Sulfur Speciation and Stable Isotope Trends of Water-Soluble Sulfates in Mine Tailings Profiles
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- 作者：Bernhard Dold and Jorge E. Spangenberg
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：August 1, 2005
- 年：2005
- 卷：39
- 期：15
- 页码：5650 - 5656
- 全文大小：553K
- 年卷期：v.39,no.15(August 1, 2005)
- ISSN：1520-5851
文摘
Sulfur speciation and the sources of water-soluble sulfatein three oxidizing sulfidic mine tailings impoundmentswere investigated by selective dissolution and stable isotopes.The studied tailings impoundments-Piuquenes, Cauquenes,and Salvador No. 1-formed from the exploitation ofthe Rio Blanco/La Andina, El Teniente, and El SalvadorChilean porphyry copper deposits, which are located inAlpine, Mediterranean, and hyperarid climates, respectively.The water-soluble sulfate may originate from dissolutionof primary ore sulfates (e.g., gypsum, anhydrite, jarosite) orfrom oxidation of sulfide minerals exposed to aerobicconditions during mining activity. With increasing aridityand decreasing pyrite content of the tailings, the sulfurspeciation in the unsaturated oxidation zones showed atrend from dominantly Fe(III) oxyhydroxide fixed sulfate (e.g.,jarosite and schwertmannite) in Piuquenes towardincreasing presence of water-soluble sulfate at Cauquenesand Salvador No. 1. In the saturated primary zones,sulfate is predominantly present in water-soluble form(mainly as anhydrite and/or gypsum). In the unsaturatedzone at Piuquenes and Cauquenes, the 
34SSO4 values rangedfrom +0.5” to +2.0” and from -0.4” to +1.4” ViennaCanyon Diablo Troilite (V-CDT), respectively, indicatinga major sulfate source from pyrite oxidation (34Spyrite =-1.1” and -0.9”). In the saturated zone at Piuquenes andCauquenes, the values ranged from -0.8” to +0.3”and from +2.2” to +3.9”, respectively. At Cauquenesthe 34S enrichment in the saturated zone toward depthindicates the increasing contribution of isotopically heavydissolved sulfate from primary anhydrite (~+10.9”). AtEl Salvador No. 1, the 34SSO4 average value is -0.9”,suggesting dissolution of supergene sulfate minerals (jarosite,alunite, gypsum) with a 34S ~ -0.7” as the mostprobable sulfate source. The gradual decrease of 18OSO4values from the surface to the oxidation front in thetailings impoundments at Piuquenes (from -4.5” to -8.6”Vienna Standard Mean Ocean Water, V-SMOW) and atCauquenes (from -1.3” to -3.5”) indicates the increasingimportance of ferric iron as the main electron acceptorin the oxidation of pyrite. The different 18OSO4 values betweenthe tailings impoundments studied here reflect the localclimates.
34SSO4 values rangedfrom +0.5” to +2.0” and from -0.4” to +1.4” ViennaCanyon Diablo Troilite (V-CDT), respectively, indicatinga major sulfate source from pyrite oxidation (34Spyrite =-1.1” and -0.9”). In the saturated zone at Piuquenes andCauquenes, the values ranged from -0.8” to +0.3”and from +2.2” to +3.9”, respectively. At Cauquenesthe 34S enrichment in the saturated zone toward depthindicates the increasing contribution of isotopically heavydissolved sulfate from primary anhydrite (~+10.9”). AtEl Salvador No. 1, the 34SSO4 average value is -0.9”,suggesting dissolution of supergene sulfate minerals (jarosite,alunite, gypsum) with a 34S ~ -0.7” as the mostprobable sulfate source. The gradual decrease of 18OSO4values from the surface to the oxidation front in thetailings impoundments at Piuquenes (from -4.5” to -8.6”Vienna Standard Mean Ocean Water, V-SMOW) and atCauquenes (from -1.3” to -3.5”) indicates the increasingimportance of ferric iron as the main electron acceptorin the oxidation of pyrite. The different 18OSO4 values betweenthe tailings impoundments studied here reflect the localclimates.