Potential toxic elements in stream sediments, soils and waters in an abandoned radium mine (central Portugal).
The Alto da Várzea radium mine (AV) exploited ore and U-bearing minerals, such as autunite and torbernite. The mine was exploited underground from 1911 to 1922, closed in 1946 without restoration, and actually a commercial area is deployed. Stream sediments, soils and water samples were collected between 2008 and 2009. Stream sediments are mainly contaminated in As, Th, U and W, which is related to the AV radium mine. The PTEs, As, Co, Cr, Sr, Th, U, W, Zn, and electrical conductivity reached the highest values in soils collected inside the mine influence. Soils are contaminated with As and U and must not be used for any purpose. Most waters have pH values ranging from 4.3 to 6.8 and are poorly mineralized (EC = 41-186 µS/cm; TDS = 33-172 mg/L). Groundwater contains the highest Cu, Cr and Pb contents. Arsenic occurs predominantly as H2(AsO4)-and H(AsO4)2-. Waters are saturated in goethite, haematite and some of them also in lepidocrocite and ferrihydrite, which adsorbs As (V). Lead is divalent in waters collected during the warm season, being mobile in these waters. Thorium occurs mainly as Th(OH)3(CO3)-, Th(OH)2(CO3) and Th(OH)2(CO3)22-, which increase water Th contents. Uranium occurs predominantly as UO2CO3, but CaUO2(CO3)32-and CaUO2(CO3)3also occur, decreasing its mobility in water. The waters are contaminated in NO2-, Mn, Cu, As, Pb and U and must not be used for human consumption and in agricultural activities. The water contamination is mainly associated with the old radium mine and human activities. A restoration of the mining area with PTE monitoring is necessary to avoid a public hazard.
ICT Centre / University of Minho, Braga, Portugal. imantunes@dct.uminho.pt.|CERENA Centre, Porto, Portugal. imantunes@dct.uminho.pt.
I M H R
IMHR
Antunes
GEOBIOTE Centre, Aveiro, Portugal.|Department of Earth Sciences, University of Coimbra, Coimbra, Portugal.
A M R
AMR
Neiva
CERENA Centre, Porto, Portugal.|Instituto Politécnico de Castelo Branco, Castelo Branco, Portugal.
M T D
MTD
Albuquerque
Department of Earth Sciences, University of Coimbra, Coimbra, Portugal.
P C S
PCS
Carvalho
Department of Earth Sciences, University of Coimbra, Coimbra, Portugal.
A C T
ACT
Santos
MARE - Marine and Environmental Sciences Centre, University of Coimbra, Coimbra, Portugal.
Pedro P
PP
Cunha
D001151:Arsenic / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000737:chemistry*; D008670:Metals / Q000032:analysis; D008906:Mining; D011174:Portugal; D011883:Radium / Q000032:analysis*; D045483:Rivers; D012987:Soil / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D008670:Metals; D012987:Soil; D014875:Water Pollutants, Radioactive; D001151:Arsenic; D011883:Radium
Central Portugal; Contamination; Enrichment factor; Radium mines; Remediation