Departmental Papers (EES)

The mission of our department is to bring the time perspective of the Earth scientist to bear on contemporary problems of natural-resource conservation and environmental quality. We pursue this mission by exploring present and past interactions of processes that integrate the four terrestrial spheres: lithosphere, hydrosphere, atmosphere, and biosphere; by reconstructing the physical and biological history of our planet to provide a baseline for projection of observed trends into an uncertain future; and by educating future generations of environmental analysts, managers, and planners to exercise responsible stewardship of Earth and her natural resources.

 

 

Department of Earth and Environmental Science

Filters

96
93111
Reset filters

Settings

Search results

Now showing 1 - 10 of 96
  • Publication
    The Pulse of Calm Fan Deltas
    (2008-07-01) Kim, Wonsuck; Jerolmack, Douglas J
    At the heart of interpreting the history of Earth surface evolution preserved in the rock record is distinguishing environmental (allogenic) forcing from internally generated (autogenic) “noise.” Allogenic deposits classically have been recognized by their cyclic nature, which apparently results from periodic changes in base level, sediment supply, or tectonics. Autogenic deposits, which are quite variable in their origin and scale, are caused by the nonlinearity of sediment transport and might be expected to have a random or scale-free (fractal) signature. Here we describe a robust mechanism that generates cyclic deposits by an autogenic process in experimental fan deltas. Sheet flow over the fan surface induces deposition and an increase in fluvial slope and curvature to a point where the surface geometry is susceptible to a channelization instability, similar to channel initiation on hillslopes. Channelized flow results in incision and degrading of the fan surface to a lower slope, releasing a pulse of sediment that pushes the shoreline forward. Sheet flow resumes once the surface is regraded, and the cycle repeats in a surprisingly periodic fashion to produce cyclic foreset accretions. We use simple scaling and a one-dimensional fan evolution model to (1) demonstrate how time-varying flow width can cause pulses in sediment discharge at the shoreline in agreement with experiments and (2) reinterpret cyclic deposits reported in the field. Alternating sheet and channelized flows are known to operate on noncohesive fans in nature. Our results suggest that rather than reflecting variation in environmental forcing, many observed cyclic sedimentation packages may be a signature of the autogenic “pulse” of fan deltas under calm environmental conditions.
  • Publication
    Zirconolite: A Review of Localities Worldwide, and a Compilation of its Chemical Compositions
    (1996-06-01) Williams, C T; Gieré, Reto
    A compilation of the chemical data and brief review of the mineral zirconolite, essentially CaZrTi207, is presented. A total of 321 chemical analyses, 169 previously unpublished, from 39 of the 46 known terrestrial localities, and covering IO rock types are tabulated. A brief description of the minerals associated with zirconolite is outlined for each locality. Data from all zirconolite-bearing lunar rocks have also been compiled. The recently published nomenclature scheme for zirconolite is employed throughout.
  • Publication
    Retention of Actinides in Natural Pyrochlores and Zirconolites
    (1994) Lumpkin, Gregory R; Hart, K P; McGlinn, P J; Payne, T E; Gieré, Reto; Williams, C T
    Natural pyrochlore and zirconolite undergo a crystalline-aperiodic transformation caused by alpha-decay of 232Th and 2380 at dose levels between 2 X 1014 and 3 X 1017 a/mg. The principal effects of the transformation are volume expansion and microfracturing, providing potential pathways for fluids. Geochemical alteration of the minerals may occur under hydrothermal conditions or in low temperature, near surface environments, but Th and U usually remain immobile and can be retained for time scales up to 109 years. However, the Th-U isotope systematics of a zirconolite-bearing vein and dolomite host rock may provide evidence for disequilibrium between 230Th, 234U and 238U.
  • Publication
    Recalcitrant Pharmaceuticals in the Aquatic Environment: A Comparative Screening Study of Their Occurrence, Formation of Phototransformation Products and Their in Vitro Toxicity
    (2014-01-01) Bergheim, Marlies; Gminski, Richard; Spangenberg, Bernd; Dębiak, Malgorzata; Bürkle, Alexander; Mersch-Sundermann, Volker; Kümmerer, Klaus; Gieré, Reto
    Data allowing for a complete environmental risk assessment of pharmaceuticals and their photoderatives in the environment are still scarce. In the present study, in vitro toxicity and both bio- and photopersistence of various pharmaceuticals (aciclovir, allopurinol, cetirizine, cimetidine, fluconazole, hydrochlorothiazide, lisinopril, phenytoin, primidone, ranitidine, sotalol, sulpiride, tramadol and valsartane) as well as their phototransformation products were evaluated in order to fill data gaps and to help prioritise them for further testing. Twelve out of the fourteen compounds investigated were found to be neither readily nor inherently biodegradable in the Organisation of Economic Cooperation and Development-biodegradability tests. The study further demonstrates that the photo-induced transformation of the pharmaceuticals was faster upon irradiation with a Hg lamp (UV light) than with a Xe lamp emitting a spectrum that mimics sunlight. Comparing the non-irradiated with the respective irradiated solutions, a higher acute and chronic toxicity against bacteria was found for the irradiated solutions of seven compounds (cetirizine, cimetidine, hydrochlorothiazide, ranitidine, sulpiride, tramadol and valsartane). No cyto- and genotoxic effects were found in human cervical (HeLa) and liver (Hep-G2) cells for any of the investigated compounds or their phototransformation products. This comparative study documents that phototransformation products can arise as a result of UV treatment of wastewater containing these pharmaceuticals. It further demonstrates that some phototransformation products may have a higher environmental risk potential than the respective parent compounds because some phototransformation products exhibited a higher bacterial toxicity.
  • Publication
    Surface Crystal Chemistry of Phyllosilicates Using X-Ray Photoelectron Spectroscopy: A Review
    (2016-10-01) Elmi, Chiara; Guggenheim, Stephen; Gieré, Reto
    The characterization of freshly cleaved mica surfaces for surface structure and chemical composition was briefly reviewed and focused on surface crystal chemistry using X-ray photoelectron spectroscopy (XPS) and other surface-sensitive techniques. This paper considers micas, which are useful as a first approximation for the behavior of many clay surfaces. Emphasis was given to phyllosilicate XPS binding energies (''chemical shift''), which were described and used to obtain oxidation state, layer charge, and chemical bonding information from the chemical shifts of different peaks. The chemical shift of the Si2p binding-energy to lower values can result from a negative charge increase because of Si4+ replacement by Al3+ and/or Fe3+. The apparent interlayer coordination number reduction from twelve to eight at muscovite and tetraferri-phlogopite (001) surfaces was indicated by the XPS measured K2p binding-energy and is consistent with bond relaxation. Although chemical shifts are valuable to distinguish chemical bonding and oxidation state, chemical shifts usually cannot distinguish between different Al coordination environments where Al is in both tetrahedral and octahedral sites.
  • Publication
    Magnetite in the Human Body: Biogenic vs. Anthropogenic
    (2016-10-01) Gieré, Reto
    Magnetite is an iron-oxide mineral that occurs naturally on Earth. Because it is also an important component of many anthropogenic materials (e.g., coal fly ash) and synthetic products (e.g., black toner powders), magnetite can be released to the environment through human activities (1). In PNAS,Maher et al. (2) describe the abundant presence in the human brain of magnetite nanoparticles, some of which they attribute to air pollution. This finding could have major implications.
  • Publication
    How River Rocks Round: Resolving the Shape-Size Paradox
    (2014-02-12) Domokos, Gabor; Jerolmack, Douglas J; Sipos, Andras Á; Török, Ákos
    River-bed sediments display two universal downstream trends: fining, in which particle size decreases; and rounding, where pebble shapes evolve toward ellipsoids. Rounding is known to result from transport-induced abrasion; however many researchers argue that the contribution of abrasion to downstream fining is negligible. This presents a paradox: downstream shape change indicates substantial abrasion, while size change apparently rules it out. Here we use laboratory experiments and numerical modeling to show quantitatively that pebble abrasion is a curvature-driven flow problem. As a consequence, abrasion occurs in two well-separated phases: first, pebble edges rapidly round without any change in axis dimensions until the shape becomes entirely convex; and second, axis dimensions are then slowly reduced while the particle remains convex. Explicit study of pebble shape evolution helps resolve the shape-size paradox by reconciling discrepancies between laboratory and field studies, and enhances our ability to decipher the transport history of a river rock.
  • Publication
    Hydrodynamic and Suspended Sediment Transport Controls on River Mouth Morphology
    (2014-01-01) Falcini, Federico; Piliouras, Anastasia; Garra, Roberto; Guerin, Adrien; Jerolmack, Douglas J; Rowland, Joel; Paola, Chris
    River mouths building into standing bodies of water have strikingly varied growth habits. This presents a compelling pattern formation problem that is also of great practical relevance for subsurface prediction and managing coastal wetlands. Here we present a generalized 2.5-dimensional potential vorticity (PV) theory that explains sedimentation patterns of a sediment-laden stationary jet by coupling an understanding of vorticity with suspended sediment concentration fields. We explore the physical meaning of this new sediment-PV definition, and its impact on outflow depositional patterns, by analyzing data from a shallow wall-bounded plane jet experiment and by discussing new theoretical insights. A key result is that lateral advection and diffusion of suspended sediment are directly proportional to jet vorticity, a feature that reveals the mechanistic process that forms elongated channels by focused levee deposition. The new PV theory constitutes a more generalized mathematical framework that expands the Rouse theory for the equilibrium of suspended sediment.
  • Publication
    The Role of Th-U Minerals in Assessing the Performance of Nuclear Waste Forms
    (2014-10-01) Lumpkin, Gregory R; Gao, Yan; Gieré, Reto; Williams, C T; Mariano, Anthony; Geisler, Thorsten
    Materials designed for nuclear waste disposal include a range of ceramics, glass ceramics and glass waste forms. Those with crystalline phases have provided the momentum for studies of minerals as a means to understand aspects of waste-form crystal chemistry, behaviour in aqueous systems and radiation damage over geological periods of time. Although the utility of natural analogue studies varies, depending upon the degree of analogy to the proposed geological repository and other factors such as chemical composition, the available data suggest that Th-U host phases such as brannerite, monazite, pyrochlore, zircon and zirconolite are resistant generally to dissolution in aqueous fluids at low temperatures. Geochemical durability may or may not extend to hydrothermal systems depending on the specifics of fluid composition, temperature and pressure. At elevated temperatures, for example, davidite may break down to new phase assemblages including titanite, ilmenite and rutile. Perovskite is generally less resistant to dissolution at low temperatures and breaks down to TiO2, releasing A-site cations to the aqueous fluid. Studies of radiation damage indicate that the oxide and silicate phases become amorphous as a result of the gradual accumulation of alpha-recoil collision cascades. Monazite tends to remain crystalline on geological time scales, a very attractive property that potentially eliminates major changes in physical properties such as density and volume, thereby reducing the potential for cracking, which is a major concern for zircon. In spite of recent success in describing the behaviour of Th-U minerals in geological systems, considerable work remains in order to understand the P-T-X conditions during alteration and T-t history of the host rocks.
  • Publication
    The application of local and regional transfer functions to the reconstruction of Holocene sea levels, north Norfolk, England
    (2005-02-01) Horton, Benjamin P; Edwards, Robin J
    Foraminiferal assemblages from Thornham and Brancaster marshes (Norfolk, UK) illustrate statistically significant relationship with elevation with respect to the tidal frame. We develop local (data from Thornham and Brancaster marshes) and regional (data from Thornham and Brancaster marshes combined with those from 11 other sites around the UK) predictive foraminifera-based transfer functions to reconstruct former sea levels from a Holocene sediment sequence from Holkham, north Norfolk, UK. The two transfer functions produce similar patterns of tidal elevation change during the Holocene. The vertical error ranges of the local transfer function are smaller than those of the regional transfer function, although the difference (0.09 m) is not significant when compared to other factors affecting the reconstructed elevation. The value of the reconstructed elevations also differ between the two transfer functions (by up to 0.43 m), and this is primarily due to the lack of modern analogues in the local transfer function. We conclude that the reconstructions derived from the regional transfer function are more reliable than those of the local transfer function, since the latter achieves its slight increase in precision at the expense of a significant decrease in predictive power. The regional transfer function is used to construct a relative sea-level curve from fossil assemblages within a sediment core from north Norfolk, UK. These results are consistent with existing sea-level data and geophysical model predictions, and illustrate the utility of the foraminifera-based transfer function approach.