Geochemical, Biological and Economic Effects of Arsenic and Other Oxyanions on a Mining Impacted WatershedEPA Grant Number: R825289
Title: Geochemical, Biological and Economic Effects of Arsenic and Other Oxyanions on a Mining Impacted Watershed
Investigators: Miller, Glenn C. , Anderson, Susan L. , Hershey, Ron , Miller, Watkins W. , Papelis, Lambis , Shaw, Douglass , Tyler, Scott
Institution: University of Nevada - Reno , Desert Research Institute
Current Institution: University of Nevada - Reno , Bodega Marine Laboratory , University of California - Davis
EPA Project Officer: Hiscock, Michael
Project Period: January 1, 1997 through December 31, 1999 (Extended to December 31, 2000)
Project Amount: $767,805
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Water and Watersheds , Water
Description:Precious metals mining in the arid western United States has increased substantially in the previous decade, primarily due to modern methods of cyanide-based extraction of ore. Because arsenic (As) is often associated with gold deposits, release of As in soils and surface waters has become an increasing concern. This proposed research will focus on the geochemical, biological and economic impacts of As released during mining in the Humboldt River watershed in northern Nevada. Mines in this watershed produced 4.9 million ounces of gold in 1994, which was nearly half of the nation's production of gold in that year. The mining techniques are of relatively recent origin, and the scale of these mines has generated contaminant release issues which are not well understood.
Arsenic and other contaminants are released during normal mining practices when mineralized rock is crushed and exposed to oxygen and water. Pit wall rock, waste rock dumps and spent heaps are all potential sources of As. In addition, many of the large pits created in this watershed penetrate groundwater and, when mining and the associated dewatering activities are discontinued, will result in large lakes as the groundwater tables begin to recover. Since most of the larger future pit lakes are still being mined, the ultimate water quality in the pit lakes is unknown, and the policy implications related to the biological and economic impact of those pit lakes are equally unknown.
The geochemical investigations will focus on models used to predict precious metals pit lake water quality, particularly with respect to As sorption on metal oxides (DRI project). Investigations proposed will examine both As sorption by precipitates in present pit lakes and factors which influence As release as a function of wall rock-water interactions. A second geochemical focus will be to understand the hydrologic and geochemical release of constituents from heaps, focusing on prediction of As discharge from the base of the heaps (UNR project). Because As sorption is dependent on both the pH of the solution and surface mineralogy, methods to predict As discharge from these heaps are required for long-term management. Using both column studies and actual decommissioned heaps, we will couple hydrologic and geochemical models in order to better understand these systems.
The biological investigations of arsenic (LBL project) will focus on the genotoxic and developmental response of a variety of organisms to mine-impacted water, particularly pit lakes. These data are necessary to better understand whether the lakes can be used as wildlife habitat or if they present a significant risk to native or introduced species.
Because the extent of mining in the Humboldt River watershed has the potential to affect long-term economic use of water, we will also investigate how water quality (with an emphasis on As) and water quantity will affect recreational and agricultural uses of the Humboldt River watershed (UNR project). These studies will examine the present uses of water in the Humboldt River watershed, and how that water will be affected by changes resulting from present and future mining.