Water in the deep Earth: The dielectric constant and the solubilities of quartz and corundum to 60 kb and 1200 °C

Application of multivariate statistical methods and inverse geochemical modeling for characterization of groundwater — A case study: Ain Azel plain (Algeria)

Sulfide minerals precipitate from hydrothermal solution where their constituent metals and sulfide are more stable residing in the solid than in aqueous solution. An understanding of how and why sulfide minerals precipitate means understanding what chemical species hold metals and sulfide in solution, and what fundamental chemical and physical processes may liberate those reactants to precipitate in solids–processes such as pH increase, chemical reduction, dilution or cooling.

In the natural setting, the fundamental chemical and physical drivers of sulfide precipitation are a response to a wide range of processes. For example, pH increases where acidic hydrothermal fluids react with feldspars or carbonates in wall rocks, or where a hydrothermal fluid boils out CO2 to the gas phase. The pH also increases where a brine is diluted by fresh water while maintaining equilibrium with a silicate wall-rock assemblage. Cooling follows from isoenthalpic boiling, which is caused by pressure drop as a fluid ascends in a hydrothermal system. Cooling also results from dilution by cold water or from heat conduction into cold wall rocks. Chemical reduction occurs where an oxidized fluid reacts with carbon or methane or ferrous iron.

In this chapter, we explore the fundamental chemical and physical processes that drive sulfide mineral dissolution and precipitation as well as a limited set of more complex processes that control the fundamental drivers. The basic goal is to understand the chemistry of the simplest processes so as to improve our ability to deduce what actually happens in the natural world. Our basic approach is to run thermodynamic calculations of whole-system models of the processes causing sulfide precipitation and dissolution—models that take into account simultaneous equilibria involving assemblages of minerals at chemical equilibrium among themselves and with hundreds of aqueous species. We then interpret the models in terms of fundamental effects of pH …

Sulfide Mineral Precipitation from Hydrothermal Fluids

In summer (pre-monsoon) of recent years, low water level among the last few decades, has been observed in several lower Indian reaches of the Ganges (or Ganga) river (with estimated river water level depletion rates at the range of −0.5 to −38.1 cm/year between summers of 1999 and 2013 in the studied reaches). Here, we show this Ganges river depletion is related to groundwater baseflow reduction caused by ongoing observed groundwater storage depletion in the adjoining Gangetic aquifers (Ganges basin, −0.30 ± 0.07 cm/year or −2.39 ± 0.56 km3/year). Our estimates show, 2016-baseflow amount (~1.0 × 106 m3/d) has reduced by ~59%, from the beginning of the irrigation-pumping age of 1970s (2.4 × 106 m3/d) in some of the lower reaches. The net Ganges river water reduction could jeopardize domestic water supply, irrigation water requirements, river transport, ecology etc. of densely populated northern Indian plains. River water reduction has direct impact on food production indicating vulnerability to more than 100 million of the population residing in the region. The results of this study could be used to decipher the groundwater-linked river water depletion as well as the regional water security in other densely populated parts of the globe.

/pdf/groundwater-depletion-causing-reduction-of-baseflow-u2bv5sp9pp.pdf

Groundwater depletion causing reduction of baseflow triggering Ganges river summer drying

In situ feldspar dissolution rates in an aquifer

This paper presents a modeling analysis of the geochemical evolution of a contaminated sandy aquifer at a uranium mill tailings site in the western United States. The tailings pond contains fluids having a pH of 1.5 to 3.5 and high levels of As, Be, Cd, Cr, Pb, Mo, Ni, Se, 226Ra, 228Ra, 230Th, 238U, and 234U. Seepage of tailings fluids into the aquifer has formed a low-pH ground water plume. The reclamation plan is to install a low-permeability cover on the tailings pond to stop the seepage and allow the plume to be attenuated by reactions with the aquifer matrix and flushed by uncontaminated upgradient ground water. To evaluate this reclamation scenario, ground water and sediment core samples were analyzed along one flowpath. Speciation-solubility and mass-transfer modeling revealed two sets of chemical reactions for acid seepage and flushing, respectively. The current concentrations and distribution of ground water constituents can be interpreted as being controlled by stepwise pH-buffer reactions with calcite, amorphous aluminum hydroxide, and amorphous iron hydroxides. These buffer reactions divide the aquifer into zones of near-constant pH, separated by interface zones. For the flushing stage, it is predicted that reactions with surface-bound species will dominate the reaction paths, and more pore volumes are required to neutralize the plume than predicted by models that do not consider surface reactions. Direct mineralogical and surface analysis is needed to substantiate this assertion.

Natural attenuation reactions at a uranium mill tailings site, western U.S.A.

Functionalized epigallocatechin gallate copolymer inhibit dentin matrices degradation: Mechanical, solubilized telopeptide and proteomic assays.

Thermodynamics deals with energy levels and energy transfers between states of matter, and is therefore fundamental to all branches of science. This new edition provides an accessible introduction to the subject, specifically tailored to the interests of Earth and environmental science students. Beginning at an elementary level, the first four chapters explain all necessary concepts via a simple graphical approach. Throughout the rest of the book, the author emphasizes the importance of field observations and demonstrates that, despite being derived from idealized circumstances, thermodynamics is crucial to understanding ore formation, acid mine drainage, and other real-world geochemical and geophysical problems. Exercises now follow each chapter, with answers provided at the end of the book. An associated website includes extra chapters and password-protected answers to additional problems. This textbook is ideal for undergraduate and graduate students studying geochemistry and environmental science.

Thermodynamics of Natural Systems: Theory and Applications in Geochemistry and Environmental Science

Reaction Path Modeling

Computer Programs for Geochemical Modeling

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