Particle fluxes in groundwater change subsurface shale rock chemistry over geologic time

Kim, Hyojin; Gu, Xiaoxiong; Brantley, Susan L.

doi:10.1016/j.epsl.2018.07.031

Cited by 18 publications

(21 citation statements)

References 44 publications

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“…The mechanisms that regulate DOC C-Q patterns -seasonally variable hydrological connectivity and groundwater contribution -are consistent with previous literature on geogenic species (Mn, Fe), isotopes, and particle fluxes at Shale Hills (Herndon et al, 2018;Kim et al, 2018;Sullivan et al, 2016;Thomas et al, 2013). For example, Mn is associated with DOC via biotic cycling and storage in plant species, and Fe is associated with DOC via aqueous complexation.…”

Section: Regulation Of C-q Patternssupporting

confidence: 85%

“…In this version of Flux-PIHM, the deeper groundwater flow Q G is a separate input to the stream and is decoupled from the shallow soil water. This is supported by field data that show negligible seasonal varia-tion in groundwater chemistry (Jin et al, 2014;Thomas et al, 2013;Kim et al, 2018). The Q G is estimated using conductivity mass-balance hydrograph separation (Lim et al, 2005).…”

Section: The Biort-flux-pihm (Bfp) Modelmentioning

confidence: 69%

“…The use of RTMs complements statistical tools for the identification of influential factors (Correll et al, 2001;Herndon et al, 2015;Zarnetske et al, 2018). Historically, RTMs have been used in groundwater systems, where direct observations are particularly challenging (Kolbe et al, 2019;Li et al, 2009;. At the catchment scale, biogeochemical modules have been developed as add-ons to hydrological models.…”

Section: Introductionmentioning

confidence: 99%

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Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

Wen

Perdrial

Abbott

et al. 2020

Hydrol. Earth Syst. Sci.

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Abstract. Lateral carbon flux through river networks is an important and poorly understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. Using field measurements of daily stream discharge, evapotranspiration, and stream DOC concentration, we calibrated the catchment-scale biogeochemical reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport–Flux–Penn State Integrated Hydrologic Model, BFP), which met the satisfactory standard of a Nash–Sutcliffe efficiency (NSE) value greater than 0.5. We used the calibrated model to estimate and compare the daily DOC production rates (Rp; the sum of the local DOC production rates in individual grid cells) and export rate (Re; the product of the concentration and discharge at the stream outlet, or load). Results showed that daily Rp varied by less than an order of magnitude, primarily depending on seasonal temperature. In contrast, daily Re varied by more than 3 orders of magnitude and was strongly associated with variation in discharge and hydrological connectivity. In summer, high temperature and evapotranspiration dried and disconnected hillslopes from the stream, driving Rp to its maximum but Re to its minimum. During this period, the stream only exported DOC from the organic-poor groundwater and from organic-rich soil water in the swales bordering the stream. The DOC produced accumulated in hillslopes and was later flushed out during the wet and cold period (winter and spring) when Re peaked as the stream reconnected with uphill and Rp reached its minimum. The model reproduced the observed concentration–discharge (C–Q) relationship characterized by an unusual flushing–dilution pattern with maximum concentrations at intermediate discharge, indicating three end-members of source waters. A sensitivity analysis indicated that this nonlinearity was caused by shifts in the relative contribution of different source waters to the stream under different flow conditions. At low discharge, stream water reflected the chemistry of organic-poor groundwater; at intermediate discharge, stream water was dominated by the organic-rich soil water from swales; at high discharge, the stream reflected uphill soil water with an intermediate DOC concentration. This pattern persisted regardless of the DOC production rate as long as the contribution of deeper groundwater flow remained low (<18 % of the streamflow). When groundwater flow increased above 18 %, comparable amounts of groundwater and swale soil water mixed in the stream and masked the high DOC concentration from swales. In that case, the C–Q patterns switched to a flushing-only pattern with increasing DOC concentration at high discharge. These results depict a conceptual model that the catchment serves as a producer and storage reservoir for DOC under hot and dry conditions and transitions into a DOC exporter under wet and cold conditions. This study also illustrates how different controls on DOC production and export – temperature and hydrological flow paths, respectively – can create temporal asynchrony at the catchment scale. Future warming and increasing hydrological extremes could accentuate this asynchrony, with DOC production occurring primarily during dry periods and lateral export of DOC dominating in major storm events.

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Section: Regulation Of C-q Patternssupporting

confidence: 85%

Section: The Biort-flux-pihm (Bfp) Modelmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

Wen

Perdrial

Abbott

et al. 2020

Hydrol. Earth Syst. Sci.

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“…Second, the additional source of sediment that must be activated to maintain concentrations during the falling limb is the result of slopewash (Larsen et al, 1999) and particle movement via subsurface seepage. Recent evidence demonstrates the mobilization of particles can occur within the subsurface (Herndon et al, 2018;Kim et al, 2018), a finding that challenges previously held models that particles in the soil profile are assumed to be difficult to transport. Our field observations show that seepage of groundwater or shallow interflow can occur at many points along the stream banks within the RI watershed.…”

Section: Discussionmentioning

confidence: 82%

Hysteretic Response of Solutes and Turbidity at the Event Scale Across Forested Tropical Montane Watersheds

et al. 2019

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Concentration-discharge relationships are a key tool for understanding the sources and transport of material from watersheds to fluvial networks. Storm events in particular provide insight into variability in the sources of solutes and sediment within watersheds, and the hydrologic pathways that connect hillslope to stream channel. Here we examine high-frequency sensor-based specific conductance and turbidity data from multiple storm events across two watersheds (Quebrada Sonadora and Rio Icacos) with different lithology in the Luquillo Mountains of Puerto Rico, a forested tropical ecosystem. Our analyses include Hurricane Maria, a category 5 hurricane. To analyze hysteresis, we used a recently developed set of metrics to describe and quantify storm events including the hysteresis index (HI), which describes the directionality of hysteresis loops, and the flushing index (FI), which can be used to infer whether the mobilization of material is source or transport limited. We also examine the role of antecedent discharge to predict hysteretic behavior during storms. Overall, specific conductance and turbidity showed contrasting responses to storms. The hysteretic behavior of specific conductance was similar across sites, displaying clockwise hysteresis and a negative FI indicating proximal sources of solutes and consistent source limitation. In contrast, the directionality of turbidity hysteresis was significantly different between watersheds, although both had strong flushing behavior indicative of transport limitation. Overall, models that included antecedent discharge did not perform any better than models with peak discharge alone, suggesting that the magnitude and trajectory of an individual event was the strongest driver of material flux and hysteretic behavior. Hurricane Maria produced unique hysteresis metrics within both watersheds, indicating a distinctive response to this major hydrological event. The similarity in response of specific conductance to storms suggests that solute sources and pathways are similar in the two watersheds. The divergence in behavior for turbidity suggests that sources and pathways of particulate matter vary between the two watersheds. The use of high-frequency sensor data allows the quantification of storm events while index-based metrics of hysteresis allow for the direct comparison of complex storm events across a heterogeneous landscape and variable flow conditions.

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“…However, soil and sediment particles also move below the land surface and even below the soil layer. Subsurface particle transport has been discussed by geomorphologists (e.g., Dunne, 1990), but weathering implications have only been highlighted in a few locations (e.g., Bern et al, 2015;Kim et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Subsurface particle transport shapes the deep critical zone in a granitoid watershed

Gu¹,

Kim²,

Hynek³

et al. 2021

Geochem. Persp. Let.

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Understanding the inter-relationships between chemical weathering and physical erosion remains a first order puzzle in Earth surface dynamics. In the Río Icacos watershed in the Luquillo Critical Zone Observatory, Puerto Rico, where some of the world's fastest weathering of granitoid watersheds has been measured, we show that chemical weathering not only releases dissolved solutes, but also weakens the rock around the fractures until particles detach and are mobilised by subsurface flow through fractures. These sand-sized particles are more weathered than corestones, but much less weathered than soils/saprolites. Subsurface removal of these clayenriched, magnetite-depleted particles from the fractures could explain zones with enhanced magnetic susceptibility and decreased terrain conductivity that are observed in geophysical surveys. Subsurface particle transport may thus contribute to geophysical signatures and help sustain high weathering fluxes at Río Icacos and other steep and highly fractured landscapes.

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Particle fluxes in groundwater change subsurface shale rock chemistry over geologic time

Cited by 18 publications

References 44 publications

Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

Hysteretic Response of Solutes and Turbidity at the Event Scale Across Forested Tropical Montane Watersheds

Subsurface particle transport shapes the deep critical zone in a granitoid watershed

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