Hydrology and geochemistry of aquifer and stream contamination related to acidic water in Pinal Creek basin near Globe, Arizona

Abstract

iron-oxide minerals to precipitate on the streambed. Although trace metals, such as copper, nickel, The Final Creek Basin in central Arizona has zinc, and lead, are more concentrated on iron been an area of large-scale copper mining for more oxides than manganese oxides, trace-metal than 100 years. Contamination sources, mainly sorption to manganese oxides is more important impoundments of water related to mining, because manganese oxides are much more generally were acidic. A manmade lake formed in abundant than iron oxides in the streambed. 1941 and drained in 1988 probably was the single Research at the Final Creek toxic site was largest source of contamination. Concentrations of funded mainly by the U.S. Geological Survey's dissolved iron and sulfate in the lake were greater Toxic Substances Hydrology Program and has than 2,000 and 13,000 milligrams per liter, been ongoing since 1984. Focus of the study respectively. Acidic water from this lake and included the acidic plume and areas affected by other mining-related sources has generated a neutralized water. A combination of column and 15-kilometer-long plume of acidic ground water in other laboratory experiments and computer the alluvial aquifer. Contaminated ground water simulations characterized oxidation-reduction, is neutralized mainly by calcite dissolution as it neutralization, and sorption reactions that moves through the alluvium and the shallow basin evidently occur in the core of the plume. Solidfill. Acid-base, oxidation-reduction, and sorption phase associations of copper, manganese, reactions accompany the neutralization of acidic zinc, calcium, aluminum, and sulfate in the ground water. Oxidation-reduction reactions subsurface were determined through the use involve principally iron and manganese. Sorption of sequential extractions. Field sampling and of oxidized precipitates controls the distribution of laboratory work identified oxide precipitates, cobalt, copper, and nickel. These metals and other associated trace metals, and trends in water trace metals are near detection limits in neutralized chemistry in the area of perennial flow, ground water. Neutralized ground water, which had a pH of iMTRoni irriON 6.1 in 1990, discharges to the land surface to form N1 "°DUUTION a reach of perennial flow in Final Creek.