Exploring weathering and regolith transport controls on Critical Zone development with models and natural experiments     

Suzanne P. Anderson  Robert S. Anderson  Eve-Lyn S. Hinckley  Patrick Kelly  Alex Blum 《Applied Geochemistry》2011

The architecture of the Critical Zone, including mobile regolith thickness and depth to the weathering front, is first order controlled by advance of a weathering front at depth and transport of sediment at the surface. Differences in conditions imposed by slope aspect in the Gordon Gulch catchment of the Boulder Creek Critical Zone Observatory present a natural experiment to explore these interactions. The weathering front is deeper and saprolite more decayed on north-facing than on south-facing slopes. Simple numerical models of weathering front advance, mobile regolith production, and regolith transport are used to test how weathering and erosion rates interact in the evolution of weathered profiles. As the processes which attempt are being made to mimic are directly tied to climate variables such as mean annual temperature, the role of Quaternary climate variation in governing the evolution of Critical Zone architecture can be explored with greater confidence.  相似文献   

Swelling of Clay-Sulfate Rocks: A Review of Processes and Controls     

Christoph Butscher  Thomas Mutschler  Philipp Blum 《Rock Mechanics and Rock Engineering》2016,49(4):1533-1549

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Oxygen isotope evolution of the Lake Owyhee volcanic field,Oregon, and implications for the low-δ18O magmatism of the Snake River Plain–Yellowstone hotspot and other low-δ18O large igneous provinces     

Tyler B. Blum  Kouki Kitajima  Daisuke Nakashima  Ariel Strickland  Michael J. Spicuzza  John W. Valley 《Contributions to Mineralogy and Petrology》2016,171(11):92

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Book reviews     

Richard F. Dame  John P. Harrington  Alan G. Heath  Linda Blum  Julie W. Ambler 《Estuaries and Coasts》1998,21(3):500-503

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A sequential extraction to determine the distribution of apatite in granitoid soil mineral pools with application to weathering at the Hubbard Brook Experimental Forest,NH, USA     

Carmen A. Nezat  Joel D. Blum  Ruth D. Yanai  Steven P. Hamburg 《Applied Geochemistry》2007

Mineral weathering in soils is an important source of many nutrients to forest ecosystems. Apatite, a Ca phosphate mineral, occurs in trace amounts in virtually all igneous and metamorphic rocks and is often found as small mineral inclusions in more weathering-resistant silicate minerals. To better understand the distribution of apatite in soils and its exposure to soil solutions, a sequential extraction method was developed to selectively dissolve minerals from soils so that the amount of apatite in contact with soil solutions versus that armored by silicate minerals could be quantified. The use of three molarities of HNO₃ (0.01, 0.1 and 1 M) at three temperatures (0, 10, or 20 °C) was explored and it was found that apatite congruently dissolved in 1 M HNO₃ at all three temperatures, but did not completely dissolve in weaker HNO₃ solutions. Soil horizons, glacial till (i.e., soil parent material), and individual minerals separated from till collected from the Hubbard Brook Experimental Forest (HBEF), NH, were subjected to a 4-step sequential extraction. Chemical analyses of the extracts indicate that 1 M NH₄Cl (pH 7; 20 °C) removes exchangeable ions, 1 M HNO₃ at 20 °C primarily dissolves apatite in contact with solutions, 1 M HNO₃ at 200 °C primarily dissolves biotite and chlorite (and apatite armored by them), and a mixture of concentrated HNO₃, HCl, and HF at 200 °C dissolves the more refractory minerals including muscovite, alkali feldspar, plagioclase feldspar and quartz (and apatite armored by these minerals). This extraction method was applied to soil profiles from HBEF to demonstrate that it could be used to interpret the abundance of apatite and other minerals as a function of depth. Approximately 70% of the apatite in the HBEF soil parent material is exposed to soil solutions; the remaining 30% is armored in more weathering-resistant micas and feldspars. In the upper soil horizons, the only apatite that has not been weathered from the soil occurs as inclusions in micas and feldspars and thus the rate of dissolution of apatite in weathered soil horizons is controlled by silicate mineral dissolution.  相似文献   

Controls on soil pore water solutes: An approach for distinguishing between biogenic and lithogenic processes     

Art F. White  Marjorie S. Schulz  Davison V. Vivit  Alex E. Blum  David A. Stonestrom 《Journal of Geochemical Exploration》2006,88(1-3):363

Spatial and temporal variations in pore water compositions are characterized for a deep regolith profile developed on a marine terrace chronosequence near Santa Cruz California. Variations are resolved in terms of the dominance of either a lithogenic process, i.e. chemical weathering, or a biogenic process, i.e. plant nutrient cycling. The concept of elemental fractionation is introduced describing the extent that specific elements are mobilized and cycled as a result of these processes.  相似文献   

Comments on stubbe's deviations from the barometric law     

Peter W. Blum 《Planetary and Space Science》1974,22(1):183-186

An approximation for the height distribution of nitrogen and atomic oxygen in the thermosphere between 120 and 500 km is obtained by the assumption that these constituents are in diffusive equilibrium. The horizontal wind system in the thermosphere may cause deviations from the diffusive equilibrium distribution due to the non-zero divergence of the horizontal flow and the vertical mass motion associated with it. Stubbe has examined this problem and deduced considerable deviations from diffusive equilibrium due to this effect. The problem is re-examined here, and it is shown that there exist arguments that the deviations from diffusive equilibrium due to horizontal wind fields are not as large as suggested by Stubbe.  相似文献   

A representation of Jacchia's thermospheric models in spherical harmonic functions     

P. Blum  I. Harris 《Planetary and Space Science》1974,22(6):955-960

The Jacchia models are represented in terms of spherical harmonic functions. This representation has the advantage of ease of comparison with other global theoretical and empiric models that use this mathematical form. Furthermore it is analytic, continuous and has continuous derivatives all over the globe. The representation of the exospheric temperatures shows clearly the amplitudes of the various periodic terms and uses relatively few constants. An example of a similar representation for the total mass density at a particular height and level of solar activity is given as well.  相似文献   

Neutral gases of interstellar origin in interplanetary space     

P.W. Blum  J. Pfleiderer  C. Wulf-Mathies 《Planetary and Space Science》1975,23(1):93-105

The distribution of interplanetary neutral gases of interstellar origin is recalculated. Several improvements over earlier solutions of the problem are presented. This is especially true for the upwind and the downwind axes, which are of importance in the analysis of the observations of the back-scattered solar resonance radiation.  相似文献   

Molecular mechanics and quantum mechanical modeling of hexane soot structure and interactions with pyrene     

JD Kubicki 《Geochemical transactions》2000,1(1):41-6

Molecular simulations (energy minimizations and molecular dynamics) of an n-hexane soot model developed by Smith and co-workers (M. S. Akhter, A. R. Chughtai and D. M. Smith, Appl. Spectrosc., 1985, 39, 143; ref. 1) were performed. The MM+ (N. L. Allinger, J. Am. Chem. Soc., 1977, 395, 157; ref. 2) and COMPASS (H. Sun, J. Phys. Chem., 1998, 102, 7338; ref. 3) force fields were tested for their ability to produce realistic soot nanoparticle structure. The interaction of pyrene with the model soot was simulated. Quantum mechanical calculations on smaller soot fragments were carried out. Starting from an initial 2D structure, energy minimizations are not able to produce the observed layering within soot with either force field. Results of molecular dynamics simulations indicate that the COMPASS force field does a reasonably accurate job of reproducing observations of soot structure. Increasing the system size from a 683 to a 2732 atom soot model does not have a significant effect on predicted structures. Neither does the addition of water molecules surrounding the soot model. Pyrene fits within the soot structure without disrupting the interlayer spacing. Polycyclic aromatic hydrocarbons (PAH), such as pyrene, may strongly partition into soot and have slow desorption kinetics because the PAH-soot bonding is similar to soot–soot interactions. Diffusion of PAH into soot micropores may allow the PAH to be irreversibly adsorbed and sequestered so that they partition slowly back into an aqueous phase causing dis-equilibrium between soil organic matter and porewater.  相似文献