Stephen A. Wilson

Metal emissions from Kilauea, and a suggested revision of the estimated worldwide metal output by quiescent degassing of volcanoes

Abstract Measurements of a large suite of metals (Pb, Cd, Cu, Zn and several others) and sulfur at Kilauea volcano over an extended period of time has yielded a detailed record of the atmospheric injection of ordinarily-rare metals from this quiescently degassing volcano, representative of an important type. We have combined the Kilauea data with data of recent studies by others (emissions from volcanoes in the Indonesian arc; the large Laki eruption of two centuries ago; Etna; estimates of total volcanic emissions of sulfur) to form the basis for a new working estimate of the rate of worldwide injection of metals to the atmosphere by volcanoes. The new estimate is that volcanoes inject a substantially smaller mass of ordinarily-rare metals into the atmosphere than was stated in a widely cited previous estimate [J.O. Nriagu, A global assessment of natural sources of atmospheric trace metals, Nature 338 (1989) 47–49]. Our estimate, which is an upper limit, is an annual injection mass of about 10,000 tons of the metals considered, versus the earlier estimate of about 23,000 tons. Also, the proportions of the metals are substantially different in our new estimate.

Development of a standard reference material for Cr(VI) in contaminated soil

Over the last several decades, considerable contamination by hexavalent chromium has resulted from the land disposal of Chromite Ore Processing Residue (COPR). COPR contains a number of hexavalent chromium-bearing compounds that were produced in high temperature industrial processes. Concern over the carcinogenic potential of this chromium species, and its environmental mobility, has resulted in efforts to remediate these waste sites. To provide support to analytical measurements of hexavalent chromium, a candidate National Institute of Standards and Technology (NIST) Standard Reference Material® (SRM 2701), having a hexavalent chromium content of approximately 500 mg kg−1, has been developed using material collected from a waste site in Hudson County, New Jersey, USA. The collection, processing, preparation and preliminary physico–chemical characterization of the material are discussed. A two-phase multi-laboratory testing study was carried out to provide data on material homogeneity and to assess the stability of the material over the duration of the study. The study was designed to incorporate several United States Environmental Protection Agency (USEPA) determinative methods for hexavalent chromium, including Method 6800 which is based on speciated isotope dilution mass spectrometry (SIDMS), an approach which can account for chromium species inter-conversion during the extraction and measurement sequence.

Determination of chloride in geological samples by ion chromatography

Abstract Samples of silicate rocks are prepared by sodium carbonate fusion and then treated by ion chromatography. The method was tested for geological standards with chloride concentration between 0.003 and 3%. Observed chloride concentrations comparedd favorably with literature values. The relative standard deviation and detection limit for the method were 8% and 7 ppm, respectively. Up to 30 determination per 24-hour period were possible.

The Determination of Fluoride in Geologic Samples by Ion Chromatography

Abstract A method is described for the determination of fluoride in geologic materials utilizing a sodium carbonate fusion and an ion chromatographic method of analysis. Excellent agreement is observed with published values for geologic standards ranging from 0.01% to 6% fluoride in the sample. Estimates of precision were based upon the repetitive analysis of United States Geological Survey standard GSP-1. Results indicate a relative standard deviation for the method of 5%. Detection limits were estimated to be 8 ppm fluoride in the sample at the 90% confidence level.

The Determination of Sulfur and Chlorine in Coals and Oil Shales Using Ion Chromatography

Abstract The determination of sulfur and chlorine in coal and oil shale standards is reported. The procedure utilizes a sample decomposition using Eschkas mixture, followed by an ion chromatographic determination. The method was tested on samples with concentrations ranging from 0.004 to 0.35 percent chlorine and 0.05 to 4.4 percent sulfur. Results compare favorably with values reported in the literature. The detection limits for chlorine and sulfur were 10 and 13 ppm and the precision of the method expressed as a percent relative standard deviation was 6 percent and 5 percent for chlorine and sulfur respectively. Using this method a single operator can prepare and analyze as many as 30 samples per day.

Development of Standardized Lunar Regolith Simulant Materials

Lunar exploration requires scientific and engineering studies using standardized testing procedures that ultimately support flight certification of technologies and hardware. It is necessary to anticipate the range of source materials and environmental constraints that are expected on the Moon and Mars, and to evaluate in-situ resource utilization (ISRU) coupled with testing and development. We describe here the development of standardized lunar regolith simulant (SLRS) materials that are traceable inter-laboratory standards for testing and technology development. These SLRS materials must simulate the lunar regolith in terms of physical, chemical, and mineralogical properties. A summary of these issues is contained in the 2005 Workshop on Lunar Regolith Simulant Materials [l]. Lunar mare basalt simulants MLS-1 and JSC-1 were developed in the late 1980s. MLS-1 approximates an Apollo 11 high-Ti basalt, and was produced by milling of a holocrystalline, coarse-grained intrusive gabbro (Fig. 1). JSC-1 approximates an Apollo 14 basalt with a relatively low-Ti content, and was obtained from a glassy volcanic ash (Fig. 2). Supplies of MLS-1 and JSC-1 have been exhausted and these materials are no longer available. No highland anorthosite simulant was previously developed. Upcoming lunar polar missions thus require the identification, assessment, and development of both mare and highland simulants. A lunar regolith simulant is manufactured from terrestrial components for the purpose of simulating the physical and chemical properties of the lunar regolith. Significant challenges exist in the identification of appropriate terrestrial source materials. Lunar materials formed under comparatively reducing conditions in the absence of water, and were modified by meteorite impact events. Terrestrial materials formed under more oxidizing conditions with significantly greater access to water, and were modified by a wide range of weathering processes. The composition space of lunar materials can be modeled by mixing programs utilizing a low-Ti basalt, ilmenite, KREEP component, high-Ca anorthosite, and meteoritic components. This approach has been used for genetic studies of lunar samples via chemical and modal analysis. A reduced composition space may be appropriate for simulant development, but it is necessary to determine the controlling properties that affect the physical, chemical and mineralogical components of the simulant.

The physical preparation of geologic samples for chemical analysis using laboratory robotics

Abstract An automated system to grind geologic samples has been successfully tested. A Zymate II robotic system, along with specially designed or modified hardware, was used to process partially pulverized geologic samples. the system is capable of processing samples on a 24-hour basis with an average per-samples grinding time of 12.4 minutes. A sample grinding period is followed by a cleanout sequence of air purges, vacuuming and grinding for surface cleaning with quartz sand. Routine operator involvement is limited to adjusting the grinding plates on the Bico vertical grinder at the beginning of each preparation interval. Studies conducted using variable amounts of cleaning sand between grinding of samples indicate that the adjustment interval can be extended to 50 samples (25g cleaning sand) using an acceptance criteria of 80% of sample passing 80 mesh. the processed samples are suitable for direct geochemical analysis using a variety of standard chemical digestions. Cross contamination studies using s...

The stability of 57 consensus values in a proficiency test material re-issued blind after an interval of 18 years

In 2017 a silicate rock test material was re-issued in the geoanalytical proficiency test GeoPT after an interval of 18 years. The second distribution was participant-blind. Consensus values (for each analyte for which measurements were submitted by a sufficient number of participants) were compared and tested for significant difference in location. Such an experiment can provide information about the stability of both the test material and—the main focus of the present paper—the assigned values, which are consensus values as estimated location parameters. The validity of a consensus as an assigned value in proficiency testing has often been questioned in metrological thinking although there is seldom a practicable alternative. Over the whole suit of analytes, there was no indication of change in the location estimates. This is a remarkable finding, given the incidental changes that had occurred between the two rounds of the proficiency test, especially (a) changes in the analytical technology used, (b) the turnover in participant laboratories, and (c) the large increase in emphasis on data quality in the intervening period.

Using reference materials to improve the quality of data generated by USEPA analytical methods

The quality of data generated for the analysis of environmental samples is critical to State and Federal regulatory agencies to ensure that decisions based upon the amounts of contaminants in environmental samples are truly protective of public health. The quality and validation of these measurements using the approved analytical methodology could be significantly enhanced by incorporating certified reference materials as part of the quality control protocols, yet this has not been widely implemented. Data from certified reference materials can provide critical information that can impact assessments regarding data use that is unavailable by other means. Using the analysis of Cr(vi) in soil extracts as the test case, some of the issues surrounding the use of certified reference materials for environmental applications are discussed in this paper, including the relative cost, and the availability and applicability regarding element coverage and content.