Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)
Loading...
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Biogeosciences
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.
Description
Keywords
Silicate mineral, Physical weathering, Soil evolution model
Citation
Opolot, E., & Finke, P. A. (2015). Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2. 25). Biogeosciences, 12(22), 6791-6808. doi:10.5194/bg-12-6791-2015