There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.

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VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship

Reactive mass transport (RMT) simulation is a powerful numerical tool to advance our understanding of complex geochemical processes and their feedbacks in relevant subsurface systems. Thermodynamic equilibrium defines the baseline for solubility, chemical kinetics, and RMT in general. Efficient RMT simulations can be based on the operator-splitting approach, where the solver of chemical equilibria is called by the mass transport part for each control volume whose composition, temperature, or pressure has changed. Modeling of complex natural systems requires consideration of multiphase–multicomponent geochemical models that include nonideal solutions (aqueous electrolytes, fluids, gases, solid solutions, and melts). Direct Gibbs energy minimization (GEM) methods have numerous advantages for the realistic geochemical modeling of such fluid–rock systems. Substantial improvements and extensions to the revised GEM interior point method algorithm based on Karpov’s convex programming approach are described, as implemented in the GEMS3K C/C+ + code, which is also the numerical kernel of GEM-Selektor v.3 package (http://gems.web.psi.ch). GEMS3K is presented in the context of the essential criteria of chemical plausibility, robustness of results, mass balance accuracy, numerical stability, speed, and portability to high-performance computing systems. The stand-alone GEMS3K code can treat very complex chemical systems with many nonideal solution phases accurately. It is fast, delivering chemically plausible and accurate results with the same or better mass balance precision as that of conventional speciation codes. GEMS3K is already used in several coupled RMT codes (e.g., OpenGeoSys-GEMS) capable of high-performance computing.

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GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes

A general description of the mathematical and numerical formulations used in modern numerical reactive transport codes relevant for subsurface environmental simulations is presented. The formulations are followed by short descriptions of commonly used and available subsurface simulators that consider continuum representations of flow, transport, and reactions in porous media. These formulations are applicable to most of the subsurface environmental benchmark problems included in this special issue. The list of codes described briefly here includes PHREEQC, HPx, PHT3D, OpenGeoSys (OGS), HYTEC, ORCHESTRA, TOUGHREACT, eSTOMP, HYDROGEOCHEM, CrunchFlow, MIN3P, and PFLOTRAN. The descriptions include a high-level list of capabilities for each of the codes, along with a selective list of applications that highlight their capabilities and historical development.

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Reactive transport codes for subsurface environmental simulation

Recent developments in the area of biological detection by optical sensing of molecular oxygen (O2) are reviewed, with particular emphasis on the quenched-phosphorescence O2 sensing technique. Following a brief introduction to the main principles, materials and formats of sensor technology, the main groups of applications targeted to biological detection using an O2 transducer are described. These groups include: enzymatic assays; analysis of respiration of mammalian and microbial cells, small organisms and plants; food and microbial safety; monitoring of oxygenation in cell cultures, 3D models of live tissue, bioreactors and fluidic chips; ex vivo and in vivo O2 measurements; trace O2 analysis. For these systems, which enable a range of new bioanalytical tasks with different samples and models in a minimally invasive, contact-less manner, with high sensitivity, flexibility and imaging capabilities in 2D and 3D, relevant practical examples are presented and their merits and limitations discussed. An outlook of future scientific and technological developments in the field is also provided.

Biological detection by optical oxygen sensing

Enhancement of dilution and transverse reactive mixing in porous media: experiments and model-based interpretation.

Natural organic matter (NOM) can affect the behavior of arsenic within surface and subsurface environments. We used batch and column experiments to determine the effect of peat humic acids (PHA), groundwater fulvic acids (GFA), and a soil organic matter (SOM) extract on As sorption/transport in ferrihydrite-coated sand columns. A reactive transport model was used to quantitatively interpret the transport of As in flow-through column (breakthrough) experiments. We found that As(III) breakthrough was faster than As(V) by up to 18% (with OM) and 14% (without OM). The most rapid breakthrough occurred in systems containing SOM and GFA. Dialysis and ultrafiltration of samples from breakthrough experiments showed that in OM-containing systems, As was transported mostly as free (noncomplexed) dissolved As but also as ternary As-Fe-OM colloids and dissolved complexes. In OM-free systems, As was transported in colloidal form or as a free ion. During desorption, more As(III) desorbed (23-37%) than As(V) (10-16%), and SOM resulted in the highest and OM-free systems the lowest amount of desorption. Overall, our experiments reveal that (i) NOM can enhance transport/mobilization of As, (ii) different fractions of NOM are capable of As mobilization, and (iii) freshly extracted SOM (from a forest soil) had greater impact on As transport than purified GFA/PHA.

Influence of Natural Organic Matter on As Transport and Retention

Mass transfer, mixing, and therefore reaction rates during transport of solutes in porous media strongly depend on dispersion and diffusion. In particular, transverse mixing is a significant mechanism controlling natural attenuation of contaminant plumes in groundwater. The aim of the present study is to gain a deeper understanding of vertical transverse dispersive mixing of reaction partners in saturated porous media. Multitracer laboratory experiments in a quasi two-dimensional tank filled with glass beads were conducted and transverse dispersion coefficients were determined from high-resolution vertical concentration profiles. We investigated the behavior of conservative tracers (i.e., fluorescein, dissolved oxygen, and bromide), with different aqueous diffusion coefficients, in a range of grain-related Peclet numbers between 1 and 562. The experimental results do not agree with the classical linear parametric model of hydrodynamic dispersion, in which the transverse component is approximated as the su...

Evidence of compound-dependent hydrodynamic and mechanical transverse dispersion by multitracer laboratory experiments.

Enhanced biodegradation by hydraulic heterogeneities in petroleum hydrocarbon plumes

In this study, we performed multitracer laboratory bench-scale experiments and pore-scale simulations in different homogeneous saturated porous media (i.e., different grain sizes) with the objective of (i) obtaining a generalized parameterization of transverse hydrodynamic dispersion at the continuum Darcy scale; (ii) gaining an improved understanding of the role of basic transport processes (i.e., advection and molecular diffusion) at the subcontinuum scale and their effect on the macroscopic description of transverse mixing in porous media; (iii) quantifying the importance of compound-specific properties such as aqueous diffusivities for transport of different solutes. The results show that a non-linear compound-dependent parameterization of transverse hydrodynamic dispersion is required to capture the observed lateral displacement over a wide range of seepage velocities (0.1–35 m/day). With pore-scale simulations, we can prove the hypothesis that the interplay between advective and diffusive mass transfer results in vertical concentration gradients leading to incomplete mixing in the pore channels. We quantify mixing in the pore throats using the concept of flux-related dilution index and show that different solutes undergoing transport in a flow-through system with a given average velocity can show different degrees of incomplete mixing. Furthermore, it is this compound-specific incomplete mixing within pores that causes different local transverse (mechanical) dispersion to result at the Darcy scale for high flow velocities. We conclude that physical processes at the microscopic level significantly determine the observed macroscopic behavior and, therefore, should be properly reflected in up-scaled parameterizations of transport processes such as local hydrodynamic dispersion coefficients.

Massimo Rolle

Papers

Enhancement of dilution and transverse reactive mixing in porous media: experiments and model-based interpretation.

Influence of Natural Organic Matter on As Transport and Retention

Evidence of compound-dependent hydrodynamic and mechanical transverse dispersion by multitracer laboratory experiments.

Enhanced biodegradation by hydraulic heterogeneities in petroleum hydrocarbon plumes

Experimental Investigation and Pore-Scale Modeling Interpretation of Compound-Specific Transverse Dispersion in Porous Media