: Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.

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A Compilation of Rate Parameters of Water-Mineral Interaction Kinetics for Application to Geochemical Modeling

The 1999 Regional Haze Rule provides a context for this review of visibility, the science that describes it, and the use of that science in regulatory guidance The scientific basis for the 1999 regulation is adequate The deciview metric that tracks progress is an imperfect but objective measure of what people see near the prevailing visual range The definition of natural visibility conditions is adequate for current planning, but it will need to be refined as visibility improves Emissions from other countries will set achievable levels above those produced by natural sources Some natural events, notably dust storms and wildfires, are episodic and cannot be represented by annual average background values or emission estimates Sulfur dioxide (SO2) emission reductions correspond with lower sulfate (SO4 2−) concentrations and visibility im-provements in the regions where these have occurred Non-road emissions have been growing more rapidly than emissions from other sources, which have remained

Visibility: Science and Regulation

Primary carbonates are a common feature of many modern and ancient lacustrine deposits. Carbonates from hydrologically open lakes show little or no correlation between δ13C and δ18O. In short-residence-time open lakes, carbonate oxygen isotopic composition is relatively invariant and typically is closely related to the bulk isotopic composition of inflow waters to the lake. Suites of carbonates which display covarying 13C and 18O compositions precipitate from waterbodies having relatively long residence times. Where the correlation between carbon and oxygen isotopic variations is high (r⪖ 0.7 ), the carbonates have normally precipitated from a closed lake. In addition, because of large changes in water balance, the δ18O of closed-lake carbonates usually varies over a range of several %o. Therefore, the combination of degree of covariance and spread of δ18O-values can be used to discriminate between carbonates produced in hydrologically open and closed basins. Within individual basins, covariant trends may have remarkable long-term persistence despite major environmental changes, indicating considerable stability in basin hydrology. Each closed lake has a unique isotopic identity defined by its covariant trend, which is a function of the basin's geographical and climatic setting, its hydrology, and the history of the waterbody. Any major interruption or realignment of this trend reflects a fundamental change in basin hydrology. Isotopic trends based upon the carbon and oxygen isotopic composition of primary lacustrine carbonates have several applications in palaeolimnology. The oxygen isotopic composition of open-lake carbonates may, with caution, be used as a proxy indicator of the composition of regional rainfall. Covariant trends can be used to trace the hydrological history of a basin, the evolution of individual water masses, and to correlate carbonate-bearing sediments from different parts of a basin.

A review of the palaeohydrological interpretation of carbon and oxygen isotopic ratios in primary lacustrine carbonates

Strontium isotopes as tracers of ecosystem processes: theory and methods

The incorporation of Mg2+ and Sr2+ into calcite overgrowths: influences of growth rate and solution composition

Strontium isotopic, chemical, and sedimentological evidence for the evolution of Lake Lisan and the Dead Sea

Strontium behavior in the aragonite-calcite transformation: An experimental study at 40–98°C

Oxygen isotope fractionation during the dolomitization of calcium carbonate

The origin and evolution of Canadian Shield brines: evaporation or freezing of seawater? New lithium isotope and geochemical evidence from the Slave craton

Amitai Katz

Papers

Strontium isotopic, chemical, and sedimentological evidence for the evolution of Lake Lisan and the Dead Sea

Strontium behavior in the aragonite-calcite transformation: An experimental study at 40–98°C

Oxygen isotope fractionation during the dolomitization of calcium carbonate

The origin and evolution of Canadian Shield brines: evaporation or freezing of seawater? New lithium isotope and geochemical evidence from the Slave craton

The geochemical evolution of the Pleistocene Lake Lisan-Dead Sea system