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Surface water chemistry and hydrology of two subalpine watersheds in Rocky Mountain National Park, Colorado
No abstract available.
Authigenic barite in varved clays: result of marine transgression over freshwater deposits and associated changes in interstitial water chemistry
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The source of Witwatersrand gold: Evidence from uraninite chemistry
An in-situ LA-ICP-MS study of different generations of uraninite from the Mesoarchaean Witwatersrand gold palaeoplacer deposits revealed unusually high Au concentrations in rounded, detrital uraninite grains but no detectable Au in secondary, hydrothermally mobilised uraninite. A Au-enriched uraninite-bearing magmatic host is suggested as a significant source for detrital gold in the Witwatersrand sediments.
Complex interactions between global change drivers influence mountain forest and slpine GHG sequestration and stream chemistry
Many mountain ecosystems are experiencing coincident increases in temperature, levels of atmospheric carbon dioxide (CO2) and atmospheric nitrogen (N) deposition. All are important controls on rates of plant growth, soil microbial activity, nutrient cycling, and stream N export. It is difficult for experimental studies to explore ecosystem responses to more than one or two treatments at plot, let alone catchment, scale. One might expect, however, ecosystems to respond differently to the combined global change drivers than to climate, CO2, or N alone. We explored this question for nine mountain catchments over the period 1980- 2075 with a simulation model.
The chemistry of five accessory rock-forming apatites
Chemical and physical data are given for five samples of rock-forming apatite from diverse geologic environments in Nevada and Colorado. Four of these apatites contain rare-earth assemblages in which the cerium group is well represented but the yttrium group predominates. The fifth apatite contains a highly fractionated assemblage of the lighter (cerium group) rare earths similar to the assemblage typical of alkulic rocks.
Bottom-sediment chemistry in Devil's Lake, northeast North Dakota
Devils Lake is a 200 km 2 terminal lake that contains sodium sulfate type water. Dissolved solids concentrations range from about 3,500 mg/L to 10,000 mg/L depending on location To investigate geochemical processes in the bottom sediments of Devils Lake, sediment cores were collected at two sites in the western half of the lake during a period of bottom water oxygen depletion. The upper 10 cm of the sediments consist of about 60 weight percent silicates (quartz, feldspar, and clays) 35 weight percent carbonates and 5 weight percent organic material. At depths between 1 and 3 cm in the sediments bacterial sulfate reduction and associated degradation of organic material cause minima in sulfate concentrations and δ 13 C values of dissolved inorganic carbon and maxima in alkalinity, ammonia, phosphate, and sulfide concentrations and δ 34 S values of dissolved sulfate. Downward increases of sodium, magnesium, potassium, and calcium concentrations result from upward diffusion of ions from saline pore water and dissolving sulfate minerals below 30 cm depth in the sediments. High magnesium calcite 8 mole percent MgCO 3 is the most abundant carbonate at the sediment surface. With increasing depth abundances of high magnesium carbonate decrease and abundances of low magnesium calcite aragonite and dolomite increase. Carbon isotope compositions of bulk carbonates range from δ 13 C = -0.7 to +0.5%. These values are close to equilibrium with dissolved inorganic carbon in lake water ( δ 13 C = -2%) but far from equilibrium with dissolved inorganic carbon in pore water ( δ 13 C = -16.3- -10/0%). Disequilibrium between pore water and carbonates suggests that the carbonates did not recrystallize substantially in the presence of pore water. Therefore the change of carbonate mineral proportions with depth in the sediments is due mainly to temporal changes in the proportions of endogenic, detrital, and biologic carbonates that were deposited on the lake bottom rather than postdepositional carbonate diagenesis.
Role of blanket deposits on the hydrology and water chemistry of the limestone water-table aquifer within the north coast of Puerto Rico through interpretation of geochemical data
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Pilot study for the characterization of sediment chemistry, sediment toxicity, and benthic invertebrate community structure for PCB-contaminated sediments from the Upper Hudson River, New York
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Using spring-water chemistry to assess groundwater contamination and ages of shallow and deep ground water flow systems
No abstract available.
Effects of selective handling of pyritic, acid-forming materials on the chemistry of pore gas and ground water at a reclaimed surface coal mine in Clarion County, PA, USA
A change from dragline to “selective handling” mining methods at a reclaimed surface coal mine in western Pennsylvania did not significantly affect concentrations of metals in ground water because oxidation of pyrite and dissolution of siderite were not abated. Throughout the mine, placement of pyritic material near the land surface facilitated the oxidation of pyrite, causing the consumption of oxygen (O 2 ) and release of acid, iron, and sulfate ions. Locally in the unsaturated zone, water sampled within or near pyritic zones was acidic, with concentrations of sulfate exceeding 3,000 milligrams per liter (mg/L). However, acidic conditions generally did not persist below the water table because of neutralization by carbonate minerals. Dissolution of calcite, dolomite, and siderite in unsaturated and saturated zones produced elevated concentrations of carbon dioxide (CO 2 ), alkalinity, calcium, magnesium, iron, and manganese. Alkalinity concentrations of 600 to 800 mg/L as CaCO 3 were common in water samples from the unsaturated zone in spoil, and alkalinities of 100 to 400 mg/L as CaCO 3 were common in ground-water samples from the underlying saturated zone in spoil and bedrock. Saturation indices indicated that siderite could dissolve in water throughout the spoil, but that calcite dissolution or precipitation could occur locally. Calcite dissolution could be promoted as a result of pyrite oxidation, gypsum precipitation, and calcium ion exchange for sodium. Calcite precipitation could be promoted by evapotranspiration and siderite dissolution, and corresponding increases in concentrations of alkalinity and other solutes. Partial pressures of O 2 (Po 2 ) and CO 2 (Pco 2 ) in spoil pore gas indicated that oxidation of pyrite and precipitation of ferric hydroxide, coupled with dissolution of calcite, dolomite, and siderite were the primary reactions affecting water quality. Highest vertical gradients in Po 2 , particularly in the near-surface zone (0-1 m), did not correlate with concentrations of total sulfur in spoil. This lack of correlation could indicate that total sulfur concentrations in spoil do not reflect the amount of reactive pyrite or that oxidation rates can be controlled more by rates of O 2 diffusion than the amount of pyrite. Hence, if placed in O 2 -rich zones near the land surface, even small amounts of disseminated pyritic material can be relatively significant sources of acid and mineralized water.
Acid base accounting--An improved method of interpreting overburden chemistry to predict the quality of coal-mine drainage
Acidic mine drainage (AMD), which results from the accelerated oxidation of pyrite (FeS 2 ) in mined coal and overburden, has contaminated thousands of miles of streams in the Appalachian region of the United States. Acid‐base accounting (ABA), which simplifies the complex hydrogeochemical system through use of a limited number of variables, commonly is used to predict the post‐mining occurrence of AMD. ABA involves the measurement of sulfur (S) and carbonate (CO 3 ) concentrations in coal‐bearing rocks and the computation of overburden net‐neutralization potential (NNP) in units of tons of calcium carbonate per thousand tons of rock (tons CaCO3/1,000 ton) (Sobek and others, 1978). ABA was developed on the assumption that the stoichiometry of the following overall reaction of FeS 2 and CaCO 3 can be used to convert acid (H + ) into units of CaCO 3 : FeS 2 + CaCO 3 + 3.75 O 2 + 1.5 H 2 O --> Fe(OH) 3 + 2 SO 4 -2 + 2 Ca +2 + 2 CO 2 (g), (1) where the H + from 1 mol (mole) of FeS2 [64 g (gram) of S] is neutralized by 2 mol of CaCO3 (200 g). This method presumes that gaseous carbon dioxide (CO2 ) will exsolve. Thus 3.125 g CaCO3 will neutralize the acid from 1 g S; or 31.25 tons of CaCO 3 will neutralize the acid from 1,000 tons of rock that contains 1.0 percent pyritic S. The total S concentration, in percent, is multiplied by 31.25 and is assumed to be pyritic and acid‐producing in order to compute maximum potential acidity (MPA) for comparison with neutralization potential (NP), in units of tons CaCO 3 /1,000 ton (Sobek and others, 1978). NNP is computed by subtracting mass‐ weighted MPA from NP (Smith and Brady, 1990). if the value of NNP is less than zero, the acid‐producing potential of the rock exceeds its neutralization potential and if mined, therefore, would be expected to produce AMD.
Secondary minerals and acid mine-water chemistry
No abstract available.
Ground water to surface water: Chemistry of thermal outflows in Yellowstone National Park
Geothermal waters in the earth’s subsurface boil with steam separation and may mix with dilute ground waters (that may or may not contain sulfuric acid from sulfur oxidation), resulting in a wide range of compositions when they discharge and emerge at the surface. As they discharge onto the ground surface they undergo evaporative cooling, degassing, oxidation, and mineral precipitation. Within this aquatic environment of rapidly changing physical and chemical parameters, numerous microbial communities develop—some of which affect oxidation and mineral precipitation. Microbes are responsible for rapid oxidation of iron and arsenic in thermal outflows, and for catalyzing the production of sulfuric acid from the oxidation of elemental sulfur. The attractive visual display of colors observed in Yellowstone’s geothermal waters reflects this interplay of physical, chemical, and biological phenomena. Oxidation of dissolved sulfide to thiosulfate occurs abiotically, and thiosulfate can be found in many of Yellowstone’s thermal waters—at any pH, temperature, and composition. Polythionates, on the other hand, are rarely found in Yellowstone waters but are associated with sulfur hydrolysis in Cinder Pool. Oxidation rates of iron and arsenic in overflows have been estimated at 1-3 mM/h and 0.04-0.1 mM/h, respectively—orders of magnitude faster than the abiotic rate. The abiotic production of thiosulfate from oxidation of dissolved sulfi de at Angel Terrace and Ojo Caliente is about 3-30 µM/min, faster by 2-3 orders of magnitude than the laboratory rate at 25°C. The partitioning of dissolved sulfide between that volatilized to the air and that oxidized to thiosulfate has been estimated at Angel Terrace and at Ojo Caliente. For the pH range of 6-8 and the temperature range of 50-93°C, 67-86% of the dissolved sulfide is lost to the atmosphere and 10-33% is oxidized to thiosulfate. Only a very small percentage, if any, forms elemental sulfur under these conditions.
Deep evaporitic strata off New York and New Jersey-Evidence from interstitial water chemistry of drill cores
No abstract available.