Differential weathering of basaltic and granitic catchments from concentration–discharge relationships

Ibarra, Daniel E.; Caves, Jeremy K.; Moon, Seulgi; Thomas, Dana L.; Hartmann, Jens; Chamberlain, C. Page; Maher, Kate

doi:10.1016/j.gca.2016.07.006

Cited by 128 publications

(172 citation statements)

References 203 publications

(445 reference statements)

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“…For these three sampling stations, we examined concentration vs discharge plots using q in log scale as the horizontal axis variable. For each watershed and solute, we estimated the solute production using the model of Maher and Chamberlain (2014) as discussed in Ibarra et al (2016) …”

Section: Hydrologic Data and Flux Calculationsmentioning

confidence: 99%

“…The high D w value at LNS-1 is consistent with elevated concentrations during the monsoon time when compared to other sites. Catchments with higher D w values, such as those in rapidly eroding mountains, can be interpreted to be more efficient at generating solutes and elevated C max concentration (Maher and Chamberlain, 2014;Ibarra et al, 2016).…”

Section: Concentration-discharge Relationshipsmentioning

confidence: 99%

“…The Si-D w value for LNS-1 is 4.08 m/yr higher than the mean Si-D w value of 3.47 m/yr identified for basaltic catchments and much higher than the mean Si-D w value of 1.49 m/yr for granitic catchments (c.f., Ibarra et al, 2016), suggesting intense weathering at the base of the Himalaya with respect to silica mobilization. Higher D w values at the base of the Himalaya for both * Sbcat car and * Sbcat sil ( Figure S5) are probably due to the combination of higher reaction rates and flow paths properties (Maher and Chamberlain, 2014).…”

Section: Concentration-discharge Relationshipsmentioning

confidence: 99%

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Seasonal variations of biogeochemical matter export along the Langtang-Narayani river system in central Himalaya

Bhatt

Hartmann

Acevedo

2018

Geochimica et Cosmochimica Acta

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Weathering and suspended matter fluxes of the Langtang Narayani river system in central Nepal Himalaya have been investigated at 16 stations for one year, based on monthly water sampling in the lower reaches and bi-monthly in higher elevation areas, to determine temporal variations of weathering fluxes along an elevation profile between 169 and 3989 m asl. Results indicate that the lower reaches are the dominant places of weathering in the system. The sum of major base cation fluxes is 2.9 to 9.2 higher during the monsoon season compared to the pre-monsoon season. Alkalinity and sea-salt corrected sulfate were the dominant anions (97%). The lowest downstream location exports 1611 tons km À2 yr À1 suspended sediment, 78.56 tons km À2 yr À1 of major cations (Na + K + Mg + Ca), 12.72 tons km À2 yr À1 of silica (4-fold higher than at the middle reaches of the basin), and 1.9 Â 10 6 mol km À2 yr À1 of dissolved inorganic carbon (8.9-fold higher than at the middle reaches). Nitrogen and phosphorus concentrations are low in general and dissolved organic carbon export is within expected ranges. River water pCO 2 values are low in general, with exception of those main stem reaches where tributaries with relevant pyrite oxidation processes, and lower pH, alter the pattern locally. Element ratios suggest seasonal shifts in the weathering flux generation, modulated by the monsoon system. During the peak of the monsoon season the most relevant weathering products alkalinity, * SO 4 , * Ca and * Mg were not diluted, and increased concentrations observed at the lower reaches suggests an enhanced mobilization during this period of the year. Carbonate weathering exceeds silicate weathering along the drainage network and the carbonate-to silicate-cation mol ratio is 3.5 at the outlet. Sulfide oxidation probably enhances weathering rates besides the control of the soil-rock partial pressure of CO 2 . The ratio of the total alkalinity flux to sea-salt corrected sulfate equivalent flux at the base of the Himalaya at Narayanghat was 5.7. Sea-salt corrected sulfate equivalent export is about the same as the silicate cation-equivalent flux that leaves the system (98%). Therefore, further research on sulfur isotopes might be helpful to support the hypothesis that pyrite oxidation compensates for the idealized CO 2 -consumption by silicate weathering in the studied area.

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Section: Hydrologic Data and Flux Calculationsmentioning

confidence: 99%

Section: Concentration-discharge Relationshipsmentioning

confidence: 99%

Section: Concentration-discharge Relationshipsmentioning

confidence: 99%

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Seasonal variations of biogeochemical matter export along the Langtang-Narayani river system in central Himalaya

Bhatt

Hartmann

Acevedo

2018

Geochimica et Cosmochimica Acta

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“…Finally, we calculate Dw values, denoted hereafter as Dw avg , using average C-q pair datasets Gaillardet et al, 1999) for each individual river by rearranging equation (3) and assuming C max values as the 95 th percentile for each weathering solute following methods used in von Blanckenburg et al (2015) and . Note that in Ibarra et al (2016) the discharge-weighted mean concentrations were used, rather than arithmetic mean concentrations as used in von Blanckenburg et al…”

Section: Framework and Methodsmentioning

confidence: 99%

“…We fit concentration-discharge (C-q) relationships using both a power-law equation (e.g., and a solute production model Ibarra et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Ibarra¹

2018

Preprint

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Maintenance of a habitable planet requires connections and balance among Earth’s biogeochemical cycles. Further, the strength of the feedbacks and couplings determines the stability of conditions in the surface climate system necessary for the evolution of life. Records of Earth’s past climate, paleoclimate records, provide constraints beyond the reach of the instrumental record on the directionality, strength and co-evolution of key Earth system cycles. This includes the geologic carbon cycle, the water cycle and the planet’s energy balance. Crucially, the geography, topography and lithology of Earth’s continents have two important features that are the focus of this dissertation. First, the continents provide boundary conditions that determine global circulation and hydroclimate patterns that couple Earth’s water and carbon cycles (Chapters 1 and 2). Second, the land surface provides a stabilizing negative feedback in the form of silicate weathering fluxes (Chapters 3 and 4, and Appendix E), balancing the long-term carbon cycle through alkalinity and solute delivery to the oceans, and subsequent carbonate burial. In this dissertation I use data, observations and modeling to place mechanistic constraints on how interactions between Earth’s surface and long-term biogeochemical cycles maintain balance and habitable conditions in our climate system conducive for the evolution of life. Fundamental to understanding our climate system is predicting the anticipated sign of terrestrial hydroclimate change during periods of climatic change. To this end I have investigated the regional response of hydroclimate change using paleoclimate records from mid-latitude lake systems. First, in Chapter 1, I have developed an inverse model to quantify how a mid-latitude lake system in Asia, the Songliao Basin, responded to a transient warming event during the Cretaceous. This model was also applied to a Holocene ostracod record from Lake Miragoane, Haiti. Second, in Chapter 2, I compile spatial distributions and size estimates of pluvial lake systems in western North America during the Pliocene-Pleistocene. By imposing mass and energy balance constraints (sensu Budyko) I forward modeled lake area distributions to demonstrate that now-arid western North America was wetter during both past colder and warmer periods during the Pliocene-Pleistocene, a result not predicted for future warming scenarios. Geologic observations primarily suggest wetter conditions globally during warmer-than-present periods. Importantly, this observation is a requirement for the operation of the stabilizing negative feedback between silicate weathering and climate. Understanding the factors that control silicate weathering rates is fundamental to constraining the evolution of Earth’s carbon cycle over geologic timescales. One challenge for reconstructing past weathering rates is determining the reactivity of Earth’s surface. In Chapter 3 I have quantified the reactivity of modern basalt and granite catchments using a process-based solute production model and concentration-discharge weathering relationships. This approach provides mechanisms that link runoff (i.e., terrestrial hydroclimate changes that were the focus of Chapters 1 and 2) with the distribution of global sub-aerial silicate lithologies. In Chapter 4 I utilize an emerging metal isotope system, lithium isotopes, to investigate the terrestrial weathering response to a large perturbation in the carbon cycle during the Cretaceous. We determine that the background-state of the Cretaceous weathering system was more congruent and, hence, more sensitive to perturbations in the carbon cycle than during the Neogene. Finally, in Appendix E I have quantified how step-wise geologic evolution of land plants strengthened the silicate weathering feedback over the Phanerozoic. I have developed a new reactive transport framework for evaluating the relative plant-controlled roles of hydrologic versus thermodynamic mechanisms that influence the coupling between the water cycle and silicate weathering fluxes on a continental scale. The results described in this dissertation constrain links between two connected portions of the exogenic Earth system. I have provided constraints for how the land surface records past changes in regional atmospheric circulation patterns, as well as regional water and energy balances. Further, using reactive transport modeling, I have placed new constraints on the role of plants and lithology in determining the coupling between terrestrial hydroclimate and weathering. Collectively these results suggest that the surface Earth system, our planet’s fluid envelope, has been progressively tuned by the advent of continents and the evolution of life. [Note: this is the non-embargoed portion of my dissertation]

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Primary weathering rates, water transit times, and concentration‐discharge relations: A theoretical analysis for the critical zone

Ameli

Beven

Erlandsson

et al. 2017

Water Resources Research

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The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration‐discharge (C‐Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C‐Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (Ks) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration ( Ceq) to intrinsic weathering rate ( Rmax), vertical heterogeneity in Ks enhances the gradient of weathering‐derived solute concentration in the critical zone and strengthens the inverse stream C‐Q relation. As CeqRmax decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C‐Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in Ks. These findings suggest that the transport‐controlled mechanisms in the hillslope can lead to chemostatic C‐Q relations in the stream while the hillslope surface reaction‐controlled mechanisms are associated with an inverse stream C‐Q relation. In addition, as CeqRmax decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

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Differential weathering of basaltic and granitic catchments from concentration–discharge relationships

Cited by 128 publications

References 203 publications

Seasonal variations of biogeochemical matter export along the Langtang-Narayani river system in central Himalaya

Seasonal variations of biogeochemical matter export along the Langtang-Narayani river system in central Himalaya

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Primary weathering rates, water transit times, and concentration‐discharge relations: A theoretical analysis for the critical zone

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