The Sensitivity of Four Monitoring Well Sampling Systems to Low Concentrations of Three Volatile Organics

Four state-of-the-art ground water sampling systems were analyzed to determine their reliability in providing representative samples of the volatile chlorinated hydrocarbons trichloroethylene (TCE), perchloroethylene (PCE), and 1,1,1-trichloroethane (TCA) from a simulated monitoring well. The sampling systems studied represent four commonly used devices, including a stainless steel and Teflon® piston pump, a Teflon bailer, a Teflon bladder pump, and a PVC air-lift pump.
Controlled laboratory sampling experiments were conducted in a tank and well test chamber designed to approximate field conditions. A well purging and sampling procedure was used in the test apparatus to determine the accuracy and precision of each device for detecting low concentrations of the compounds in ground water. The compounds selected are some of the most ubiquitous hazardous contaminants found in shallow aquifers near hazardous waste sites throughout the United States.
No significant statistical difference was found among the four sampling systems in detecting the compounds.     

Infrared spectroscopic investigation of hydroxyl in β-(Mg,Fe)2SiO4 and coexisting olivine: Implications for mantle evolution and dynamics

Wadsleyite (β-(Mg,Fe)₂SiO₄) is a major constituent of the Earth's transition zone and is known to accommodate OH. The portion of the transition zone between 400–550 km could be an important source or sink for hydroxyl in plumes and slabs intersecting this region. Micro-infrared spectroscopy has been carried out on the β-phase and coexisting metastable olivine synthesized in a multianvil apparatus at 14 GPa and 1550–1650 K under hydrous conditions. Single-crystal and polycrystal specimens of both phases were analyzed in the 1800–8500 cm^?1 frequency region to determine the speciation, abundances, and partitioning behavior of the hydrous components in coexisting β-phase and olivine. β-phase spectra consistently show three distinct OH bands at 3329, 3580, and 3615 cm^?1. OH concentrations range from 10000–65000 H/10⁶ Si. A strong positive correlation of grain size and extent of transformation with OH concentration in the β-phase indicates that grain-growth and transformation rates are enhanced in a hydrous environment. Olivine spectra are variable, but consistently show a prominent broad-band absorbance representing molecular H₂O, consistent with the infrared signature of the starting material. OH concentrations in olivine range from <300–1400 H/10⁶ Si. The highest OH concentrations measured for olivine and the β-phase may represent solubility limits, in which case the OH solubility ratio between these two phases is approximately 1∶40. Where both phases coexist and are undersaturated with OH, the partitioning ratio of OH between them is about 1∶100. The large solubility contrast between olivine and the β-phase suggests a mechanism for hydrating the transition zone via olivine carried down in subducting slabs. Plumes impinging on an OH-rich upper transition region could cause H₂ or H₂O to be released upon transformation of the β-phase to olivine, resulting in initiation of secondary upwellings. If dissolution of OH weakens the β-phase, and if OH is present in the mantle, the region between 400–550 km could be a zone of low viscosity.     

Petrology of fibrous coal (fusain) and associated inertinites from the Early Paleocene of the central Alberta Plains

Megascopic, micropetrographic and scanning-electron microscopic investigations of fibrous coal indicate that paleo-wildfires were common occurrences in the mire which produced Highvale coals. At least 20 fibrous coal (fusain) horizons have been identified in corehole samples from the pit no. 3 locality at Highvale, in the central Alberta Plains. Thicknesses of individual horizons vary, and are not particular to any stratigraphic position within coal seams. The majority of these fibrous horizons is within the two thick economic seams, the Highvale Nos. 1 and 2, which are characteristically megascopically dull. The dullness of given lithotypes is largely related to inertinite content with fibrous coal containing 51% inertinite on average, and selected horizons comprised of as much as 85% inertinite. Semifusinite and inertodetrinite are the predominant inertinites, with a few horizons exhibiting highly reflecting fusinite. Macrinite is rare, and micrinite is absent. SEM investigations reveal that certain fibrous coals exhibit excellent preservation of the original gymnospermous (Taxodium) woody tissue. Features such as homogenization and swelling of the cell walls, elimination of the middle lamellae, and preservation of bordered pits are clearly indicative of charcoal formation as a product of paleo-wildfires. Depending upon the nature of the fire, temperatures obtained and the nature of the mire vegetation, a wide range of inertinite precursors can be produced.     

Late Pleistocene Vertebrates and Other Fossils from Epiguruk, Northwestern Alaska

Sediments exposed at Epiguruk, a large cutbank on the Kobuk River about 170 km inland from Kotzebue Sound, record multiple episodes of glacial-age alluviation followed by interstadial downcutting and formation of paleosols. Vertebrate remains from Epiguruk include mammoth, bison, caribou, an equid, a canid, arctic ground squirrel, lemmings, and voles. Radiocarbon ages of bone validated by concordant ages of peat and wood span the interval between about 37,000 and 14,000 yr B.P. The late Pleistocene pollen record is dominated by Cyperaceae, with Artemisia, Salix, Betula, and Gramineae also generally abundant. The fossil record from Epiguruk indicates that the Kobuk River valley supported tundra vegetation with abundant riparian willows during middle and late Wisconsin time. Large herbivores were present during the height of late Wisconsin glaciation as well as during its waning stage and the preceding interstadial interval. The Kobuk River valley would have been a favorable refugium for plants, animals, and possibly humans throughout the last glaciation.     

A Raman spectroscopic study of H/D isotopically substituted hydrous aluminosilicate glasses

We have obtained high quality Raman spectra for two H/D isotopically substituted hydrous aluminosilicate glasses with compositions along the NaAlSi₃O₈-SiO₂ join. Consistent with the results of previous studies, the isotope shift for the band near 900 cm^–1, whose intensity grows with increasing water content, is extremely small: v _h /v _d = 1.004 ± 0.004. The lack of a definite H/D isotope shift for this band does not, however, preclude its association with a vibration of a hydrous species in the glass, because of likely strong coupling between different vibrational modes of hydrated framework species. The 900 cm^–1 band could well be due to a T — OH (T = Si, Al) stretching or bending vibration in the hydrous glass, as required by the presence of a combination band near 4500 cm^–1 in near-infrared spectra.     

Effect of Concentration on Sorption of Dissolved Organics by PVC, PTFE, and Stainless Steel Well Casings

This report examines sorption of low ppb levels of organic solutions by polytetra- fluoroethylene (PTFE), rigid polyvinyl chloride (PVC), and stainless steel 304 and 316 well casings. Nineteen organics were selected, including several munitions and chlorinated solvents. Compounds were selected to offer a range of physical properties, such as solubility in water, octanol/water partition coefficient, and molecular structure. When these results were compared with the results from a similar study conducted at ppm levels, the rate and extent of sorption by PTFE and PVC were the same as seen previously for almost all analytes. There were no losses of any compounds associated with stainless steel. At these low levels (ppm and ppb), the rate of diffusion within the polymer (PVC and PTFE) is independent of concentration. Only with PTFE are the rates rapid enough to be of concern when monitoring for some contaminants in ground water. Tetrachloroethylene was the compound PTFE sorbed the most rapidly. The study showed that PVC well casings are suitable for monitoring low levels (ppm and ppb) of organics.     

PHYSICAL GEOGRAPHY OF TROPICAL LATIN AMERICA: THE SPATIAL AND TEMPORAL HETEROGENEITY OF ENVIRONMENTS

For the past 40 years, studies of physical geography in tropical Latin America have concentrated on the spatial and temporal diversity of biophysical environments and biota. Environmental heterogeneity arises from historical and present-day interaction between climatic, geomorphologic, edaphic, and biogeographic systems. Recent research emphasizes three major themes involving these systems: Quaternary climate change; human-altered biophysical environments; and geomorphologic activity. Findings on these themes are evaluated with respect to the tropical highlands, the tropical lowlands and related extra-tropical areas. Research on physical geography in Latin America promises numerous contributions toward a better understanding of environmental conservation.