Knowledge graph centered on HydroMix with 29 nodes and 93 connections. Top connected: Gothic, Crested Butte, East River, Gunnison, Pinus ponderosa.
Method synopsis
Combined use of major ion chemistry and Sr isotope signatures to identify distinct groundwater end members and quantify their contributions to stream flow using PCA-based end member mixing analysis.
Synthesized from method descriptions across 2 papers using this protocol.
Procedure from a recent peer-reviewed implementation
Samples from groundwater springs and near-stream piezometer were used to represent end member inputs to stream water. Only one sample was collected from each end member. One groundwater spring was located on a fractured hillslope, and the other groundwater spring was located within a dense spring network. The topographic position and geochemistry of these samples suggest that the fractured hillslope spring represents shallow, subsurface flow and the spring network represents deeper, older subsurface flow.
Quantities: One sample collected from each of two groundwater springs representing quick flow and slow flow end membersDuration: Single collection during summer 2021Conditions: Representative sampling from springs with different hydrologic characteristics
Equipment: sampling equipment for spring water collection
Conduct Sr isotope analysis
For Sr isotopic analysis, the filtered and acidified cation samples were used. Sr concentrations were evaluated to provide insight into water source contribution to the stream. 87Sr/86Sr ratios were measured and sample 87Sr/86Sr ratios were normalised to a NIST987 value of 0.710245. Sr was separated from other elements using Sr resin (Eichrom Technologies Inc.) on miniature Teflon columns. The end members and stream samples were analysed for Sr isotopes and concentrations.
Quantities: Sr isotope analysis conducted on subset of samples for end member identificationDuration: Laboratory analysis following initial chemical analysisConditions: Mass spectrometry laboratory conditions
Equipment: Sr resin (Eichrom Technologies Inc.), miniature Teflon columns, mass spectrometry equipment
Perform compositional PCA and end member mixing analysis
Principal components analysis (PCA) was used to evaluate spatial and temporal trends in geochemical data. Data were transformed into compositional units by converting all sample concentrations to milliequivalents and then dividing each solute concentration by the sum of all solute concentrations for a given sample. PCA-based end member mixing analysis (EMMA) was used to quantify end member contribution to Coal Creek samples. Stream samples not constrained by end members were removed from analysis.
Quantities: Analysis conducted on all stream chemistry data with three end members identifiedDuration: Data analysis phase following laboratory resultsConditions: Statistical analysis using R software
Equipment: R statistical software, robCompositions package