An upscaled rate law for mineral dissolution in heterogeneous media: The role of time and length scales

Wen, Hang; Li, Li

doi:10.1016/j.gca.2018.04.024

Cited by 46 publications

(52 citation statements)

References 95 publications

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“…More fractured regolith enables vertical flow from the shallow zone into deeper reservoirs, thereby increasing the connectedness and alleviating the differences between shallow and deep zones. Generally, lower permeability contrasts between reactive and nonreactive zones enhance the similarity of water chemistry (Wen & Li, , ; Wen et al, ). Musolff et al () represented catchment structural heterogeneity as mobile and immobile zones and analyzed several solutes in over 61 catchments.…”

Section: Discussionmentioning

confidence: 99%

“…The SSA of feldspars is reported to vary between 1.8 and 3.0 m 2 /g (Peckhaus et al, ), also higher than the calibrated 1.26 m 2 /g. The surface areas of natural materials that are actually reacting are often orders of magnitude lower than the measured absolute surface areas because hydrological conditions are dynamic and not all surface areas are reacting (Heidari et al, ; Wen & Li, ).…”

Section: Methodsmentioning

confidence: 99%

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Distinct Source Water Chemistry Shapes Contrasting Concentration‐Discharge Patterns

Zhi

Wang

et al. 2019

Water Resources Research

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113

166

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Understanding concentration‐discharge (C‐Q) relationships are essential for predicting chemical weathering and biogeochemical cycling under changing climate and anthropogenic conditions. Contrasting C‐Q relationships have been observed widely, yet a mechanistic framework that can interpret diverse patterns remains elusive. This work hypothesizes that seemingly disparate C‐Q patterns are driven by switching dominance of end‐member source waters and their chemical contrasts arising from subsurface biogeochemical heterogeneity. We use data from Coal Creek, a high‐elevation mountainous catchment in Colorado, and a recently developed watershed reactive transport model (BioRT‐Flux‐PIHM). Sensitivity analysis and Monte‐Carlo simulations (500 cases) show that reaction kinetics and thermodynamics and distribution of source materials across depths govern the chemistry gradients of shallow soil water and deeper groundwater entering the stream. The alternating dominance of organic‐poor yet geo‐solute‐rich groundwater under dry conditions and organic‐rich yet geo‐solute‐poor soil water during spring melt leads to the flushing pattern of dissolved organic carbon and the dilution pattern of geogenic solutes (e.g., Na, Ca, and Mg). In addition, the extent of concentration contrasts regulates the power law slopes (b) of C‐Q patterns via a general equation b=δb0.25emCratioCratio,1/2+Cratio+bmin. At low ratios of soil water versus groundwater concentrations (Cratio = Csw/Cgw < 0.6), dilution occurs; at high ratios (Cratio > 1.8), flushing arises; chemostasis occurs in between. This equation quantitatively interprets b values of 11 solutes (dissolved organic carbon, dissolved P, NO3−, K, Si, Ca, Mg, Na, Al, Mn, and Fe) from three catchments (Coal Creek, Shale Hills, and Plynlimon) of differing climate, geologic, and land cover conditions. This indicates potentially broad regulation of subsurface biogeochemical heterogeneity in determining C‐Q patterns and wide applications of this equation in quantifying b values, which can have broad implications for predicting chemical weathering and biogeochemical transformation at the watershed scale.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Distinct Source Water Chemistry Shapes Contrasting Concentration‐Discharge Patterns

Zhi

Wang

et al. 2019

Water Resources Research

Self Cite

113

166

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“…The field has also evolved from using stationary TTDs to the recent development of time‐variant TTD theory, which acknowledges the non‐stationary nature of hydrologic fluxes and water storage (Botter, Bertuzzo, & Rinaldo, 2011; Harman, 2015; Rinaldo et al, 2015; van der Velde, Torfs, van der Zee, & Uijlenhoet, 2012). The mean transit time is a useful property of age distributions and it has also been included in theories of reactive transport (see Maher, 2010; Wen & Li, 2018). However, there has been growing concern about the estimates of the mean transit time (or mean water age) in catchments.…”

Section: Introductionmentioning

confidence: 99%

“…Pinay et al (2015) suggests that the dimensionless number that quantifies the relative magnitude of reaction time with water transit time, for example, Damköhler number, is key to upscale denitrification rates in local hot spots to river basins. This recognition is vital not only for nitrate removal but also for other geochemical reactions such as chemical weathering, soil respiration, and decomposition of organic carbon (Ameli et al, 2017; Benettin, Bailey, et al, 2015; Musolff, Fleckenstein, Rao, & Jawitz, 2017; Wen & Li, 2018). Along with this recognition, there is growing consensus that multiple tracers can be used to infer different processes at the watershed scale (Abbott et al, 2016; Sprenger et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Nitrate removal and young stream water fractions at the catchment scale

Benettin

Fovet

2020

Hydrological Processes

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Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy-Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter-spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions. K E Y W O R D Sagricultural catchment, chloride transport, denitrification, Naizin, nitrate removal, SAS function, water age, young water fraction

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“…If the time it takes to reach equilibrium is longer than the time that water stays in a system, i.e., τ eq > τ r , solute concentrations leaving the system depend on flow rates; if τ eq < τ r , solutes reach and remain at equilibrium concentrations at the system outlet and do not vary with flow rates. In heterogeneous systems where fast-dissolving minerals (e.g., carbonate) reside in low-permeability zones and slow-dissolving minerals (e.g., quartz) in high permeability zones, solute concentrations and weathering rates have been shown to depend similarly on Damkohler number but need to additionally consider the relative magnitude (ratio) of the contact time between water and reacting minerals (τ ad,r ) versus the overall residence time in the entire domain (τ a ) (Wen and Li 2018). This is because only a fraction of water flow, not the total flow, channels through the low-permeability reactive zones and dissolves reacting minerals (Wen and Li 2017).…”

Section: Reaction Rates At the Watershed Scale: Linking Travel Time mentioning

confidence: 99%

Watershed Reactive Transport

2019

Reviews in Mineralogy and Geochemistry

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A watershed (also drainage basin, river basin, or catchment) is defined as "… the area that topographically appears to contribute all the water that passes through a specified cross section of a stream (the outlet)" (Dingman 2015). In this chapter, I choose to use the term "watershed" as it is a broadly used one; it should be understood more as small watersheds or catchments. Watersheds are the fundamental units that support river networks, the blood vessels at Earth's surface ultimately draining into the ocean. Watersheds are complex hydro-biogeochemical reactors. They receive water, mass, and energy, transport them to distinct compartments, and transform them into various forms (Fig.1). Hydrological processes partition precipitation to the atmosphere, to the ground surface, and to the subsurface, eventually entering streams. Similarly, plants translate sunlight, water, CO 2 , and nutrients into organic matters (leaves, stems, roots) that fall and deposit in soil. As water routes through soils, it interacts with roots, microbes, and reactive gases (i.e., CO 2 and O 2), releases solutes, and ultimately transporting them out of watersheds. The water flow (discharge) and solute concentrations measured at stream outlets therefore reflect convoluted signature of ecohydrological and biogeochemical coupling. The process interactions and feedbacks are dictated not only by hydroclimatic forcing but also the architecture of watersheds, in particular the above-ground characteristics such as land cover and surface topography, as well as the below-ground structure including soil depth, soil type, geology, and root architecture. The external forcing and internal idiosyncrasies dictate the magnitude, timing, and spatial distribution of water flow and chemistry (Chorover et al. 2011; Brooks et al. 2015), giving rise to non-linear emergent behaviors that are unique of watershed reactive transport processes. Understanding feedbacks and non-linearity requires process-based models that integrate multiple interacting processes. Such integration however does not come easily with traditional boundaries of hydrology versus biogeochemistry relevant disciplines. As will be discussed later in this chapter, relevant model development has been advancing along two separate lines: hydrology models that solve for water storage and fluxes at the watershed scale and beyond (Fatichi et al. 2016), and reactive transport models (RTMs) that center on aqueous and solid concentration changes arising from transport and multi-component biogeochemical reactions typically in "closed" groundwater systems without much interactions with "open" watersheds directly receiving precipitation and sun light (Steefel et al. 2015; Li et al. 2017b). This comes along with a history of hydrologists often trained as physicists studying fluid mechanics, and biogeochemists typically grow up as geologists, chemists, or environmental engineers. There are however considerable needs to reach beyond disciplinary boundaries and integrate the two lines to develop watershed reacti...

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An upscaled rate law for mineral dissolution in heterogeneous media: The role of time and length scales

Cited by 46 publications

References 95 publications

Distinct Source Water Chemistry Shapes Contrasting Concentration‐Discharge Patterns

Distinct Source Water Chemistry Shapes Contrasting Concentration‐Discharge Patterns

Nitrate removal and young stream water fractions at the catchment scale

Watershed Reactive Transport

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