Rate constants of dissolution derived from the measurements of mass balance in hydrological catchments

Pačes, T.

doi:10.1016/0016-7037(83)90202-8

Cited by 206 publications

(88 citation statements)

References 8 publications

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“…In each case the major source of the cations was thought to be the terrestrial watershed. Evidence from the Elbe River watershed suggests that anthropogenic acidification caused in part by acidic deposition resulted in an increase in cation weathering (Paces 1983). Henriksen (1982) found that the ratio of the increase in cation equivalents in lakes in Norway to the sulfate due to acid precipitation was 0.4 and surmised that the cation increase was caused by terrestrial processes.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of hydrogen ion neutralization in an experimentally acidified lake

Cook

Kelly

Schindler

et al. 1986

Limnology & Oceanography

179

114

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The experimental acidification of Lake 223 (Experimental Lakes Area, northwestern Ontario) with sulfuric acid in 1976-1983 allowed a detailed examination of the capacity of the lake to neutralize hydrogen ion. A whole-lake alkalinity and ion budget for Lake 223 showed that 66-81% of the added sulfuric acid was neutralized by alkalinity production in the lake. Nearly 85% of in situ alkalinity production was accounted for by net loss of sulfate through bacterial sulfate reduction, coupled with iron reduction and iron sulfide formation, in littoral sediments (60%) and in the hypolimnion (25%). Exchange of hydrogen ion for calcium and manganese in the sediments accounted for 19% of the alkalinity generated, while other cations were net sinks for alkalinity. Alkalinity input from the watershed of Lake 223 was very small, averaging about 5% of that produced in the lake.The seasonal production of 1,000 peq liter-* alkalinity in the anoxic hypolimnion of this softwater lake could be attributed to bacterial sulfate reduction coupled with iron sulfide formation, ammonium production, and iron (II) production. Only the alkalinity produced from bacterial sulfate reduction coupled with iron sulfide formation remained throughout the annual cycle.

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Section: Discussionmentioning

confidence: 99%

Mechanisms of hydrogen ion neutralization in an experimentally acidified lake

Cook

Kelly

Schindler

et al. 1986

Limnology & Oceanography

179

114

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“…Papers on natural feldspars include: crystallographic control on alteration of microcline perthite (33); formation of pits aligned along microcracks and twin planes, enlargement into honeycombs, and major increase in surface area per volume (34-38; forthcoming papers by M. Lee and I. Parsons); slower dissolution of natural than artificially weathered feldspars at comparable pH, etc., and absence of a protective surface layer of common weathering products (35,(39)(40)(41)(42)(43); interaction of feldspar minerals in soils with organic species and microbes (44)(45); and various geological factors for feldspars in sedimentary rocks (46)(47)(48).…”

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confidence: 99%

Atmospheric weathering and silica-coated feldspar: Analogy with zeolite molecular sieves, granite weathering, soil formation, ornamental slabs, and ceramics

Smith

1998

Proc. Natl. Acad. Sci. U.S.A.

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Feldspar surfaces respond to chemical, biological, and mechanical weathering. The simplest termination is hydroxyl (OH), which interacts with any adsorption layer. Acid leaching of alkalis and aluminum generated a silica-rich, nanometers-thick skin on certain feldspars. Natural K, Nafeldspars develop fragile surfaces as etch pits expand into micrometer honeycombs, possibly colonized by lichens. Most crystals have various irregular coats. Based on surfacecatalytic processes in molecular sieve zeolites, I proposed that some natural feldspars lose weakly bonded Al-OH (aluminol) to yield surfaces terminated by strongly bonded Si-OH (silanol). This might explain why some old feldspar-bearing rocks weather slower than predicted from brief laboratory dissolution. Lack of an Al-OH infrared frequency from a feldspar surface is consistent with such a silanol-dominated surface. Raman spectra of altered patches on acid-leached albite correspond with amorphous silica rather than hydroxylated silica-feldspar, but natural feldspar may respond differently. The crystal structure of H-exchanged feldspar provides atomic positions for computer modeling of complex ideas for silica-terminated feldspar surfaces. Natural weathering also depends on swings of temperature and hydration, plus transport of particles, molecules, and ionic complexes by rain and wind. Soil formation might be enhanced by crushing granitic outcrops to generate new Al-rich surfaces favorable for chemical and biological weathering. Ornamental slabs used by architects and monumental masons might last longer by minimizing mechanical abrasion during sawing and polishing and by silicifying the surface. Silica-terminated feldspar might be a promising ceramic surface.Chemical and physical changes in minerals underlie many aspects of human welfare. Agriculture depends on the interaction of soils with water, ionic and molecular species, and biological organisms. The weathering of feldspar minerals (1-4) from bedrock into clays is important for the production of food. Many laboratory experiments have measured the dissolution rate of feldspar minerals by water containing a wide range of ionic and molecular species, including organic acids relevant to biological weathering. Data are available for the range of feldspar chemistry from strongly acid to alkaline conditions (2, 3). Electron and chemical microscopy of feldspar surfaces is revealing a wealth of information on chemical and physical changes, including pitting, honeycombing, and selective dissolution (5). Only scattered data are available for the rate of weathering of feldspars in natural watersheds, but they indicate that natural atmospheric weathering of many rocks is slower than for short term laboratory experiments of crushed samples (2, 3). Casual examination of granite slabs in cemeteries and city buildings indicates that the alkali feldspars are weathering slowly unless mechanical spalling is occurring.

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“…What has prompted us to re-examine this hypothesis proposed nearly half a century ago is its current relevance to the interpretation of the well known and extensively discussed apparent discrepancy between the field derived feldspar dissolution rates and those measured in the laboratory (Paces, 1983;Velbel, 1990;Brantley, 1992;Blum and Stillings, 1995;Drever and Clow, 1995;White and Brantley, 2003;Zhu, 2005; and references therein), which currently is under intense and active research. In general, field derived feldspar dissolution rates are two to five orders of magnitude slower than laboratory measured rates (ibid).…”

Section: Introductionmentioning

confidence: 99%

Alkali feldspar dissolution and secondary mineral precipitation in batch systems: 3. Saturation states of product minerals and reaction paths

Zhu¹,

Lü²

2009

Geochimica et Cosmochimica Acta

113

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In order to evaluate the complex interplay between dissolution and precipitation reaction kinetics, we examined the hypothesis of partial equilibria between secondary mineral products and aqueous solutions in feldspar-water systems. Speciation and solubility geochemical modeling was used to compute the saturation indices (SI) for product minerals in batch feldspar dissolution experiments at elevated temperatures and pressures and to trace the reaction paths on activity-activity diagrams. The modeling results demonstrated: (1) the experimental aqueous solutions were supersaturated with respect to product minerals for almost the entire duration of the experiments; (2) the aqueous solution chemistry did not evolve along the phase boundaries but crossed the phase boundaries at oblique angles; and (3) the earlier precipitated product minerals did not dissolve but continued to precipitate even after the solution chemistry had evolved into the stability fields of minerals lower in the paragenesis sequence. These three lines of evidence signify that product mineral precipitation is a slow kinetic process and partial equilibria between aqueous solution and product minerals were not held. In contrast, the experimental evidences are consistent with the hypothesis of strong coupling of mineral dissolution/precipitation kinetics [e.g., Zhu C., Blum A. E. and Veblen D. R. (2004a) Feldspar dissolution rates and clay precipitation in the Navajo aquifer at Black Mesa, Arizona, USA. In Water-Rock Interaction (eds. R. B. Wanty and R. R. I. Seal). A.A. Balkema, Saratoga Springs,. In all batch experiments examined, the time of congruent feldspar dissolution was short and supersaturation with respect to the product minerals was reached within a short period of time. The experimental system progressed from a dissolution driven regime to a precipitation limited regime in a short order. The results of this study suggest a complex feedback between dissolution and precipitation reaction kinetics, which needs to be considered in the interpretation of field based dissolution rates.

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Rate constants of dissolution derived from the measurements of mass balance in hydrological catchments

Cited by 206 publications

References 8 publications

Mechanisms of hydrogen ion neutralization in an experimentally acidified lake

Mechanisms of hydrogen ion neutralization in an experimentally acidified lake

Atmospheric weathering and silica-coated feldspar: Analogy with zeolite molecular sieves, granite weathering, soil formation, ornamental slabs, and ceramics

Alkali feldspar dissolution and secondary mineral precipitation in batch systems: 3. Saturation states of product minerals and reaction paths

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