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

2015 ◽  
Vol 12 (22) ◽  
pp. 6791-6808 ◽  
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 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.

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

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.

Measuring silicate mineral dissolution rates using Si isotope doping

2016 ◽  
Vol 445 ◽  
pp. 146-163 ◽  
Author(s):  
Chen Zhu ◽  
Zhaoyun Liu ◽  
Yilun Zhang ◽  
Chao Wang ◽  
Augustus Scheafer ◽  
...  
Keyword(s):  
Mineral Dissolution ◽  
Silicate Mineral ◽  
Dissolution Rates ◽  
Si Isotope

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

2014 ◽  
Vol 78 (6) ◽  
pp. 1405-1416 ◽  
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.

Soil-solution chemistry in a low-elevation spruce-fir ecosystem, Howland, Maine

1995 ◽  
Vol 84 (1-2) ◽  
pp. 129-145 ◽  
Author(s):  
Ivan J. Fernandez ◽  
Gregory B. Lawrence ◽  
Yowhan Son
Keyword(s):  
Soil Solution ◽  
Solution Chemistry ◽  
Soil Solution Chemistry

scholarly journals Lithogenic hydrogen supports microbial primary production in subglacial and proglacial environments

2020 ◽  
Vol 118 (2) ◽  
pp. e2007051117
Author(s):  
Eric C. Dunham ◽  
John E. Dore ◽  
Mark L. Skidmore ◽  
Eric E. Roden ◽  
Eric S. Boyd
Keyword(s):  
Primary Production ◽  
Chemical Weathering ◽  
Enrichment Culture ◽  
Mineral Surfaces ◽  
Silicate Mineral ◽  
Weathering Processes ◽  
Order Of Magnitude ◽  
Lag Times ◽  
Carbonate Catchment ◽  
Physical And Chemical

Life in environments devoid of photosynthesis, such as on early Earth or in contemporary dark subsurface ecosystems, is supported by chemical energy. How, when, and where chemical nutrients released from the geosphere fuel chemosynthetic biospheres is fundamental to understanding the distribution and diversity of life, both today and in the geologic past. Hydrogen (H2) is a potent reductant that can be generated when water interacts with reactive components of mineral surfaces such as silicate radicals and ferrous iron. Such reactive mineral surfaces are continually generated by physical comminution of bedrock by glaciers. Here, we show that dissolved H2 concentrations in meltwaters from an iron and silicate mineral-rich basaltic glacial catchment were an order of magnitude higher than those from a carbonate-dominated catchment. Consistent with higher H2 abundance, sediment microbial communities from the basaltic catchment exhibited significantly shorter lag times and faster rates of net H2 oxidation and dark carbon dioxide (CO2) fixation than those from the carbonate catchment, indicating adaptation to use H2 as a reductant in basaltic catchments. An enrichment culture of basaltic sediments provided with H2, CO2, and ferric iron produced a chemolithoautotrophic population related to Rhodoferax ferrireducens with a metabolism previously thought to be restricted to (hyper)thermophiles and acidophiles. These findings point to the importance of physical and chemical weathering processes in generating nutrients that support chemosynthetic primary production. Furthermore, they show that differences in bedrock mineral composition can influence the supplies of nutrients like H2 and, in turn, the diversity, abundance, and activity of microbial inhabitants.

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