Geology Commons^™

Interaction Of Sea Ice Sediments And Surface Sea Water In The Arctic Ocean: Evidence From Excess 210Pb, M. Baskaran

Environmental Science and Geology Faculty Research Publications

We measured the activities of ²¹⁰Pb, ²²⁶Ra, ²³⁸U and ¹³⁷Cs in a suite of ice-rafted sediments (IRS) from the Arctic Ocean in an attempt to assess the interaction of sea ice sediments and surface water. The concentrations of these nuclides were compared to those of the benthic sediments in the coastal and shelf regions of the Arctic Ocean, which are believed to be the major source region for the IRS. The concentration factors (CF = activity of a nuclide in IRS/average activity in benthic sediments) are ∼1 and 4-92 for ¹³⁷Cs and ²¹⁰Pb, respectively. …

Comparison Of Two-Dimensional And Three-Dimensional Simulations Of Dense Nonaqueous Phase Liquids (Dnapls): Migration And Entrapment Of A Nonuniform Permeability Field, John A. Christ, Lawrence D. Lemke, Linda M. Abriola

Environmental Science and Geology Faculty Research Publications

The influence of reduced dimensionality (two-dimensional (2-D) versus 3-D) on predictions of dense nonaqueous phase liquid (DNAPL) infiltration and entrapment in statistically homogeneous, nonuniform permeability fields was investigated using the University of Texas Chemical Compositional Simulator (UTCHEM), a 3-D numerical multiphase simulator. Hysteretic capillary pressure–saturation and relative permeability relationships implemented in UTCHEM were benchmarked against those of another lab-tested simulator, the Michigan-Vertical and Lateral Organic Redistribution (M-VALOR). Simulation of a tetrachloroethene spill in 16 field-scale aquifer realizations generated DNAPL saturation distributions with approximately equivalent distribution metrics in two and three dimensions, with 2-D simulations generally resulting in slightly higher maximum …

Influence Of Hydraulic Property Correlation On Predicted Dense Nonaqueous Phase Liquid Source Zone Architecture, Mass Recovery And Contaminant Flux, Lawrence D. Lemke, Linda M. Abriola, John R. Lang

Environmental Science and Geology Faculty Research Publications

Organic liquid saturation distributions resulting from a simulated tetrachloroethene (PCE) spill were generated with alternative models of spatially varying aquifer properties for a statistically homogeneous, nonuniform sand aquifer. The distributions were analyzed to quantify DNAPL source zone characteristics and then incorporated as initial conditions for simulated PCE recovery using surfactant-enhanced aquifer remediation (SEAR). The predicted evolution of the spatial distribution of DNAPL saturations or source zone ‘‘architectures’’ and associated remediation efficiencies are strongly influenced by the spatial correlation of aquifer parameters and multiphase flow constitutive relationships. Model predictions suggest that removal of 60 to 99% of entrapped PCE can reduce …

Dense Nonaqueous Phase Liquid (Dnapl) Source Zone Characterization: Influence Of Hydraulic Property Correlation On Predictions Of Dnapl Infiltration And Entrapment, Lawrence D. Lemke, Linda M. Abriola, Pierre Goovaerts

Environmental Science and Geology Faculty Research Publications

The influence of aquifer property correlation on multiphase fluid migration and entrapment was explored through the use of correlated and uncorrelated porosity, permeability, and capillary pressure-saturation (P_c-Sat) parameter fields in a crosssectional numerical multiphase flow model. Data collected from core samples in a nonuniform sandy aquifer were used to generate three-dimensional aquifer parameter fields. Porosity was assumed to be uniform or simulated using sequential Gaussian simulation (SGS). Permeability (k) was modeled independently of porosity using SGS as well as simulated geostatistical indicator classes derived from measured grain size distribution curves. Retention characteristics were assigned employing Leverett …

Depositional Characteristics Of 7Be And 210Pb In Southeastern Michigan, D. Mcneary, M. Baskaran

Environmental Science and Geology Faculty Research Publications

The depositional fluxes in the bulk and dry fallout as well as the concentrations of ⁷Be and ²¹⁰Pb in aerosols were measured for a period of 17 months at Detroit, Michigan. The bulk depositional fluxes of ⁷Be and ²¹⁰Pb varied between 3.11 and 63.0 dpm cm⁻² yr⁻¹ (mean of 11.4 dpm cm⁻² yr⁻¹) and 0.35 and 10.3 dpm cm⁻² yr⁻¹ (mean of 1.41 dpm cm⁻² yr⁻¹), respectively, and this variability in the depositional fluxes is attributed to the frequency and amount of precipitation and seasonal variations …

Narrow Hybrid Zone Between Two Subspecies Of Big Sagebrush (Artemisia Tridentata: Aeteraceae). V. Soil Properties, Han Wang, David W. Byrd, Jeffrey L. Howard, E. Durant Mcarthur, John H. Graham, D. Carl Freeman

Environmental Science and Geology Faculty Research Publications

We studied soils of the big sagebrush (Artemisia tridentata) hybrid zone at two locations in Utah. The elemental composition, depth, and pH of soil in the basin and mountain big sagebrush habitats differed significantly from each other and from the hybrid zone soil. The hybrid zone soil is not just a simple blend of the two parental habitat soils. Rather, it possesses novel characteristics found in neither parental habitat and is more variable than the parental habitat soils. Correspondence analyses show that the sites occupied by each parental taxon are chemically distinct. Moreover, the principal axes from the two study …

Comments On “Measurements Of 7Be And 210Pb In Rain, Snow, And Hall”, M. Baskaran

Environmental Science and Geology Faculty Research Publications

No abstract available

A Search For The Seasonal Variability On The Depositional Fluxes Of 7Be And 210Pb, M. Baskaran

Environmental Science and Geology Faculty Research Publications

Investigations of the atmospheric fallout of ⁷Be and ²¹⁰Pb in many places around the globe indicate that there are seasonal variations on the depositional fluxes of these nuclides: high in winter in a few places, while in most places the high occurs in spring. However, these earlier studies did not address quantitatively the corresponding seasonal variations of the amount of precipitation during these periods. Data on the depositional fluxes of ⁷Be and ²¹⁰Pb in Galveston, Texas, during the years 1989–1991 indicate that the seasonal variation is not uniform from year to year, and the amount of …

Conglomerates Of The Upper Middle Eocene To Lower Miocene Sespe Formation Along The Santa Ynez Fault: Implications For The Geologic History Of The Eastern Santa Maria Basin Area, Jeffrey L. Howard

Environmental Science and Geology Faculty Research Publications

The depositional history of the Sespe Formation was studied using sedimentary facies analysis, clast counts, paleocurrent and clast morphological measurements, and petrographic methods. Sedimentation is interpreted to have occurred mainly as part of two depositional sequences in a coastal-braid-plain forearc-basin setting. Both sequences are present in the Santa Ynez Mountains, whereas only the upper sequence is recognized in the eastern Santa Maria basin. The lower sequence is part of a late middle to late Eocene sedimentary offlap attributed to a high input of terrigenous sediment derived mostly from the Mojave Desert region. This sequence is capped by an intraformational erosional …

Speleothems As Proxy For The Carbon Isotope Composition Of Atmospheric Co2, M. Baskaran, R. V. Krishnamurthy

Environmental Science and Geology Faculty Research Publications

We have measured the stable isotope ratios of carbon in a suite of recent cave deposits (<200 >years) from the San Saba County, Texas, USA. The methodology for dating these deposits using excess ²¹⁰Pb was recently established [Baskaran and Iliffe, 1993]. The carbon isotope ratios of these samples, spanning the time period ∼1800–1990 AD, reflect the carbon isotope ratio of atmospheric CO₂ for the same period. The pathways by which the δ¹³C of atmospheric CO₂ is imprinted on these speleothems can be explained using a model developed by Cerling (1984). The results suggest that the …

Atmospheric Depositional Fluxes Of 7Be And 210Pb At Galveston And College Station, Texas, M. Baskaran, Charles H. Coleman, Peter H. Santschi

Environmental Science and Geology Faculty Research Publications

The bulk depositional fluxes of ²¹⁰Pb and ⁷Be were measured at a coastal (Galveston) and an inland (College Station) station for about 3 years, between 1989 and 1991. The annual depositional fluxes of ⁷Be and ²¹⁰Pb at Galveston during this period varied by a factor of about 2.5, between 8.9 and 23.2 disintegrations per minute (dpm) cm⁻² yr⁻¹, with a mean of 14.7 dpm cm⁻² yr⁻¹ for ⁷Be, and 0.67 and 1.71 dpm cm⁻² yr⁻¹, with a mean of 1.03 dpm cm⁻² yr⁻¹ for ^{210 …}

Age Determination Of Recent Cave Deposits Using Excess 210Pb - A New Technique, M. Baskaran, Thomas M. Iliffe

Environmental Science and Geology Faculty Research Publications

Cave deposits have been widely used as proxy recorders in deciphering palaeoclimate during the last glacial/interglacial maxima (∼ 120 ka) [Harmon et al., 1975; Atkinson et al., 1978; Goede and Harmon, 1983; Ayliffe and Veeh, 1989]. Palaeoclimatic studies of cave deposits for the past 1–1000 yr time scale require a precise dating technique, that until now has been lacking. Due to the multiple sources of carbon in speleothems, ¹⁴C dates obtained for recently deposited calcite are highly variable and thus, ¹⁴C dating techniques are not suitable to obtain speleothem ages for the past 1–1000 years.

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Environmental Radiocesium In Subarctic And Arctic Alaska Following Chernobyl, M. Baskaran, J. J. Kelley, A. S. Naidu, D. F. Holleman

Environmental Science and Geology Faculty Research Publications

Radiocesium (¹³⁴ Cs and ¹³⁷ Cs) concentrations were measured in soil, plant and wildlife samples from subarctic to arctic Alaska. Concentrations of ¹³⁷ Cs ranged from below detectable or low levels in whale and fish samples to as high as 242 Bq/kg in lichen. For all potential human food items, the radiocesium concentrations measured in this study were below accepted permissible levels for human consumption. Chernobyl-derived radiocesium concentrations ranged from below detectable or low levels in all arctic samples (soil, sediment, lichen, whale, fish and caribou) to 32 Bq/kg in subarctic moss. Therefore the distribution and subsequent deposition of Chernobyl-derived …