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Charles N. Alpers

Publications and source records attributed to Charles N. Alpers.

At least 109 records · Page 6Linked to original sources
USGS2000

Metal exposure in a benthic macroinvertebrate, Hydropsyche californica, related to mine drainage in the Sacramento River

A biomonitoring technique was employed to complement studies of metal transport in the upper Sacramento River affected by acid mine drainage. Metals (Al, Cd, Cu, Fe, Hg, Pb, and Zn) were determined in a resident invertebrate, Hydropsyche californica (Insecta: Trichoptera), and streambed sediments (<62 µm) to assess metal contamination within a 111-km section of the river downstream of the mining area. Metals in H. californica also were interpreted to be broadly indicative of metal exposure in fish. Total Hg was determined in the whole body of the insect, whereas Al, Cd, Cu, Fe, Pb, and Zn were additionally separated into operationally defined cytosolic (used as an indicator of exposure to bioavailable metal) and particulate fractions. Total concentrations of Cd, Cu, Hg, Pb, and Zn in sediments were consistent with documented upstream sources of acid mine drainage. Metal distribution patterns in H. californica and sediments were generally consistent for Cd, Cu, and Pb but inconsistent for Hg and Zn. Concentrations in H. californica indicated that bioavailable Cd, Cu, Pb, and Zn was transported at least 120 km downstream of the mine sources. Zinc in H. californica was elevated, but unlike sediments, did not decrease downstream. Mercury in H. californica was not elevated.

California↗
USGS2000

Stable isotope systematics of sulfate minerals

Stable isotope studies of sulfate minerals are especially useful for unraveling the geochemical history of geological systems. All sulfate minerals can yield sulfur and oxygen isotope data. Hydrous sulfate minerals, such as gypsum, also yield oxygen and hydrogen isotope data for the water of hydration, and more complex sulfate minerals, such as alunite and jarosite also yield oxygen and hydrogen isotope data from hydroxyl sites. Applications of stable isotope data can be divided into two broad categories: geothermometry and tracer studies. The equilibrium partitioning of stable isotopes between two substances, such as the isotopes of sulfur between barite and pyrite, is a function of temperature. Studies can also use stable isotopes as a tracer to fingerprint various sources of hydrogen, oxygen, and sulfur, and to identify physical and chemical processes such as evaporation of water, mixing of waters, and reduction of sulfate to sulfide. Studies of sulfate minerals range from low-temperature surficial processes associated with the evaporation of seawater to form evaporite deposits to high-temperature magmatic-hydrothermal processes associated with the formation of base-and precious-metal deposits. Studies have been conducted on scales from submicroscopic chemical processes associated with the weathering of pyrite to global processes affecting the sulfur budget of the oceans. Sulfate isotope studies provide important information to investigations of energy and mineral resources, environmental geochemistry, paleoclimates, oceanography (past and present), sedimentary, igneous, and metamorphic processes, Earth systems, geomicrobiology, and hydrology. One of the most important aspects of understanding and interpreting the stable isotope characteristics of sulfate minerals is the complex interplay between equilibrium and kinetic chemical and isotopic processes. With few exceptions, sulfate minerals are precipitated from water or have extensively interacted with water at some time in their history. Because of this nearly ubiquitous association with water, the kinetics of isotopic exchange reactions among dissolved species and solids are fundamental in dictating the isotopic composition of sulfate minerals. In general, the heavier isotope of sulfur is enriched in the higher oxidation state, such that under equilibrium conditions, sulfate minerals (e.g. barite, anhydrite) are expected to be enriched in the heavy isotope relative to disulfide minerals (e.g. pyrite, marcasite), which in turn are expected to be enriched relative to monosulfide minerals (e.g. pyrrhotite, sphalerite, galena) ( Sakai 1968 , Bachinski 1969 ). The kinetics of isotopic exchange among minerals with sulfur at the same oxidation state, such as sphalerite, and galena, are such that equilibrium is commonly observed. In contrast, isotopic equilibrium for exchange reactions between minerals of different oxidation states depends on factors such as the pH, time and temperature of reaction, the direction of reaction, fluid composition, and the presence or absence of catalysts ( Ohmoto and Lasaga 1982 ). The kinetics of oxygen isotope exchange between dissolved sulfate and water are extremely sluggish. Extrapolation of the high-temperature (100 to 300°C) isotopic exchange kinetic data of Chiba and Sakai (1985) to ambient temperatures suggests that it would take several billions of years for dissolved sulfate and seawater to reach oxygen isotopic equilibrium. In contrast, the residence time of sulfate in the oceans is only 7.9 million years ( Holland 1978 ). However, at higher temperatures (>200°C), oxygen isotopic exchange is sufficiently rapid to permit application of sulfate isotope geothermometry to geothermal systems and hydrothermal mineral deposits. In general, equilibrium prevails at low pH and high temperatures, whereas kinetic factors preclude equilibrium at low temperatures even at low pH. Thus, the sluggish kinetics of sulfur and oxygen isotope exchange reaction at low temperatures impair the use of these isotopes to understand the conditions of formation of sulfate minerals in these environments. However, because of these slow kinetics, the oxygen and sulfur isotopic compositions of sulfate minerals may preserve a record of the sources and processes that initially produced the dissolved sulfate, because the isotope ratios may not re-equilibrate during fluid transport and mineral precipitation. The first part of this chapter is designed to provide the reader with a basic understanding of the principles that form the foundations of stable isotope geochemistry. Next, an overview of analytical methods used to determine the stable isotope composition of sulfate minerals is presented. This overview is followed by a discussion of geochemical processes that determine the stable isotope characteristics of sulfate minerals and related compounds. The chapter then concludes with an examination of the stable isotope systematics of sulfate minerals in a variety of geochemical environments.

Reviews in Mineralogy and Geochemistry↗
USGS2000

Metal-sulfate salts from sulfide mineral oxidation

The observation of “efflorescences,” or the flowering of salts, associated with periods of dryness in soils, in closed-basin lakes, in rock outcrops, and in mines and mine wastes has been noted since early antiquity. The formation of metal-sulfate salts, in connection with the mining of metals, was a phenomenon well known to the early Greek and Roman civilizations. Alum, most commonly potash alum KAl(SO 4 ) 2 · 12H 2 O, which is from the Latin alumen , was extensively mined and used by goldsmiths, dyers, paper manufacturers, and physicians in ancient civilizations. It forms from the oxidation of pyrite in shales and slates and from oxidation of sulfurous gases in geothermal areas. The Greeks and the Romans described stalactites of atramentum (soluble metal-sulfate salts) that formed within mines and along rock faces (Agricola 1546, 1556). Furthermore, the toxic effects of these salts on animals were also noted. For example, in De Natura Fossilium , Agricola (1546) stated “….I mention the congealed acid juice which usually produces cadmia . It is white, hard, and so acrid that it can eat away walls, grills and even destroy all living matter.” Cadmia is thought to be derived from the oxidation of zinc, cobalt, and arsenic sulfides, such as cobaltite. He goes on to say that “Pyrite, unless it contains sulphates, is either a golden or silver color, rarely any other, while cadmia is black, yellow brown, or gray. The former will cure gatherings while the latter is a deadly poison and will destroy any living substance. It is used to kill grasshoppers, mice and flies.” These descriptions suggest the presence of arsenic compounds. The range of colors from white to black commonly is caused by different amounts of admixed pyrite with sulfate minerals. From the days of the Greek philosopher Theophrastus ( ca 325 BCE) and the Greek physician Dioscorides (first century CE), the efflorescent salts atramentum sutorium virida or melanterite (also called melanteria ) and atramentum sutorium caeruleum or chalcanthite were well known to form from the corrosion of pyrite and chalcopyrite by moisture (Agricola 1546, footnotes on p. 47–51). By the time of Pliny the Second (Caius Plinius Secundus, 23–79 CE), the names “green vitriol” for melanterite and “blue vitriol” for chalcanthite were in common use and continued to be used from the Middle Ages to the 20th century.

Reviews in Mineralogy and Geochemistry↗
USGS2000

Alunite-jarosite crystallography, thermodynamics, and geochronology

The alunite supergroup consists of more than 40 mineral species that have in common the general formula DG 3 ( T O 4 ) 2 (OH,H 2 O) 6 . The D sites are occupied by monovalent (e.g. K, Na, NH 4 , Ag, Tl, H 3 O), divalent (e.g. Ca, Sr, Ba, Pb), trivalent (e.g. Bi, REE) or more rarely quadrivalent (Th) ions; G is Al or Fe 3+ or rarely Ga or V; T is S 6+ , As 5+ , or P 5+ , and may include subordinate amounts of Cr 6+ or Si 4+ . Many of the minerals in this supergroup are exotic, having been described from relatively few localities worldwide, generally in association with ore deposits. Rarely are end-member compositions attained in these natural occurrences, and extensive solid solution is typical for one or more of the D , G , and T sites. In this chapter, the two solid-solution series considered in detail are alunite-natroalunite [KAl 3 (SO 4 ) 2 (OH) 6 – NaAl 3 (SO 4 ) 2 (OH) 6 ] and jarosite-natrojarosite [KFe 3 (SO 4 ) 2 (OH) 6 – NaFe 3 (SO 4 ) 2 (OH) 6 ]. These minerals are by far the most abundant naturally occurring species of the alunite supergroup. Minerals with the generalized formula cited above can be variously grouped, but the simplest initial subdivision is on the basis of Fe > Al versus Al > Fe. Further subdivision is generally made on the basis of the predominant cation within the two T O 4 sites. Thus, within the supergroup, the alunite group consists of minerals in which both of the T sites are occupied by sulfur. This leads to a total negative charge of four on the T O 4 sites. In the ideal formulas of some members of the supergroup [e.g. woodhouseite, CaAl 3 (PO 4 )(SO 4 )(OH) 6 ], half of the T sites are occupied by sulfur, and the other half by arsenic or phosphorus, which produces a total negative charge of five on the T O 4 sites. In still other end-members of the supergroup [e.g. crandallite, CaAl 3 (PO 4 ) 2 (OH) 5 (H 2 O), and arsenocrandallite, CaAl 3 (AsO 4 ) 2 (OH) 5 (H 2 O)], both of the T sites are occupied solely by phosphorus or arsenic, thus producing a total negative charge of six on the T O 4 sites (see Table 1 1 of Dutrizac and Jambor, this volume). In this chapter, however, the primary concern is with those minerals for which T O 4 is represented by SO 4 2− (Table 1 1 ). Precipitates with compositions near those of the end-members in the system alunite-natroalunite and jarosite-natrojarosite are readily prepared using sulfate salts. The products, however, almost invariably have a slight to appreciable deficiency in G 3+ , and have an apparent non-stoichiometry for D . The latter may reflect incorporation a H 3 O + , a solid solution that is difficult to prove because H 3 O + cannot be determined directly by wet-chemistry or microprobe methods. Nevertheless, the existence of two minerals in the alunite supergroup is dependent solely on their D -site predominance of H 3 O + , namely, hydronium jarosite [(H 3 O)Fe 3 (SO 4 ) 2 (OH) 6 ] and schlossmacherite [(H 3 O,Ca)Al 3 (SO 4 ) 2 (OH,H 2 O) 6 ]. This chapter is organized into four sections. In the first section, crystallographic data for alunite-natroalunite and jarosite-natrojarosite are presented and discussed. The second section describes available thermodynamic data for these two solid-solution series, in terms of properties of the end-members and mixing properties for intermediate compositions. The third section discusses the geochemistry and occurrences of alunite and jarosite, and the last section summarizes the published literature on the use of alunite and jarosite in geochronology.

Reviews in Mineralogy and Geochemistry↗
USGS2000

Water quality in the Sacramento River basin, California, 1994-98

This report summarizes major findings about water quality in the Sacramento River basin that emerged from an assessment conducted between 1994 and 1998 by the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Water quality is discussed in terms of local and regional issues and compared to conditions found in all 36 NAWQA study areas assessed to date. Findings are also explained in the context of selected national benchmarks, such as those for drinking-water quality and the protection of aquatic organisms.

Circular↗
USGS2000

Mercury contamination from historic gold mining in California

Mercury contamination from historic gold mines represents a potential risk to human health and the environment. This fact sheet provides background information on the use of mercury in historic gold mining and processing operations in California, and describes a new USGS project that addresses the potential risks associated with mercury from these sources, with emphasis on historic hydraulic mining areas. Miners used mercury (quicksilver) to recover gold throughout the western United States at both placer (alluvial) and hardrock (lode) mines. The vast majority of mercury lost to the environment in California was from placer-goldmines, which used hydraulic, drift, and dredging methods. At hydraulic mines, placer ores were broken down with monitors (or water cannons, fig. 1) and the resulting slurry was directed throughsluices and drainage tunnels, where goldparticles combined with liquid mercury to form gold?mercury amalgam. Loss ofmercury in this process was 10 to 30 percent per season (Bowie, 1905), resulting in highly contaminated sediments at mine sites (fig. 2). Elevated mercury concentrations in present-day mine waters and sediments indicate thathundreds to thousands of pounds of mercury remain at each of the many sites affected by hydraulic mining. High mercury levels in fish, amphibians, and invertebrates downstream of the hydraulic mines are a consequence of historic mercury use. On the basis of USGS studies and other recent work, a better understanding is emerging of mercury distribution, ongoing transport, transformation processes, and the extent of biological uptake in areas affected by historic gold mining. This information will be useful to agencies responsible for prudent land and resource management and for protecting public health.

California↗
USGS2000

Mercury bioaccumulation in fish in a region affected by historic gold mining: The South Yuba River, Deer Creek, and Bear River watersheds, California, 1999

Mercury that was used historically for gold recovery in mining areas of the Sierra Nevada continues to enter local and downstream water bodies, including the Sacramento Delta and the San Francisco Bay of northern California. Methylmercury is of particular concern because it is the most prevalent form of mercury in fish and is a potent neurotoxin that bioaccumulates at successive trophic levels within food webs. In April 1999, the U.S. Geological Survey, in cooperation with several other agencies the Forest Service (U.S. Department of Agriculture), the Bureau of Land Management, the U.S. Environmental Protection Agency, the California State Water Resources Control Board, and the Nevada County Resource Conservation District began a pilot investigation to characterize the occurrence and distribution of mercury in water, sediment, and biota in the South Yuba River, Deer Creek, and Bear River watersheds of California. Biological samples consisted of semi-aquatic and aquatic insects, amphibians, bird eggs, and fish. Fish were collected from 5 reservoirs and 14 stream sites during August through October 1999 to assess the distribution of mercury in these watersheds. Fish that were collected from reservoirs included top trophic level predators (black basses, Micropterus spp.) intermediate trophic level predators [sunfish (blue gill, Lepomis macrochirus; green sunfish, Lepomis cyanellus; and black crappie, Poxomis nigromaculatus)] and benthic omnivores (channel catfish, Ictularus punctatus). At stream sites, the species collected were upper trophic level salmonids (brown trout, Salmo trutta) and upper-to-intermediate trophic level salmonids (rainbow trout, Oncorhynchus mykiss). Boneless and skinless fillet portions from 161 fish were analyzed for total mercury; 131 samples were individual fish, and the remaining 30 fish were combined into 10 composite samples of three fish each of the same species and size class. Mercury concentrations in samples of black basses (Micropterus spp.), including largemouth, smallmouth, and spotted bass, ranged from 0.20 to 1.5 parts per million (ppm), wet basis. Mercury concentrations in sunfish ranged from less than 0.10 to 0.41 ppm (wet). Channel catfish had mercury concentrations from 0.16 to 0.75 ppm (wet). The range of mercury concentrations observed in rainbow trout was from 0.06 to 0.38 ppm (wet), and in brown trout was from 0.02 to 0.43 ppm (wet). Mercury concentrations in trout were greater than 0.3 ppm in samples from three of 14 stream sites. Mercury at elevated concentrations may pose a health risk to piscivorous wildlife and to humans who eat fish on a regular basis. Data presented in this report may be useful to local, state, and federal agencies responsible for assessing the potential risks associated with elevated levels of mercury in fish in the South Yuba River, Deer Creek, and Bear River watersheds.

California↗
USGS2000

Metals transport in the Sacramento River, California, 1996-1997; volume 1: Methods and data

Metals transport in the Sacramento River, northern California, was evaluated on the basis of samples of water, suspended colloids, streambed sediment, and caddisfly larvae that were collected on one to six occasions at 19 sites in the Sacramento River Basin from July 1996 to June 1997. Four of the sampling periods (July, September, and November 1996; and May-June 1997) took place during relatively low-flow conditions and two sampling periods (December 1996 and January 1997) took place during high-flow and flooding conditions; respectively. Tangential-flow ultrafiltration with 10,000 nominal molecular weight limit, or daltons (0.005 micrometer equivalent), pore-size membranes was used to separate metals in streamwater into ultrafiltrate (operationally defined dissolved fraction) and retentate (colloidal fraction) components, respectively. Conventional filtration with capsule filters (0.45 micrometer pore-size) and membrane filters (0.40 micrometer pore-size) and total-recoverable analysis of unfiltered (whole-body) samples were done for comparison at all sites. Because the total-recoverable analysis involves an incomplete digestion of particulate matter, a more reliable measurement of whole-water concentrations is derived from the sum of the dissolved component that is based on the ultrafiltrate plus the suspended component that is based on a total digestion of colloid concentrates from the ultra-filtration retentate. Metals in caddisfly larvae were determined for whole-body samples and cytosol extracts, which are intercellular solutions that provide a more sensitive indication of the metals that have been bioaccumulated. Trace metals in acidic, metal-rich drainage from abandoned and inactive sulfide mines were observed to enter the Sacramento River system (specifically, into both Shasta Lake and Keswick Reservoir) in predominantly dissolved form, as operationally defined using ultrafiltrates. The predominant source of acid mine drainage to Keswick Reservoir is Spring Creek, which drains the Iron Mountain mine area. Copper concentrations in filtered samples from Spring Creek taken during December 1996, January 1997, and May 1997 ranged from 420 to 560 micrograms per liter. Below Keswick Dam, copper concentrations in conventionally filtered samples ranged from 0.5 micrograms per liter during September 1996 to 9.4 micrograms per liter during January 1997; the latter concentration exceeded the applicable water-quality standard. The proportion of trace metals that was dissolved (versus colloidal) in samples collected at Shasta and Keswick dams decreased in the order cadmium zinc > copper > aluminum iron lead mercury. At four sampling sites on the Sacramento River at various distances downstream of Keswick Dam (Bend Bridge, 71 kilometers; Colusa, 256 kilometers; Verona, 360 kilometers; and Freeport, 412 kilometers) concentrations of these seven metals were predominantly colloidal during both high- and low-flow conditions. Because copper compounds are used extensively as algaecides in rice farming, agricultural drainage at the Colusa Basin Drain was sampled in June 1997 during a period shortly after copper applications to newly planted rice fields. Copper concentrations ranged from 1.3 to 3.0 micrograms per liter in filtered samples and from 12 to 13 micrograms per liter in whole-water samples (total recoverable analysis). These results are consistent with earlier work by the U.S. Geological Survey indicating that copper in rice-field drainage likely represents a detectable, but relatively minor source of copper to the Sacramento River. Lead isotope data from suspended colloids and streambed sediments collected during October and November 1996 indicate that lead from acid mine drainage sources became a relatively minor component of the total lead at the site located 71 kilometers downstream of Keswick Dam and beyond. Cadmium, copper, and zinc concentrations in caddisfly larvae were elevated at several sites downstream of Keswick Dam, but concentrations of aluminum, iron, lead, and mercury were relatively low, especially in the cytosol extracts. Cadmium showed the highest degree of bioaccumulation in whole-body and cytosol analyses, relative to an unmineralized control site (Cottonwood Creek). Cadmium bioaccumulation persisted in samples collected as far as 118 kilometers downstream of Keswick Dam, consistent with transport in a form more bioavailable than lead.

California↗
USGS1999

Negative pH and extremely acidic mine waters from Iron Mountain, California

Extremely acidic mine waters with pH values as low as -3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as -4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

Environmental Science & Technology↗
USGS1999

Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the iron mountain superfund site, California

The Richmond Mine of the Iron Mountain copper deposit contains some of the most acid mine waters ever reported. Values of pH have been measured as low as -3.6, combined metal concentrations as high as 200 g/liter, and sulfate concentrations as high as 760 g/liter. Copious quantities of soluble metal sulfate salts such as melanterite, chalcanthite, coquimbite, rhomboclase, voltaite, copiapite, and halotrichite have been identified, and some of these are forming from negative-pH mine waters. Geochemical calculations show that, under a mine-plugging remediation scenario, these salts would dissolve and the resultant 600,000-m3 mine pool would have a pH of 1 or less and contain several grams of dissolved metals per liter, much like the current portal effluent water. In the absence of plugging or other at-source control, current weathering rates indicate that the portal effluent will continue for approximately 3,000 years. Other remedial actions have greatly reduced metal loads into downstream drainages and the Sacramento River, primarily by capturing the major acidic discharges and routing them to a lime neutralization plant. Incorporation of geochemical modeling and mineralogical expertise into the decision-making process for remediation can save time, save money, and reduce the likelihood of deleterious consequences.

Proceedings of the National Academy of Sciences of↗
USGS1997

Geochemical modeling of water-rock interactions in mining environments

Geochemical modeling is a powerful tool for evaluating geochemical processes in mining environments. Properly constrained and judiciously applied, modeling can provide valuable insights into processes controlling the release, transport, and fate of contaminants in mine drainage. This chapter contains 1) an overview of geochemical modeling, 2) discussion of the types of models and computer programs used, 3) description of a procedure for screening water analyses for modeling input, and 4) examples of the application of modeling for interpreting geochemical processes in mining environments. Three general strategies in current use to interpret water-rock interactions are statistical analysis, “inverse” modeling, and “forward” modeling. Multivariate correlation analysis, factor analysis, cluster analysis, and other statistical techniques can group water-chemistry data into sets that may relate to hydrogeochemical processes (Drever, 1988; Puckett and Bricker, 1992). In the field of geochemical exploration, statistical analysis is used widely to treat large data sets of rock and sediment chemistry (e.g., Garrett, 1989). No physical or chemical principles are involved directly in these statistical treatments, hence they are not considered further in this chapter. Nevertheless, statistical analysis can be a useful tool in organizing complex geochemical data for interpretation.

Book chapter↗
USGS1995

Hydrogeology and geochemistry of acid mine drainage in ground water in the vicinity of Penn Mine and Camanche Reservoir, Calaveras County, California: First-year summary

Acid drainage from the Penn Mine in Calaveras County, California, has caused contamination of ground water between Mine Run Dam and Camanche Reservoir. The Penn Mine was first developed in the 1860's primarily for copper and later produced lesser amounts of zinc, lead, silver, and gold from steeply dipping massive sulfide lenses in metamorphic rocks. Surface disposal of sulfidic waste rock and tailings from mine operations has produced acidic drainage with pH values between 2.3 and 2.7 and elevated concentrations of sulfate and metals, including copper, zinc, cadmium, iron, and aluminum. During the mine's operation and after its subsequent abandonment in the late 1950's, acid mine drainage flowed down Mine Run into the Mokelumne River. Construction of Camanche Dam in 1963 flooded part of the Mokelumne River adjacent to Penn Mine. Surface-water diversions and unlined impoundments were constructed at Penn Mine in 1979 to reduce runoff from the mine, collect contaminated surface water, and enhance evaporation. Some of the contaminated surface water infiltrates the ground water and flows toward Camanche Reservoir. Ground- water flow in the study area is controlled by the local hydraulic gradient and the hydraulic characteristics of two principal rock types, a Jurassic metavolcanic unit and the underlying Salt Spring slate. The hydraulic gradient is west from Mine Run impoundment toward Camanche Reservoir. The median hydraulic conductivity was about 10 to 50 times higher in the metavolcanic rock (0.1 foot per day) than in the slate (0.002 to 0.01 foot per day); most flow occurs in the metavolcanic rock where hydraulic conductivity is as high as 50 feet per day in two locations. The contact between the two rock units is a fault plane that strikes N20?W, dips 20?NE, and is a likely conduit for ground-water flow, based on down-hole measurements with a heatpulse flowmeter. Analyses of water samples collected during April 1992 provide a comprehensive characterization of ground water below Mine Run Dam at the Penn Mine. Specific conductance of the samples ranged from 1,810 to 18,000 microsiemens per centimeter. pH values of sampled ground water ranged from 3.7 to 7.8. Dissolved constituents in ground water ranged from less than 0.010 to 86 milligrams per liter for copper, from less than 0.010 to 240 milligrams per liter for iron, from less than 0.01 to 250 milligrams per liter for aluminum, and from 0.020 to 600 milligrams per liter for zinc. A contaminated ground-water plume appears to originate in the metavolcanic unit along the north abutment of Mine Run Dam. The plume is characterized by low pH, high concentrations of sulfate and dissolved metals, and enrichment of the heavy stable isotopes of hydrogen and oxygen. Dissolved iron and sulfate correlate positively, suggesting pyrite as the probable source of these elements. The concentrations of some dissolved constituents apparently are controlled by equilibrium with solid mineral phases. Poorly crystalline hydrous ferric oxide and microcrystalline gibbsite are close to saturation in ground water with pH values between 4 and 7.8 and probably control the solubility of Fe 3+ and Al 3+ , respectively. Using a range of bulk hydraulic conductivity values for the metavolcanic unit from the median value (0.1 foot per day) to the highest values (50 feet per day), together with a representative cross-sectional area (3,000 square feet) for the contaminated ground-water plume and a hydraulic gradient of 0.14 from August 1992, the following range in ground-water flow rates is estimated by Darcy's law: 42 to 21,000 cubic feet per day, or 10 5 to 5x10 7 gallons per year. Multiplying this estimated range in ground-water flow by representative metal concentrations from the contaminated plume gives the following estimates for annual metal transport to Camanche Reservoir by ground water: 86 to 42,000 pounds of copper; 310 to 150,000 pounds of zinc; and 1.5 to 750 pounds of cadmium.

California↗