Solid-phase control on the mobility of potentially toxic elements in an abandoned lead/zinc mine tailings impoundment, Taxco, Mexico
Detailed mineralogical and geochemical investigations were conducted within abandoned Pb and Zn flotation tailings at “El Fraile” impoundments in Taxco, Guerrero, central-southern México. These tailings are divided into an active oxidation zone near the surface, an underlying transition zone and an...
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Published in | Applied geochemistry Vol. 22; no. 1; pp. 109 - 127 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
2007
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Detailed mineralogical and geochemical investigations were conducted within abandoned Pb and Zn flotation tailings at “El Fraile” impoundments in Taxco, Guerrero, central-southern México. These tailings are divided into an active oxidation zone near the surface, an underlying transition zone and an unoxidized zone. Although these tailings have undergone 30 a of sulfide oxidation, the active oxidation zone has only penetrated to a depth of 0.2
m in the settling pond, and to 0.6–1.2
m in the dam. The oxidation of sulfide minerals and the insufficiency of pH-buffering minerals have produced low-pH conditions (pH
=
1.9–4.4) and high concentrations of dissolved
SO
4
2
-
, As and heavy metals:
SO
4
2
-
(1534–10086
mg
L
−1), Fe (1.5–2568
mg
L
−1), Zn (36.7–2435
mg
L
−1), Cd (0.4–30.6
mg
L
−1), Pb (<0.01–0.6
mg
L
−1), Cu (0.5–38.2
mg
L
−1) and As (0.01–164
mg
L
−1). These concentrations of dissolved constituents are attenuated by a series of precipitation and sorption reactions. Precipitation of secondary phases, gypsum, goethite, hematite and K-jarosite has led to the formation of cemented layers within the active oxidation zone in the tailings dam. These cemented layers act as a trap for released, potentially toxic elements from the overlying oxidized tailings. Adsorption and coprecipitation on Fe-precipitates play an important role in the mobilization and attenuation of Zn, Cd, Cu and As within the “El Fraile” tailings. Additionally to the well-known ability of Fe-precipitates to strongly trap As and heavy metals, this study shows that precipitation of beudantite (PbFe
3AsO
4SO
4(OH)
6) appears to be one of the solid-phase controls on the natural attenuation of As and Pb and other heavy metals in these tailings. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0883-2927 1872-9134 |
DOI: | 10.1016/j.apgeochem.2006.07.017 |