Titre du document / Document title

Geochemical models of the impact of acidic groundwater and evaporative sulfate salts on Boulder Creek at Iron Mountain, California

Auteur(s) / Author(s)

KEITH David C. ⁽¹⁾ ; RUNNELLS Donald D. ⁽¹⁾ ; ESPOSITO Kenneth J. ⁽¹⁾ ; CHERMAK John A. ⁽¹⁾ ; LEVY David B. ⁽¹⁾ ; HANNULA Steven R. ⁽¹⁾ ; WATTS Malcolm ⁽²⁾ ; HALL Larry ⁽³⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Shepherd Miller, Inc., 3801 Automation Way, Suite 100, Fort Collins, CO 80525, ETATS-UNIS
⁽²⁾ Zeneca. Inc., 3411 Silverside Road, Hanby 1, Wilmington, DE 19897, ETATS-UNIS
⁽³⁾ Zeneca, Inc., 1391 South 49th Street, Richmond, CA 94804, ETATS-UNIS

Résumé / Abstract

During dry season baseflow conditions approximately 20% of the flow in Boulder Creek is comprised of acidic metals-bearing groundwater. Significant amounts of efflorescent salts accumulate around intermittent seeps and surface streams as a result of evaporation of acid rock drainage. Those salts include the Fe-sulfates rhomboclase ((H₃O)Fe³⁺(SO₄)₂.3H₂O), ferricopiapite (Fe₅³⁺(SO₄)₆O(OH).20H₂O), and bilinite (Fe²⁺Fe₂³⁺(SO₄)₄.22H₂O); Al-sulfates-alunogen (Al₂(SO₄)₃.17H₂O) and kalinite (KAl(SO₄)₂.11H₂O); and Ca- and Mg-sulfates - gypsum (CaSO₄.2H₂O), and hexahydrite (MgSO₄.6H₂O). The dissolution of evaporative sulfate salt accumulations during the first major storm of the wet season at Iron Mountain produces a characteristic hydrogeochemical response (so-called rinse-out) in surface waters that is subdued in later storms, Geochemical modeling shows that the solutes from relatively minor amounts of dissolved sulfate salts will maintain the pH of surface streams near 3.0 during a rainstorm. On a weight basis, Fe-sulfate salts are capable of producing more acidity than Al- or Mg-sulfate salts. The primary mechanism for the production of acidity from salts involves the hydrolysis of the dissolved dissolved metals, especially Fe³⁺. In addition to the lowering of pH values and providing dissolved Fe and Al to surface streams, the soluble salts appear to be a significant source of dissolved Cu, Zn, and other metals during the first significant storm of the season.

Revue / Journal Title

Applied geochemistry   ISSN 0883-2927   CODEN APPGEY 

Source / Source

2001, vol. 16, n^o7-8, pp. 947-961 (19 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Oxford, ROYAUME-UNI  (1986) (Revue)

Mots-clés anglais / English Keywords

California ; acidity ; ground water ; contamination ; mining ; models ; evaporites ; sulfates ; metals ; streams ; fluid-rock interaction ; drainage ; pollution ; rhomboclase ; ferricopiapite ; bilinite ; alunogen ; kalinite ; gypsum ; hexahydrite ; dissolution ; precipitation ; surface water ; solutes ; pH ; hydrolysis ; United States ; North America ; chemically precipitated rocks ; sedimentary rocks ;

Mots-clés français / French Keywords

Californie ; Acidité ; Eau souterraine ; Contamination ; Exploitation minière ; Modèle ; Evaporite ; Sulfate ; Elément métallique ; Cours eau ; Interaction fluide roche ; Drainage ; Pollution ; Rhomboclase ; Ferricopiapite ; Bilinite ; Alunogen ; Kalinite ; Gypse ; Hexahydrite ; Dissolution ; Précipitation ; Eau surface ; Soluté ; Mont Iron ; Boulder Creek ; PH ; Hydrolyse ; Etats Unis ; Amérique du Nord ; Roche chimique ; Roche sédimentaire ;

Mots-clés espagnols / Spanish Keywords

California ; Agua subterránea ; Contaminación ; Modelo ; Evaporito ; Sulfato ; Elemento metálico ; Curso agua ; Interacción flúido roca ; Polución ; Romboclasa ; Ferricopiapita ; Bilinita ; Alunógeno ; Kalinita ; Yeso ; Hexahidrita ; Disolución ; Precipitación ; Agua superficie ; Soluto ; pH ; Hidrólisis ; Estados Unidos ; America del norte ; Roca química ; Roca sedimentaria ;

Localisation / Location

INIST-CNRS, Cote INIST : 20984, 35400009506958.0180