Seasonal variations of Zn/Cu ratios in acid mine water from Iron Mountain, California

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Time-series data on Zn/Cu weight ratios from portal effluent compositions [(Zn/Cu)water] at Iron Mountain, California, show seasonal variations that can be related to the precipitation and dissolution of melanterite [(FeII,Zn,Cu)SO4·7H2O]. Mine water and actively forming melanterite were collected from underground mine workings and chemically analyzed. The temperature-dependent solubility of Zn-Cu-bearing melanterite solid solutions was investigated by heating-cooling experiments using the mine water. Rapid kinetics of melanterite dissolution and precipitation facilitated reversed solubility experiments at 25°C. Non-reversed solubility data were obtained in the laboratory at 4° and 35°C and at ambient underground mine conditions (38° and 42°C). Copper is partitioned preferentially to zinc into melanterite solid solutions at all temperatures investigated. During the annual dry season, values of (Zn/Cu)water in the Richmond portal effluent increase to values between 8 to 13, consistent with formation of melanterite during this period. During the annual wet season, the onset of high discharge from the mine portals is characterized by a significant decrease in (Zn/Cu)water to values as low as 2. This phenomenon may be caused by dissolution of melanterite with values of (Zn/Cu)solid ranging from 1.5 to 3.5.

Publication type Book chapter
Publication Subtype Book Chapter
Title Seasonal variations of Zn/Cu ratios in acid mine water from Iron Mountain, California
ISBN 9780841227729
DOI 10.1021/bk-1994-0550.ch022
Volume 550
Year Published 1993
Language English
Publisher American Chemistry Society
Contributing office(s) California Water Science Center
Description 21 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Environmental geochemistry of sulfide oxidation
First page 324
Last page 344
Country United States
State California
City Iron Mountain
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