Distinct Source Water Chemistry Shapes Contrasting Concentration‐Discharge Patterns

Abstract

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.

Nitrate removal and young stream water fractions at the catchment scale

“…In fact, flow integration across depths can explain the concentration variations in different flow regimes (Seibert et al, 2009; van der Velde et al, 2010). This vertical stratification depends on lithology, the depth and characteristics of fractured rocks, and ultimately the vertical connectivity (Kolbe et al, 2019; Zhi et al, 2019) of subsurface systems. The “flushing” export patterns has been observed not only for nitrate but also for other solutes that are enriched in shallow soils and depleted in deeper subsurface, including dissolved organic carbon (DOC) (Moatar, Abbott, Minaudo, Curie, & Pinay, 2017; Musolff et al, 2017; Trauth et al, 2018; Zarnetske, Bouda, Abbott, Saiers, & Raymond, 2018).…”

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

“…The code includes three modules ( Figure 2): the surface hydrological module PIHM, the landsurface module Flux, and the multicomponent reactive transport module BioRT (Biogeochemical Reactive Transport). The code has been applied to simulate conservative solute transport, mineral dissolution, chemical weathering, surface complexation, and biogeochemical reactions at the catchment scale (Bao et al, 2017;Zhi et al, 2019;. Here we only introduce the salient features of the code that are relevant to this study; readers are referred to earlier publications for details on the code.…”

“…In this context, we have developed a catchment-scale reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport -Flux -Penn State Integrated Hydrologic Modeling System, BFP), hereafter referred to as BFP (Bao et al, 2017;Zhi et al, 2019). The model integrates catchment hydrological and biogeochemical processes.…”

Enantiomeric effect of paclobutrazol on the microorganism composition during wine fermentation

“…Nevertheless, pesticide residues have always been the focus of attention because of the toxicity to nontarget organisms and human. Some studies have reported that pesticides could be found and detected in many agricultural products, especially vegetables and fruits . Wine fermented from grapes has a long history in the world and is very popular among consumers.…”

“…Some studies have reported that pesticides could be found and detected in many agricultural products, especially vegetables and fruits. [1][2][3] Wine fermented from grapes has a long history in the world and is very popular among consumers. To our knowledge, the wine fermentation process is mediated by fermentation microbial and the quality of wine could be affected by microbial.…”