Measuring silicate mineral dissolution rates using Si isotope doping

Abstract. Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic soil evolution models. This study applies a mechanistic soil evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other soil-forming processes and factors. The SoilGen soil evolution model is a 1-D model developed to simulate the time-depth evolution of soil properties as a function of various soil-forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling, and bioturbation) driven by soil-forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the soil solution composition play an equally important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates possibly due to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore a need to include secondary mineral precipitation mechanism in our formulation. In addition, there is a need for a more detailed study that is specific to field sites with detailed measurements of silicate mineral dissolution rates, climate, hydrology, and mineralogy to enable the calibration and validation of the model. Nevertheless, this study is another important step to demonstrate the critical need to couple different soil-forming processes with chemical weathering in order to explain differences observed between laboratory and field measured silicate mineral dissolution rates.

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Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)

Biogeosciences Discussions ◽

10.5194/bgd-12-13887-2015 ◽

2015 ◽

Vol 12 (16) ◽

pp. 13887-13929

Author(s):

E. Opolot ◽

P. A. Finke

Keyword(s):

Soil Solution ◽

Chemical Weathering ◽

Evolution Model ◽

Solution Chemistry ◽

Mineral Dissolution ◽

Silicate Mineral ◽

Dissolution Rates ◽

Soil Evolution ◽

Physical Weathering ◽

Soil Forming Processes

Abstract. Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic soil evolution models. This study applies a mechanistic soil evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other soil forming processes and factors. The SoilGen soil evolution model is a 1-D model developed to simulate the time-depth evolution of soil properties as a function of various soil forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling and bioturbation) driven by soil forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the soil solution composition equally play an important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates owing to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore need to include secondary mineral precipitation mechanism in our formulation. In addition, there is need for a more detailed study that is specific to field sites with detailed measurements of silicate mineral dissolution rates, climate, hydrology and mineralogy to enable the calibration and validation of the model. Nevertheless, this study is another important step to demonstrate the critical need to couple different soil forming processes with chemical weathering in order to explain differences observed between laboratory and field measured silicate mineral dissolution rates.

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Quantum chemical studies of the effects on silicate mineral dissolution rates by adsorption of alkali metals

Geochimica et Cosmochimica Acta ◽

10.1016/s0016-7037(97)00118-x ◽

1997 ◽

Vol 61 (13) ◽

pp. 2577-2587 ◽

Cited By ~ 24

Author(s):

Helene Strandh ◽

Lars G.M. Pettersson ◽

Lennart Sjöberg ◽

Ulf Wahlgren

Keyword(s):

Quantum Chemical ◽

Alkali Metals ◽

Mineral Dissolution ◽

Silicate Mineral ◽

Dissolution Rates ◽

Chemical Studies ◽

Quantum Chemical Studies

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Temporal and Spatial Heterogeneity of Mineral Dissolution Rates in Fractured Media

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2021.08.008 ◽

2021 ◽

Author(s):

Elizabeth Andrews ◽

Alexis Navarre-Sitchler

Keyword(s):

Spatial Heterogeneity ◽

Fractured Media ◽

Mineral Dissolution ◽

Dissolution Rates ◽

Temporal And Spatial ◽

Temporal And Spatial Heterogeneity

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The experimental determination of hydromagnesite precipitation rates at 22.5–75ºC

Mineralogical Magazine ◽

10.1180/minmag.2014.078.6.07 ◽

2014 ◽

Vol 78 (6) ◽

pp. 1405-1416 ◽

Cited By ~ 11

Author(s):

U.-N. Berninger ◽

G. Jordan ◽

J. Schott ◽

E. H. Oelkers

Keyword(s):

Low Temperature ◽

Experimental Determination ◽

Closed System ◽

Equilibrium Constants ◽

Magnesium Silicate ◽

Silicate Mineral ◽

Dissolution Rates ◽

Dissolution And Precipitation

Natural hydromagnesite (Mg5(CO3)4(OH)2·4H2O) dissolution and precipitation experiments were performed in closed-system reactors as a function of temperature from 22.5 to 75ºC and at 8.6 < pH < 10.7. The equilibrium constants for the reaction Mg5(CO3)4(OH)2·4H2O + 6H+ = 5Mg2+ + 4HCO3– + 6H2O were determined by bracketing the final fluid compositions obtained from the dissolution and precipitation experiments. The resulting constants were found to be 1033.7±0.9, 1030.5±0.5 and 1026.5±0.5 at 22.5, 50 and 75ºC, respectively. Whereas dissolution rates were too fast to be determined from the experiments, precipitation rates were slower and quantified. The resulting BET surface areanormalized hydromagnesite precipitation rates increase by a factor of ~2 with pH decreasing from 10.7 to 8.6. Measured rates are approximately two orders of magnitude faster than corresponding forsterite dissolution rates, suggesting that the overall rates of the low-temperature carbonation of olivine are controlled by the relatively sluggish dissolution of the magnesium silicate mineral.

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Latent disciplinal clashes concerning the batch dissolution of minerals, and their wider implications

Environmental Chemistry ◽

10.1071/en17199 ◽

2018 ◽

Vol 15 (2) ◽

pp. 113 ◽

Cited By ~ 2

Author(s):

Victor W. Truesdale ◽

Jim Greenwood

Keyword(s):

Large Scale ◽

Dissolution Kinetics ◽

Mineral Dissolution ◽

Atomic Scale ◽

Rate Equations ◽

Silicate Mineral ◽

Waste Products ◽

Calcite Dissolution ◽

Macro Scale ◽

Made In

Environmental contextMineral dissolution kinetics are important to understand natural processes including those increasingly used to store waste carbon dioxide and highly radio-active nuclides, and those involved in the amelioration of climate change and sea-level rise. We highlight a mistake made in the fundamental science that has retarded progress in the field for over 40 years. Its removal suggests improved ways to approach dissolution studies. AbstractMineral dissolution kinetics are fundamental to biogeochemistry, and to the application of science to reduce the deleterious effects of humanity’s waste products, e.g. CO2 and radio-nuclides. However, a mistake made in the selection of the rate equation appropriate for use at the macro-scale of the aquatic environment has stymied growth in major aspects of the subject for some 40 years. This paper identifies the mistake, shows how it represents a latent disciplinal clash between two rate equations, and explores the misunderstandings that resulted from it. The paper also briefly explores other disciplinal clashes. Using the example of calcite dissolution, the paper also shows how the phenomenon of ‘non-ideal’ dissolution, which is prevalent in alumino-silicate mineral dissolution, as well as with calcite, has obscured the clash. The paper provides new information on plausible mechanisms, the absence of which has contributed to the problem. Finally, it argues that disciplinal clashes need to be minimised so that a rigorous description of dissolution at the large scale can be matched to findings at the atomic, or near-atomic, scale.

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The scaling of mineral dissolution rates under complex flow conditions

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2020.01.048 ◽

2020 ◽

Vol 274 ◽

pp. 63-78 ◽

Cited By ~ 1

Author(s):

Rong Li ◽

Chen Yang ◽

Dongfang Ke ◽

Chongxuan Liu

Keyword(s):

Mineral Dissolution ◽

Flow Conditions ◽

Complex Flow ◽

Dissolution Rates

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Geochemistry of contrasting stream types, Taylor Valley, Antarctica

Geological Society of America Bulletin ◽

10.1130/b35479.1 ◽

2020 ◽

Vol 133 (1-2) ◽

pp. 425-448

Author(s):

Russell S. Harmon ◽

Deborah L. Leslie ◽

W. Berry Lyons ◽

Kathleen A. Welch ◽

Diane M. McKnight

Keyword(s):

Dissolved Oxygen ◽

Austral Summer ◽

Mineral Dissolution ◽

Silicate Mineral ◽

Cation Composition ◽

Taylor Valley ◽

Low Concentrations ◽

Hyporheic Zones ◽

Dry Valley ◽

Geochemical Fingerprint

Abstract The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Ephemeral streams flow here during the austral summer, transporting glacial meltwater to perennially ice-covered, closed basin lakes. The chemistry of 24 Taylor Valley streams was examined over the two-decade period of monitoring from 1993 to 2014, and the geochemical behavior of two streams of contrasting physical and biological character was monitored across the seven weeks of the 2010–2011 flow season. Four species dominate stream solute budgets: HCO3–, Ca2+, Na+, and Cl–, with SO42–, Mg2+, and K+ present in significantly lesser proportions. All streams contain dissolved silica at low concentrations. Across Taylor Valley, streams are characterized by their consistent anionic geochemical fingerprint of HCO3 > Cl > SO4, but there is a split in cation composition between 14 streams with Ca > Na > Mg > K and 10 streams with Na > Ca > Mg > K. Andersen Creek is a first-order proglacial stream representative of the 13 short streams that flow <1.5 km from source to gage. Von Guerard is representative of 11 long streams 2–7 km in length characterized by extensive hyporheic zones. Both streams exhibit a strong daily cycle for solute load, temperature, dissolved oxygen, and pH, which vary in proportion to discharge. A well-expressed diurnal co-variation of pH with dissolved oxygen is observed for both streams that reflects different types of biological control. The relative consistency of Von Guerard composition over the summer flow season reflects chemostatic regulation, where water in transient storage introduced during times of high streamflow has an extended opportunity for water-sediment interaction, silicate mineral dissolution, and pore-water exchange.

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