Contaminated water, stream sediments and soils close to the abandoned Pinhal do Souto uranium mine, central Portugal

Abstract

The Pinhal do Souto mine exploited a quartz vein containing uranium minerals, mainly autunite and torbernite. This vein intersects a two-mica granite containing 10 ppm U and uraninite. The mine was exploited underground and produced 93,091 kg U 3 O 8 between 1978 and 1989 and was then closed down. Two dumps were left in the mine area and these are partially covered by natural vegetation. Groundwater and surface water have a similar slightly acid-to-alkaline pH. The UO 2 2+ is abundant and complexed with CO 3 2− , under neutral to alkaline pH. Metals and arsenic concentrations in the water increase during the dry season due to the evaporation. Uranium concentration in the water increases (up to 104.42 μg/l) in the wet season, because secondary uranium minerals are dissolved and uranium is released into the water. Soils tend to retain a higher concentration of several metals, including U (up to 336.79 mg/kg) than stream sediments (up to 35.68 mg/kg), because vermiculite from the former could adsorb it more easily than could kaolinite from the latter. The Fe-oxides precipitate retains the highest concentrations of several metals, including U and Th (up to 485.20 and 1053.12 mg/kg, respectively) and the metalloid As, because it is richer in oxyhydroxides and organic matter than stream sediments and soils. The median concentrations of Fe, As, Cd, Pb, Sb, Th, U, W and Zn in soils from this area are higher than in European soils of the FOREGS data. Waters from dry and wet seasons, stream sediments and soils are contaminated and must not be used. This area was compared with another Portuguese abandoned uranium mine area. The former mine caused a lower environmental impact attributable to it having lower sulphide concentration and mineral alteration than in the latter.

Geochemical background of potentially toxic trace elements in reclaimed soils of the abandoned pyrite–uranium mine (south-central Poland)

“…Spatial and temporal distribution of potentially toxic trace elements in soils of the post-mining areas has been a subject of numerous studies (Bačeva et al 2014;Neiva et al 2014;Semhi et al 2014;Kim and Hyun 2015;Wahsha et al 2016). In contrast, limited data exist on geochemical background of trace metal(loid)s in historic mining areas (Loredo et al 2006;Martínez et al 2007;Gałuszka et al 2015;Gutiérrez et al 2016).…”

Natural Gamma Radiation and Uranium Distribution in Soils and Waters in the Agueda River Basin (Spain-Portugal)

“…However, normal U worldwide concentrations in natural waters 1,9 do not exceed 0.4 μg/L, being those samples closest to the mining areas which have higher contents about 10-79.5 μg/l in similar form to other uraniferous areas 10 . Moreover, in a deep borehole hydraulically connected to mineralized quartz-veins (Gallegos de Argañan) the U content is 284 μg/L.…”

Spatio-Temporal Evolution of Sediments Pollution with Mobile Heavy Metals in an Abandoned Mining Area from Romania

“…Also, near abandoned metal mines, high levels of heavy metals can be found as a result of the discharge and dispersion of waste tailings both the aquatic environment and the soils surrounding the mining areas [8][9][10][11][12].…”