Geochemistry analysis and evolution of a bolson aquifer, basin and range province in the southwestern united states

Abstract

This paper expands significantly on the majorion geochemical characterization, evolution, and differentiation of groundwater in the Presidio-Redford Bolson (PRB) Aquifer of Texas as presented in Chowdhury et al. (2008). For 19 groundwater samples from the PRB Aquifer, the author calculated major cation-anion balance errors, equilibrium carbon dioxide partial pressure values and saturation indices for selected minerals. Comparison of major-ion analyses for groundwater from basin margin wells with those for basin center wells is documented and illustrated with ion-concentration maps and Piper and Stiff diagrams and reveals significant increases in concentrations of chloride, sulfate and sodium coupled with notable decrease of calcium in bolson-center well samples. These geochemical changes suggest dissolution of aquifer minerals and cation exchange as groundwater migrates downgradient to the bolson center. The US Geological Survey (USGS) computer code, NETPATH, was used to interpret probable net geochemical mass-balance reactions that potentially have occurred within the PRB Aquifer along groundwater flowpaths from bolson margin to bolson center. For all four upgradient-downgradient well pairs studied, at least three NETPATH models contain cation exchange values; calcium is being exchanged for sodium. The Rio Grande Alluvium Aquifer and Rio Grande River are notably minor sources of recharge to the PRB Aquifer, based on Chowdhury et al. (2008) and geochemical evaluations of this study.

Geochemical evaluation of high sulfate levels in Ponca Creek, northeastern Nebraska

“…The two times higher median pCO 2 value for Ponca Creek most likely is in part caused by its significantly higher dissolved solids content. This 2:1 ratio is consistent with the finding that pCO 2 increases with increasing concentrations of dissolved calcium carbonate, including HCO 3 (Foster, 1950;Plummer et al, 1976;Atkinson, 2011).…”

“…Piper diagrams (i.e., Figure 4) are not useful for the latter purpose because they illustrate percentages of major anions and cations-not concentrations of these ions. The size of the polygon creating the Stiff diagram is an indication of the TDS concentration (Bartos and Ogle, 2002;Atkinson, 2011). As sulfate concentrations in water increase, an increasing proportion of the SO 4 in solution becomes tied up in ion pairs (e.g., NaSO 4 , CaSO 4 ).…”

Baseline evaluation of legacy hydrochemical data for the Republican River watershed, southcentral Nebraska, USA

“…The USGS water-quality data evaluated for this study were downloaded from its historical water-data website in March 2019, which since then have been migrated to the Water Quality Portal (WQP), a cooperative service sponsored by the USGS and USEPA (WQP 2019). To evaluate and enhance major-ion data quality and usefulness, concentrations expressed in milliequivalents per liter (meq/L), cation-anion balance (CAB) errors, and numerous quality-assurance ratios (e.g., calculated TDS: measured TDS, (0.01) × (SC, in uS/cm): sum of anions in meq/L, (0.01) × (SC): sum of cations in meq/L), were used to evaluate major-ion data quality (Hem 1992;Atkinson 2011Atkinson , 2018Atkinson , 2019. The USGS considers ion balances within the ± 6% range to indicate major-ion analyses of useful quality; however, CABs up to 12% are still considered acceptable by the USGS (Bartos and Ogle 2002).…”

“…CAB errors for USGS analyses were significantly lower than those for NDEQ. For analyses that exceeded approximately 3% CAB errors, ion concentrations were revised appropriately using computerbased algorithms, e.g., (0.01) × (SC, in uS/cm) = sum of anions (in meq/L) (Atkinson, 2011(Atkinson, , 2018(Atkinson, , 2019, and revisions were constrained by measured TDS concentrations, SC values, and several empirical water-quality ratios as described above.…”

Hydrochemical Characteristics and Evolution of Groundwater in the Alluvial Plain (Anqing Section) of the Lower Yangtze River Basin: Multivariate Statistical and Inversion Model Analyses

“…By extracting the mathematical characteristics of data and ignoring the evolution mechanism of hydrochemical components, water quality factors can be described regionally to study the spatiotemporal distribution of the hydrochemical characteristics of groundwater, evaluate water quality, and identify influencing factors [15][16][17][18][19]. Integrating hydrochemical interpretation with inverse modeling, models with high confidence levels can be applied to quantitatively identify hydrochemical processes along a flow path [20,21]. Inverse geochemical modeling in PHREEQC [22] is based on a geochemical mole-balance model, which calculates phase mole transfer (moles of minerals and gases that must enter or leave a solution) to account for differences in initial and final water compositions along a flow path in a groundwater system.…”