Impacts of NO2 Impurities on the Indigenous Microbial Community Structure and Diversity in CO2-Saline-Sandstone Interaction System

Laboratory experiments (150 days) were performed to analyze the influence of NO2 impurities on indigenous microbial communities and diversity with 16S rRNA sequence at real GCS site (Geological CO2 Sequestration, ordos, China) conditions (pressure: 15 MPa, temperature: 55 °C). The possible impact of metabolic activity on the GCS process was investigated through the BLASTn search. Compared with the pure CO2, results demonstrate that the biomass and biodiversity were lower, due to the lower pH, within 60 days after the co-injection of 0.1% NO2. Subsequently, the pH was quickly buffered through the corrosion of feldspar and clay, and the impact of NO2 had almost no obvious effect on the microbial structure except the abundance of phylum and genus after 90 days. In addition, acid-producing bacteria appeared after 60 days, such as Bacillus, Acinetobacter, and Lactococcus, etc., lower the pH in the solution and accelerate the dissolution of minerals. The Fe (III)-reducing microbes Citrobacter freundii reduce the Fe (III) released from minerals to Fe (II) and induce siderite (FeCO3) biomineralization through biogeochemical processes. Therefore, the co-injection of trace NO2 will not significantly affect the growth of microorganisms on long timescale.

Numerical Phase-Field Model Validation for Dissolution of Minerals

Modelling of a mineral dissolution front propagation is of interest in a wide range of scientific and engineering fields. The dissolution of minerals often involves complex physico-chemical processes at the solid–liquid interface (at nano-scale), which at the micro-to-meso-scale can be simplified to the problem of continuously moving boundaries. In this work, we studied the diffusion-controlled congruent dissolution of minerals from a meso-scale phase transition perspective. The dynamic evolution of the solid–liquid interface, during the dissolution process, is numerically simulated by employing the Finite Element Method (FEM) and using the phase–field (PF) approach, the latter implemented in the open-source Multiphysics Object Oriented Simulation Environment (MOOSE). The parameterization of the PF numerical approach is discussed in detail and validated against the experimental results for a congruent dissolution case of NaCl (taken from literature) as well as on analytical models for simple geometries. In addition, the effect of the shape of a dissolving mineral particle was analysed, thus demonstrating that the PF approach is suitable for simulating the mesoscopic morphological evolution of arbitrary geometries. Finally, the comparison of the PF method with experimental results demonstrated the importance of the dissolution rate mechanisms, which can be controlled by the interface reaction rate or by the diffusive transport mechanism.

Contamination risk assessment of the Transboundary Zeravshan River using chemical and isotopic studies

The results of chemical and isotope analyses of water of the Zeravshan River are presented. Results show that the low salinity of the river water in the upstream reach is formed mainly by water dissolution of minerals in natural rocks, i.e. the existence of a water-rock interaction process. The detection of heavy cations in the composition of the river water is due to their transport long distances in the form of microparticles by wind and accumulation in snow cover and glaciers. During the melting of snow and glaciers, and during rain events, pollutants are carried by streams, small rivers, and finally by Zeravshan River that distributes the pollutants over long distances.