Chemical data for rock, sediment, biological, precipitate, and water samples from abandoned copper mines in Prince William Sound, Alaska

Abstract

Introduction In the early 20th century, approximately 6 million metric tons of copper ore were mined from numerous deposits located along the shorelines of fjords and islands in Prince William Sound, Alaska. At the Beatson, Ellamar, and Threeman mine sites (fig. 1), rocks containing Fe, Cu, Zn, and Pb sulfide minerals are exposed to chemical weathering in abandoned mine workings and remnant waste piles that extend into the littoral zone. Field investigations in 2003 and 2005 as well as analytical data for rock, sediment, precipitate, water, and biological samples reveal that the oxidation of sulfides at these sites is resulting in the generation of acid mine drainage and the transport of metals into the marine environment (Koski and others, 2008; Stillings and others, 2008). At the Ellamar and Threeman sites, plumes of acidic and metal-enriched water are flowing through beach gravels into the shallow offshore environment. Interstitial water samples collected from beach sediment at Ellamar have low pH levels (to ~3) and high concentrations of metals including iron, copper, zinc, cobalt, lead, and mercury. The abundant precipitation of the iron sulfate mineral jarosite in the Ellamar gravels also signifies a low-pH environment. At the Beatson mine site (the largest copper mine in the region) seeps containing iron-rich microbial precipitates drain into the intertidal zone below mine dumps (Foster and others, 2008). A stream flowing down to the shoreline from underground mine workings at Beatson has near-neutral pH, but elevated levels of zinc, copper, and lead (Stillings and others, 2008). Offshore sediment samples at Beatson are enriched in these metals. Preliminary chemical data for tissue from marine mussels collected near the Ellamar, Threeman, and Beatson sites reveal elevated levels of copper, zinc, and lead compared to tissue in mussels from other locations in Prince William Sound (Koski and others, 2008). Three papers presenting results of this ongoing investigation of sulfide oxidation in Prince William Sound are in press. Koski and others (2008) provide an overview of rock alteration, surface water chemistry, and the distribution of metals at the Ellamar, Threeman, and Beatson mine sites. Based on a 60-day, stream-discharge experiment at Beatson in 2005, Stillings and others (2008) analyze changes in water chemistry during storm events and the flux of metals to the shoreline. Foster and others (2008) investigate the biomass and diversity of microbial communities present in surface waters (streams, seeps, pore waters) using fatty acid methyl ester (FAMES) data and principal component analysis. The publications cited above contain a subset of the total chemical data for rock, sediment, biological, precipitate, and water samples collected from the three mine sites in 2003 and 2005. The purpose of this report is the presentation of complete chemical data sets for all samples collected during the two field periods of fieldwork. Data for a small number of samples collected at two other mines (Schlosser and Fidalgo, fig. 1), visited in 2003, are also included in the tables.