Walter H. Ficklin

Separation of arsenic(III) and arsenic(V) in ground waters by ion-exchange.

The predominant species of arsenic in ground water are probably arsenite and arsenate. These can be separated with a strong anion-exchange resin (Dowex 1 x 8; 100-200 mesh, acetate form) in a 10 cm x 7 mm column. Samples are filtered and acidified with concentrated hydrochloric acid (1 ml per 100 ml of sample) at the sample site. Five ml of the acidified sample are used for the separation. At this acidity, As(III) passes through the acetate-form resin, and As(V) is retained. As(V) is eluted by passage of 0.12M hydrochloric acid through the column (resulting in conversion of the resin back into the chloride form). Samples are collected in 5-ml portions up to a total of 20 ml. The arsenic concentration in each portion is determined by graphite-furnace atomic-absorption spectrophotometry. The first two fractions give the As(III) concentration and the last two the As(V) concentration. The detection limit for the concentration of each species is 1 mug l .

Anomalous gold, antimony, arsenic, and tungsten in ground water and alluvium around disseminated gold deposits along the Getchell Trend, Humboldt County, Nevada

Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden. Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured Eh and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured Eh and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (μg/L); Sb, from less than 0.1 to 250 μg/L; and W, from 1 to 260 μg/L. In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits.

Extraction and speciation of arsenic in lacustrine sediments

Arsenic was partially extracted with 4.OM hydrochloric acid, from samples collected at 25-cm intervals in a 350-cm column of sediment at Milltown Reservoir, Montana and from a 60-cm core of sediment collected at the Cheyenne River Embayment of Lake Oahe, South Dakota. The sediment in both reservoirs is highly contaminated with arsenic. The extracted arsenic was separated into As(III) and As(V) on acetate form Dowex 1-X8 ion-exchange resin with 0.12M HCl eluent. Residual arsenic was sequentially extracted with KClO(3) and HCl. Arsenic was determined by graphite-furnace atomic-absorption spectrometry. The analytical results define oxidized and reduced zones in the sediment columns.

Hydrogeochemical prospecting for porphyry copper deposits in the tropical-marine climate of Puerto Rico

Abstract A hydrogeochemical survey utilizing waters from streams and springs was conducted in the area of two known porphyry copper deposits in the tropical-marine climate of westcentral Puerto Rico. The most important pathfinder for regional hydrogeochemical surveys is sulfate which reflects the associated pyrite mineralization. Because of increased mobility due to intense chemical weathering and the low pH environment, dissolved copper can also be used as a pathfinder for regional surveys and has the advantage of distinguishing barren pyrite from pyrite associated with copper mineralization. For follow-up surveys, the most important pathfinders are copper, sulfate, pH, zinc, and fluoride. High concentrations of dissolved copper and moderate concentrations of sulfate is a diagnostic indication of nearby sources of copper minerals. An understanding of the geochemical processes taking place in the streambeds and the weathering environment, such as the precipitation of secondary copper minerals, contributes to the interpretation of the geochemical data and the selection of the most favorable areas for further exploration.

The Separation of Tungstate and Molybdate by Ion Chromatography and its Application to Natural Waters

Abstract Ion chromatographic separation of tungstate and molybdate is achieved using a 3 × 250 mm standard anion separator column, a 0.006 M sodium carbonate eluent, a standard anion suppressor column, and a flow rate of 90 ml/hr. Elution of peaks for the species tungstate and molybdate occurs at 9 and 12 minutes, respectively, and peak heights are distinguishable from the base line at concentrations of 0.1 mg/L, using a full scale deflection of 10 μmho and a dual-pen recorder. Tungstate and molybdate must be concentrated from 1 L of water by collecting them on a chelating resin after the pH of the water is adjusted to between 1 and 2. Tungstate and molybdate are eluted with concentrated ammonium hydroxide. The amnonia is evaporated, leaving a water solution containing tungstate and molybdate. About 90% of the tungsten and molybdenum is recovered, with a relative standard deviation of about 15% at the 5 μg/L level. Natural concentrations of tungsten or molybdenum as small as 1 μg/L are measured by this te...

Geochemical exploration for copper-nickel deposits in the cool-humid climate of northeastern Minnesota

Abstract Water was used as a medium for geochemical exploration to detect copper-nickel mineralization along the basal zone of the Duluth Complex. Ni2+ is the most important pathfinder for the detection of the mineralized rocks, followed by Cu2+ and SO42− and to a lesser extent Mg2+ and SiO2. A normalized sum plot using these species defines the mineralization more consistently than a single-element plot, mainly because the absence of one variable does not significantly influence the normalized sum value. A hydrogeochemical survey was conducted in an area of known copper-nickel mineralization in the cool-humid climate of northeastern Minnesota. The area is covered with glacial drift, and wetlands are abundant. Modeling of the chemistry of waters indicates that the waters are oxidizing and have a pH of 7 or less. The most important pathfinder species in the waters, Cu2+, Ni2+, and SO42−, are derived from the simple weathering of sulfide minerals and are mobile in the waters in this environment. Plots of Cu and Ni concentrations in soils show that Cu followed by Ni are the most useful indicator elements for delineating copper-nickel mineralization. The ability of soils and water to delineate the mineralization supports the use of both media for geochemical exploration in this cool-humid environment. In the wetlands, abundant water is available and soils are scarce or absent; where soils are abundant, waters are generally scarce or absent. The use of both media is recommended for geochemical exploration in this environment.

The chemical, physical and structural properties of estuarine ice in Great Bay, New Hampshire

Abstract The purpose of this study was to provide general information on the chemical, physical and structural properties of estuarine ice and show how it compares with sea ice found at higher latitudes in order to determine whether the ice in Great Bay can be used as an analog in the study of arctic sea ice. Ice cores and water samples were collected during the 1983–1984 winter season at Adams Point in Great Bay, New Hampshire. Concentrations of chloride, nitrogen (as nitrate and nitrite), bromide, phosphate, sulfate and silicate were determined for samples chosen on the basis of identifiable stratigraphic layers (i.e. bubble size and shape, sediment layers, etc.). Similarities between ice formation in Great Bay and those in the arctic regions include the nature of the freezing process and the ice types produced. In addition, the distribution and concentration of chemical constituents were found to be similar to those observed in arctic sea ice. Factors affecting the chemistry of the ice in Great Bay include rainfall during the freezing season, the presence of sediment layers in the ice cores, the nature of incorporation of brine into the crystal structure of the ice and the drainage of brine.