ultrasonic velocities, density, and tensile strength across various sections of cast antlers of Iberian red deer (Cervus elaphus hispanicus). We found that the speed value depended on the section of the antler and the propagation direction. For antler sections, velocities were lowest for mid–beam and highest for brow tine. Results were similar for density and indirect tensile strength, probably related to differences in functionality among antler sections. Density explained most of the variability of ultrasound–speed. The time elapsed from antler shed affected density more than ultrasound speed. The indirect tensile strength showed a non–linear, decelerating relationship with ultrasound speed. We discuss the applications of ultrasound speed as a non–invasive tool to measure density and physical properties of antlers and antler sections, and their potential use as an index of quality.

Assessment of occupational exposure in a granite quarry and processing factory

Workers in the granite industry face an occupational hazard: silicosis due to the crystalline silica present in inhalable dust. As granite can also present a variable, and occasionally significant, content of naturally occurring radionuclides, they may also face a radiological hazard. In order to assess the risk, a granite industry with a quarry and processing factory was selected to assess the occupational exposure. Three main potential pathways were observed: external irradiation, inhalation of granite dust, and radon exposure. The external dose rate was similar to that in a nearby farming area. A slight increment (0.016-0.076 mSv yr^-1) was observed in the quarry and stockpile, due to quarry faces and granite blocks. The effective dose due to granite dust inhalation was 0.182  ±  0.009 mSv yr^-1 in the worst case scenario (3 mg m^-3 dust load in air and no use of filter masks). Thus, the mean value of the effective dose from these two pathways was 0.26 mSv yr^-1, lower than the reference level of 1 mSv yr^-1 for the general population. The annual mean value of radon concentration in the indoor air was 33 Bq m^-3. However, during granite processing works the radon concentration can increase up to 216 Bq m^-3, due to mechanical operations (sawing, polishing, sanding, etc). This radon concentration was below the 600 Bq m^-3 reference level for action in working places. Therefore, workers in this granite factory face no significant additional radiological exposure, and no-one needs to be designated as occupationally exposed and subject to individual dosimetry.

Assessment of radiological hazard of commercial granites from Extremadura (Spain)

The term "commercial granite" comprises different natural stones with different mineralogical components. In Extremadura, western Spain, "commercial granites" can be classified in three types: granite s.s. (sensus stricti), granodiorite, and diorite. The content of naturally occurring radionuclides depended of the mineralogy. Thus, the (40)K content increased as the relative content of alkaline feldspar increased but decreased as the plagioclase content increased. The radioactive content decreased in the following order: granite s.s. > granodiorite > diorite. In this work, the radiological hazard of these granites as building material was analyzed in terms of external irradiation and radon exposure. External irradiation was estimated based on the "I" index, ranged between 0.073 and 1.36. Therefore, these granites can be use as superficial building materials with no restriction. Radon exposure was estimated using the surface exhalation rates in polished granites. The exhalation rate in granites depends of their superficial finishes (different roughness). For distinct mechanical finishes of granite (polish, diamond sawed, bush-hammered and flamed), the surface exhalation rate increased with the roughness of the finishes. Thermal finish presented the highest exhalation rate, because the high temperatures applied to the granite may increase the number of fissures within it. The exhalation rates in polished granites varied from 0.013 to 10.4 Bq m(-2) h(-1).