Spatial Assessment of Hydrochemical Characteristics and Evolution of Inferior Quality Water in Kashi Delta

Hydrochemistry is a critical indicator of water quality. We analysed 146 hydrochemical parameters of groundwater and the hydrogeological background of the Kashi region in China, examined their spatial distributions, and elucidated the mechanisms of their occurrence. We used graphical and multivariate statistical methods to distinguish between high- and poor-quality water. In the Kizil-Cakmak River Basin of the northern Kashi region, the primary cations were Ca2+ and Mg2+, and the primary anion was SO42−; their concentrations were four times higher than the Class III water quality standard. Additionally, the salinity was high. In contrast, in the upstream and midstream parts of the Gez-Kushan River Basin in the southern Kashi region, the primary ions were HCO3− and SO42−, and the salinity was low. Downstream of the Gez-Kushan River Basin, the primary ion was Cl−, and the salinity was low. There was a wide-ranging spatial variability in the SO42−, Cl−, and Ca2+ contents throughout the study area. The present findings can be applied to locate suitable domestic, agricultural, and industrial water sources in the Kashi region and can provide theoretical guidance for the scientific development and management of groundwater in this region.

Predicting the impact of aqueous ions on fate and transport of munition compounds

A model framework for natural water has been developed using computational chemistry techniques to elucidate the interactions between solvated munition compounds and eight common ions in naturally occurring water sources. The interaction energies, residence times, coordination statistics, and surface preferences of nine munition related compounds with each ion were evaluated. The propensity of these interactions to increase degradation of the munition compound was predicted using accelerated replica QM/MM simulations. The degradation prediction data qualitatively align with previous quantum mechanical studies. The results suggest that primary ions of interest for fate and transport modeling of munition compounds in natural waters may follow the relative importance of SO₄²⁻, Cl⁻ ≫ HCO₃⁻, Na⁺, Mg²⁺ > Ca²⁺, K⁺, and NH₄⁺.

Water Radical Cations in the Gas Phase: Methods and Mechanisms of Formation, Structure and Chemical Properties

Water radical cations, (H2O)n+•, are of great research interest in both fundamental and applied sciences. Fundamental studies of water radical reactions are important to better understand the mechanisms of natural processes, such as proton transfer in aqueous solutions, the formation of hydrogen bonds and DNA damage, as well as for the discovery of new gas-phase reactions and products. In applied science, the interest in water radicals is prompted by their potential in radiobiology and as a source of primary ions for selective and sensitive chemical ionization. However, in contrast to protonated water clusters, (H2O)nH+, which are relatively easy to generate and isolate in experiments, the generation and isolation of radical water clusters, (H2O)n+•, is tremendously difficult due to their ultra-high reactivity. This review focuses on the current knowledge and unknowns regarding (H2O)n+• species, including the methods and mechanisms of their formation, structure and chemical properties.

Contributions to the Interpretation of Mass Spectrum of Tetraethoxysilane (TEOS). III. Accurate mass and M+1, M+2 isotopic effect measurements

The aim of this article in continuation of Parts I [1] and II [2] is the interpretation of the TEOS mass spectrum as a precursor in the sol-gel process. In Part I [1] the primary fragmentation ions at masses 207, 193, 179 and 163 were obtained experimentally by B/E linked scan by radical induced fragmentation reactions. In Part II [2] eliminations of neutral fragments from the primary ions and the obtained ions by consecutive elimination reactions were evidenced experimentally by the B/E and B/E(1-E)1/2 linked scans. In this third and final Part of interpretation of the TEOS mass spectrum, the separation of ions by mass spectrometry at high resolutions of 5000 and 6600, relative to standard resolution 1000, and measurements of the M+1 and M+2 isotopic effects at the resolution of 5000 are presented. The separation of the ions with nominal mass 105 at high resolution is detailed.

Contributions to the Interpretation of Mass Spectrum of Hexaethoxydisiloxane Linked scans and M+1, M+2 isotopic effects

The aim of this article is the study of the fragmentation reactions of hexaethoxydisiloxane initiated by electronic impact in the ionization chamber of a double focusing mass spectrometer. The initiation center of fragmentation reactions is established by quantum calculations. The daughter ions of hexaethoxydisiloxane molecular ion are obtained by linked scan B/E. The primary fragmentation ions with the masses 341, 297, 296 and 269 were obtained experimentally by B/E linked scan by radical induced fragmentation reactions. The eliminations of neutral fragments such as hydrogen, acetaldehyde, ethylene and water from the primary ions and the obtained ions by consecutive elimination reactions were emphasized experimentally by the B/E(1-E)1/2 linked scan by charge induced reactions.

Detection of lithium in scalp hair by time-of-flight secondary ion mass spectrometry with high energy (MeV) primary ions

The application of MeV-SIMS is presented for the detection and mapping of lithium in chemically unprocessed, longitudinally sectioned scalp hair.