Arsenic speciation at the Lucky Shot Gold Mine, Alaska.

Torrance, Keith and Keenan, Helen and Hagedorn, Birgit and Munk, LeeAnn (2011) Arsenic speciation at the Lucky Shot Gold Mine, Alaska. In: International Conference on Environmental Geology and Health SEGH 2011, 2011-04-11 - 2011-04-14. (Unpublished)

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Abstract

Historical gold mining in Alaska has created a legacy of abandoned mine shafts and tailings, which continues to impact surface water quality. The Lucky Shot gold mine in Hatcher’s Pass, South-central Alaska, operated from 1918 until 1942, working gold-bearing quartz veins within a Cretaceous tonalite intrusion by means of horizontal adits tunnelled into the hillside. Arsenopyrite present in the quartz veins contributes to elevated arsenic levels in water draining from the adit; up to 700 µg L-1 or roughly seventy times the United States Enviromental Protection Agency Drinking Water Standard of 10 µg L-1. This prospect is being assessed for re-opening, based on the high price of gold, currently around $1,400 per ounce, and subject to environmental permitting. Water samples were collected from streams, adits and boreholes around the mine and analyzed for major and minor elements using ion-chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS). Arsenic speciation was performed in the field to determine the ratio of As(III)/As(V) using anion-exchange chromatography, following the method developed by Wilkie and Hering (1998). It was determined that in the vicinity of the adits, surface water had elevated pH’s and displayed no characteristics of acid mine drainage. Despite being well-oxygenated, As(III) was the dominant arsenic species in the adit water. Oxygen isotope studies support the view that the predominance of As(III) can be attributed to the low residence time of water in the system, preventing thermodynamical equilibrium being attained.

ORCID iDs

Torrance, Keith ORCID logoORCID: https://orcid.org/0000-0002-2396-6575, Keenan, Helen ORCID logoORCID: https://orcid.org/0000-0003-0970-5392, Hagedorn, Birgit and Munk, LeeAnn;
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